first commit

core/modules/link/css/link.icon.theme.css

@@ -0,0 +1,9 @@
+/*
+ * DO NOT EDIT THIS FILE.
+ * See the following change record for more information,
+ * https://www.drupal.org/node/3084859
+ * @preserve
+ */
+.field-icon-link {
+  background-image: url("data:image/svg+xml,%3csvg height='38' viewBox='0 0 38 38' width='38' xmlns='http://www.w3.org/2000/svg'%3e%3cpath d='m25.84 2.37c-1.972.311-3.605 1.099-5.162 2.493-1.157 1.035-3.04 2.995-3.221 3.353a1.34 1.34 0 0 0 -.018 1.252c.193.415.819.997 1.219 1.133.798.272 1.01.143 2.997-1.818.891-.88 1.734-1.688 1.873-1.796.678-.523 1.686-.971 2.555-1.135.663-.125 2.055-.089 2.622.068 1.75.484 3.119 1.611 3.911 3.219.493.999.595 1.459.593 2.673-.002 1.102-.093 1.593-.444 2.395-.437.998-.716 1.326-3.528 4.137-1.468 1.467-2.844 2.795-3.058 2.951-1.167.846-2.819 1.293-4.162 1.126a6.606 6.606 0 0 1 -2.194-.674c-.836-.445-1.081-.654-2.231-1.909-.385-.42-.706-.585-1.139-.584-.431.001-.898.215-1.313.604-.579.541-.721 1.135-.423 1.773.157.339.916 1.282 1.378 1.712a9.753 9.753 0 0 0 3.617 2.108c.98.314 1.471.395 2.613.432.91.03 1.195.015 1.842-.096a9.098 9.098 0 0 0 2.767-.918c1.263-.639 1.688-1.007 4.862-4.201 2.382-2.397 2.954-3.006 3.28-3.496 1.732-2.599 2.122-5.727 1.075-8.622-1.126-3.113-3.765-5.388-7.049-6.079-.818-.172-2.484-.224-3.262-.101m-10.64 10.783c-1.249.2-2.102.463-3.071.946-1.308.651-1.648.941-4.727 4.012-1.669 1.666-2.97 3.018-3.178 3.302-.899 1.23-1.444 2.426-1.758 3.857-.168.763-.233 2.364-.128 3.113.583 4.136 3.564 7.335 7.605 8.161 2.581.528 5.344-.096 7.537-1.7.261-.191 1.234-1.1 2.162-2.02 1.865-1.851 2.043-2.083 2.047-2.677.003-.427-.133-.719-.538-1.163-.35-.383-.785-.62-1.212-.661-.581-.056-.836.131-2.744 2.013-1.74 1.715-2.089 2.001-2.908 2.379-.895.414-1.338.502-2.507.499-.947-.002-1.096-.018-1.592-.171-.737-.227-1.185-.431-1.713-.783-1.1-.731-1.953-1.812-2.37-3.006-.489-1.401-.452-3.071.097-4.364.449-1.056.614-1.252 3.451-4.107 1.466-1.475 2.829-2.809 3.03-2.964 1.652-1.284 3.976-1.616 5.891-.842 1.036.419 1.703.931 2.81 2.16.537.595 1.024.749 1.675.527.388-.132.966-.601 1.17-.951.338-.576.258-1.146-.258-1.835-1.526-2.036-3.759-3.341-6.333-3.703-.425-.06-2.108-.075-2.438-.022' fill='%2355565b'/%3e%3c/svg%3e");
+}

core/modules/link/css/link.icon.theme.pcss.css

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+.field-icon-link {
+  background-image: url(../../../misc/icons/55565b/link.svg);
+}

core/modules/link/link.info.yml

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+name: Link
+type: module
+description: 'Provides a field type for internal and external URLs.'
+package: Field types
+# version: VERSION
+dependencies:
+  - drupal:field
+
+# Information added by Drupal.org packaging script on 2024-07-04
+version: '10.3.1'
+project: 'drupal'
+datestamp: 1720094222

core/modules/link/link.libraries.yml

@@ -0,0 +1,7 @@
+drupal.link-icon:
+  version: VERSION
+  css:
+    theme:
+      css/link.icon.theme.css: {}
+  dependencies:
+    - field_ui/drupal.field_ui.manage_fields

core/modules/link/link.module

@@ -0,0 +1,77 @@
+<?php
+
+/**
+ * @file
+ * Defines simple link field types.
+ */
+
+use Drupal\Core\Field\FieldTypeCategoryManagerInterface;
+use Drupal\Core\Link;
+use Drupal\Core\Url;
+use Drupal\Core\Routing\RouteMatchInterface;
+
+/**
+ * Implements hook_help().
+ */
+function link_help($route_name, RouteMatchInterface $route_match) {
+  switch ($route_name) {
+    case 'help.page.link':
+      $output = '';
+      $output .= '<h2>' . t('About') . '</h2>';
+      $output .= '<p>' . t('The Link module allows you to create fields that contain internal or external URLs and optional link text. See the <a href=":field">Field module help</a> and the <a href=":field_ui">Field UI help</a> pages for general information on fields and how to create and manage them. For more information, see the <a href=":link_documentation">online documentation for the Link module</a>.', [':field' => Url::fromRoute('help.page', ['name' => 'field'])->toString(), ':field_ui' => (\Drupal::moduleHandler()->moduleExists('field_ui')) ? Url::fromRoute('help.page', ['name' => 'field_ui'])->toString() : '#', ':link_documentation' => 'https://www.drupal.org/documentation/modules/link']) . '</p>';
+      $output .= '<h2>' . t('Uses') . '</h2>';
+      $output .= '<dl>';
+      $output .= '<dt>' . t('Managing and displaying link fields') . '</dt>';
+      $output .= '<dd>' . t('The <em>settings</em> and the <em>display</em> of the link field can be configured separately. See the <a href=":field_ui">Field UI help</a> for more information on how to manage fields and their display.', [':field_ui' => (\Drupal::moduleHandler()->moduleExists('field_ui')) ? Url::fromRoute('help.page', ['name' => 'field_ui'])->toString() : '#']) . '</dd>';
+      $output .= '<dt>' . t('Setting the allowed link type') . '</dt>';
+      $output .= '<dd>' . t('In the field settings you can define the allowed link type to be <em>internal links only</em>, <em>external links only</em>, or <em>both internal and external links</em>. <em>Internal links only</em> and <em>both internal and external links</em> options enable an autocomplete widget for internal links, so a user does not have to copy or remember a URL.') . '</dd>';
+      $output .= '<dt>' . t('Adding link text') . '</dt>';
+      $output .= '<dd>' . t('In the field settings you can define additional link text to be <em>optional</em> or <em>required</em> in any link field.') . '</dd>';
+      $output .= '<dt>' . t('Displaying link text') . '</dt>';
+      $output .= '<dd>' . t('If link text has been submitted for a URL, then by default this link text is displayed as a link to the URL. If you want to display both the link text <em>and</em> the URL, choose the appropriate link format from the drop-down menu in the <em>Manage display</em> page. If you only want to display the URL even if link text has been submitted, choose <em>Link</em> as the format, and then change its <em>Format settings</em> to display <em>URL only</em>.') . '</dd>';
+      $output .= '<dt>' . t('Adding attributes to links') . '</dt>';
+      $output .= '<dd>' . t('You can add attributes to links, by changing the <em>Format settings</em> in the <em>Manage display</em> page. Adding <em>rel="nofollow"</em> notifies search engines that links should not be followed.') . '</dd>';
+      $output .= '<dt>' . t('Validating URLs') . '</dt>';
+      $output .= '<dd>' . t('All links are validated after a link field is filled in. They can include anchors or query strings.') . '</dd>';
+      $output .= '</dl>';
+      return $output;
+  }
+}
+
+/**
+ * Implements hook_theme().
+ */
+function link_theme() {
+  return [
+    'link_formatter_link_separate' => [
+      'variables' => ['title' => NULL, 'url_title' => NULL, 'url' => NULL],
+    ],
+  ];
+}
+
+/**
+ * Prepares variables for separated link field templates.
+ *
+ * This template outputs a separate title and link.
+ *
+ * Default template: link-formatter-link-separate.html.twig.
+ *
+ * @param array $variables
+ *   An associative array containing:
+ *   - title: (optional) A descriptive or alternate title for the link, which
+ *     may be different than the actual link text.
+ *   - url_title: The anchor text for the link.
+ *   - url: A \Drupal\Core\Url object.
+ */
+function template_preprocess_link_formatter_link_separate(&$variables) {
+  $variables['link'] = Link::fromTextAndUrl($variables['url_title'], $variables['url'])->toString();
+}
+
+/**
+ * Implements hook_field_type_category_info_alter().
+ */
+function link_field_type_category_info_alter(&$definitions) {
+  // The `link` field type belongs in the `general` category, so the libraries
+  // need to be attached using an alter hook.
+  $definitions[FieldTypeCategoryManagerInterface::FALLBACK_CATEGORY]['libraries'][] = 'link/drupal.link-icon';
+}

core/modules/link/migrations/state/link.migrate_drupal.yml

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+finished:
+  6:
+    link: link
+  7:
+    link: link

core/modules/link/src/LinkItemInterface.php

@@ -0,0 +1,54 @@
+<?php
+
+namespace Drupal\link;
+
+use Drupal\Core\Field\FieldItemInterface;
+
+/**
+ * Defines an interface for the link field item.
+ */
+interface LinkItemInterface extends FieldItemInterface {
+
+  /**
+   * Specifies whether the field supports only internal URLs.
+   */
+  const LINK_INTERNAL = 0x01;
+
+  /**
+   * Specifies whether the field supports only external URLs.
+   */
+  const LINK_EXTERNAL = 0x10;
+
+  /**
+   * Specifies whether the field supports both internal and external URLs.
+   */
+  const LINK_GENERIC = 0x11;
+
+  /**
+   * Determines if a link is external.
+   *
+   * @return bool
+   *   TRUE if the link is external, FALSE otherwise.
+   */
+  public function isExternal();
+
+  /**
+   * Gets the URL object.
+   *
+   * @return \Drupal\Core\Url
+   *   Returns a Url object.
+   *
+   * @throws \InvalidArgumentException
+   *   Thrown when there is a problem with field data.
+   */
+  public function getUrl();
+
+  /**
+   * Gets the link title.
+   *
+   * @return string|null
+   *   Returns the link title.
+   */
+  public function getTitle(): ?string;
+
+}

core/modules/link/src/Plugin/Field/FieldFormatter/LinkFormatter.php

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+<?php
+
+namespace Drupal\link\Plugin\Field\FieldFormatter;
+
+use Drupal\Component\Utility\Unicode;
+use Drupal\Core\Field\Attribute\FieldFormatter;
+use Drupal\Core\Field\FieldDefinitionInterface;
+use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Field\FormatterBase;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Path\PathValidatorInterface;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
+use Drupal\Core\Url;
+use Drupal\link\LinkItemInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Plugin implementation of the 'link' formatter.
+ */
+#[FieldFormatter(
+  id: 'link',
+  label: new TranslatableMarkup('Link'),
+  field_types: [
+    'link',
+  ],
+)]
+class LinkFormatter extends FormatterBase {
+
+  /**
+   * The path validator service.
+   *
+   * @var \Drupal\Core\Path\PathValidatorInterface
+   */
+  protected $pathValidator;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
+    return new static(
+      $plugin_id,
+      $plugin_definition,
+      $configuration['field_definition'],
+      $configuration['settings'],
+      $configuration['label'],
+      $configuration['view_mode'],
+      $configuration['third_party_settings'],
+      $container->get('path.validator')
+    );
+  }
+
+  /**
+   * Constructs a new LinkFormatter.
+   *
+   * @param string $plugin_id
+   *   The plugin_id for the formatter.
+   * @param mixed $plugin_definition
+   *   The plugin implementation definition.
+   * @param \Drupal\Core\Field\FieldDefinitionInterface $field_definition
+   *   The definition of the field to which the formatter is associated.
+   * @param array $settings
+   *   The formatter settings.
+   * @param string $label
+   *   The formatter label display setting.
+   * @param string $view_mode
+   *   The view mode.
+   * @param array $third_party_settings
+   *   Third party settings.
+   * @param \Drupal\Core\Path\PathValidatorInterface $path_validator
+   *   The path validator service.
+   */
+  public function __construct($plugin_id, $plugin_definition, FieldDefinitionInterface $field_definition, array $settings, $label, $view_mode, array $third_party_settings, PathValidatorInterface $path_validator) {
+    parent::__construct($plugin_id, $plugin_definition, $field_definition, $settings, $label, $view_mode, $third_party_settings);
+    $this->pathValidator = $path_validator;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function defaultSettings() {
+    return [
+      'trim_length' => '80',
+      'url_only' => '',
+      'url_plain' => '',
+      'rel' => '',
+      'target' => '',
+    ] + parent::defaultSettings();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function settingsForm(array $form, FormStateInterface $form_state) {
+    $elements = parent::settingsForm($form, $form_state);
+
+    $elements['trim_length'] = [
+      '#type' => 'number',
+      '#title' => $this->t('Trim link text length'),
+      '#field_suffix' => $this->t('characters'),
+      '#default_value' => $this->getSetting('trim_length'),
+      '#min' => 1,
+      '#description' => $this->t('Leave blank to allow unlimited link text lengths.'),
+    ];
+    $elements['url_only'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('URL only'),
+      '#default_value' => $this->getSetting('url_only'),
+      '#access' => $this->getPluginId() == 'link',
+    ];
+    $elements['url_plain'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('Show URL as plain text'),
+      '#default_value' => $this->getSetting('url_plain'),
+      '#access' => $this->getPluginId() == 'link',
+      '#states' => [
+        'visible' => [
+          ':input[name*="url_only"]' => ['checked' => TRUE],
+        ],
+      ],
+    ];
+    $elements['rel'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('Add rel="nofollow" to links'),
+      '#return_value' => 'nofollow',
+      '#default_value' => $this->getSetting('rel'),
+    ];
+    $elements['target'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('Open link in new window'),
+      '#return_value' => '_blank',
+      '#default_value' => $this->getSetting('target'),
+    ];
+
+    return $elements;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function settingsSummary() {
+    $summary = [];
+
+    $settings = $this->getSettings();
+
+    if (!empty($settings['trim_length'])) {
+      $summary[] = $this->t('Link text trimmed to @limit characters', ['@limit' => $settings['trim_length']]);
+    }
+    else {
+      $summary[] = $this->t('Link text not trimmed');
+    }
+    if ($this->getPluginId() == 'link' && !empty($settings['url_only'])) {
+      if (!empty($settings['url_plain'])) {
+        $summary[] = $this->t('Show URL only as plain-text');
+      }
+      else {
+        $summary[] = $this->t('Show URL only');
+      }
+    }
+    if (!empty($settings['rel'])) {
+      $summary[] = $this->t('Add rel="@rel"', ['@rel' => $settings['rel']]);
+    }
+    if (!empty($settings['target'])) {
+      $summary[] = $this->t('Open link in new window');
+    }
+
+    return $summary;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function viewElements(FieldItemListInterface $items, $langcode) {
+    $element = [];
+    $entity = $items->getEntity();
+    $settings = $this->getSettings();
+
+    foreach ($items as $delta => $item) {
+      // By default use the full URL as the link text.
+      $url = $this->buildUrl($item);
+      $link_title = $url->toString();
+
+      // If the title field value is available, use it for the link text.
+      if (empty($settings['url_only']) && !empty($item->title)) {
+        // Unsanitized token replacement here because the entire link title
+        // gets auto-escaped during link generation in
+        // \Drupal\Core\Utility\LinkGenerator::generate().
+        $link_title = \Drupal::token()->replace($item->title, [$entity->getEntityTypeId() => $entity], ['clear' => TRUE]);
+      }
+
+      // Trim the link text to the desired length.
+      if (!empty($settings['trim_length'])) {
+        $link_title = Unicode::truncate($link_title, $settings['trim_length'], FALSE, TRUE);
+      }
+
+      if (!empty($settings['url_only']) && !empty($settings['url_plain'])) {
+        $element[$delta] = [
+          '#plain_text' => $link_title,
+        ];
+
+        if (!empty($item->_attributes)) {
+          // Piggyback on the metadata attributes, which will be placed in the
+          // field template wrapper, and set the URL value in a content
+          // attribute.
+          $content = str_replace('internal:/', '', $item->uri);
+          $item->_attributes += ['content' => $content];
+        }
+      }
+      else {
+        // Skip the #options to prevent duplications of query parameters.
+        $element[$delta] = [
+          '#type' => 'link',
+          '#title' => $link_title,
+          '#url' => $url,
+        ];
+
+        if (!empty($item->_attributes)) {
+          $element[$delta]['#attributes'] = $item->_attributes;
+          // Unset field item attributes since they have been included in the
+          // formatter output and should not be rendered in the field template.
+          unset($item->_attributes);
+        }
+      }
+    }
+
+    return $element;
+  }
+
+  /**
+   * Builds the \Drupal\Core\Url object for a link field item.
+   *
+   * @param \Drupal\link\LinkItemInterface $item
+   *   The link field item being rendered.
+   *
+   * @return \Drupal\Core\Url
+   *   A Url object.
+   */
+  protected function buildUrl(LinkItemInterface $item) {
+    try {
+      $url = $item->getUrl();
+    }
+    catch (\InvalidArgumentException $e) {
+      // @todo Add logging here in https://www.drupal.org/project/drupal/issues/3348020
+      $url = Url::fromRoute('<none>');
+    }
+
+    $settings = $this->getSettings();
+    $options = $item->options;
+    $options += $url->getOptions();
+
+    // Add optional 'rel' attribute to link options.
+    if (!empty($settings['rel'])) {
+      $options['attributes']['rel'] = $settings['rel'];
+    }
+    // Add optional 'target' attribute to link options.
+    if (!empty($settings['target'])) {
+      $options['attributes']['target'] = $settings['target'];
+    }
+    $url->setOptions($options);
+
+    return $url;
+  }
+
+}

core/modules/link/src/Plugin/Field/FieldFormatter/LinkSeparateFormatter.php

@@ -0,0 +1,90 @@
+<?php
+
+namespace Drupal\link\Plugin\Field\FieldFormatter;
+
+use Drupal\Component\Utility\Unicode;
+use Drupal\Core\Field\Attribute\FieldFormatter;
+use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
+
+/**
+ * Plugin implementation of the 'link_separate' formatter.
+ *
+ * @todo https://www.drupal.org/node/1829202 Merge into 'link' formatter once
+ *   there is a #type like 'item' that can render a compound label and content
+ *   outside of a form context.
+ */
+#[FieldFormatter(
+  id: 'link_separate',
+  label: new TranslatableMarkup('Separate link text and URL'),
+  field_types: [
+    'link',
+  ],
+)]
+class LinkSeparateFormatter extends LinkFormatter {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function defaultSettings() {
+    return [
+      'trim_length' => 80,
+      'rel' => '',
+      'target' => '',
+    ] + parent::defaultSettings();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function viewElements(FieldItemListInterface $items, $langcode) {
+    $element = [];
+    $entity = $items->getEntity();
+    $settings = $this->getSettings();
+
+    foreach ($items as $delta => $item) {
+      // By default use the full URL as the link text.
+      $url = $this->buildUrl($item);
+      $link_title = $url->toString();
+
+      // If the link text field value is available, use it for the text.
+      if (empty($settings['url_only']) && !empty($item->title)) {
+        // Unsanitized token replacement here because the entire link title
+        // gets auto-escaped during link generation in
+        // \Drupal\Core\Utility\LinkGenerator::generate().
+        $link_title = \Drupal::token()->replace($item->title, [$entity->getEntityTypeId() => $entity], ['clear' => TRUE]);
+      }
+
+      // The link_separate formatter has two titles; the link text (as in the
+      // field values) and the URL itself. If there is no link text value,
+      // $link_title defaults to the URL, so it needs to be unset.
+      // The URL version may need to be trimmed as well.
+      if (empty($item->title)) {
+        $link_title = NULL;
+      }
+      $url_title = $url->toString();
+      if (!empty($settings['trim_length'])) {
+        $link_title = $link_title !== NULL ? Unicode::truncate($link_title, $settings['trim_length'], FALSE, TRUE) : NULL;
+        $url_title = Unicode::truncate($url_title, $settings['trim_length'], FALSE, TRUE);
+      }
+
+      $element[$delta] = [
+        '#theme' => 'link_formatter_link_separate',
+        '#title' => $link_title,
+        '#url_title' => $url_title,
+        '#url' => $url,
+      ];
+
+      if (!empty($item->_attributes)) {
+        // Set our attributes on the <a> element that is being built.
+        $url->setOption('attributes', $item->_attributes);
+
+        // Unset field item attributes since they have been included in the
+        // formatter output and should not be rendered in the field template.
+        unset($item->_attributes);
+      }
+    }
+    return $element;
+  }
+
+}

core/modules/link/src/Plugin/Field/FieldType/LinkItem.php

@@ -0,0 +1,207 @@
+<?php
+
+namespace Drupal\link\Plugin\Field\FieldType;
+
+use Drupal\Component\Utility\Random;
+use Drupal\Core\Field\Attribute\FieldType;
+use Drupal\Core\Field\FieldDefinitionInterface;
+use Drupal\Core\Field\FieldItemBase;
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
+use Drupal\Core\TypedData\DataDefinition;
+use Drupal\Core\TypedData\MapDataDefinition;
+use Drupal\Core\Url;
+use Drupal\link\LinkItemInterface;
+
+/**
+ * Plugin implementation of the 'link' field type.
+ */
+#[FieldType(
+  id: "link",
+  label: new TranslatableMarkup("Link"),
+  description: new TranslatableMarkup("Stores a URL string, optional varchar link text, and optional blob of attributes to assemble a link."),
+  default_widget: "link_default",
+  default_formatter: "link",
+  constraints: [
+    "LinkType" => [],
+    "LinkAccess" => [],
+    "LinkExternalProtocols" => [],
+    "LinkNotExistingInternal" => [],
+  ]
+)]
+class LinkItem extends FieldItemBase implements LinkItemInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function defaultFieldSettings() {
+    return [
+      'title' => DRUPAL_OPTIONAL,
+      'link_type' => LinkItemInterface::LINK_GENERIC,
+    ] + parent::defaultFieldSettings();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function propertyDefinitions(FieldStorageDefinitionInterface $field_definition) {
+    $properties['uri'] = DataDefinition::create('uri')
+      ->setLabel(new TranslatableMarkup('URI'));
+
+    $properties['title'] = DataDefinition::create('string')
+      ->setLabel(new TranslatableMarkup('Link text'));
+
+    $properties['options'] = MapDataDefinition::create()
+      ->setLabel(new TranslatableMarkup('Options'));
+
+    return $properties;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function schema(FieldStorageDefinitionInterface $field_definition) {
+    return [
+      'columns' => [
+        'uri' => [
+          'description' => 'The URI of the link.',
+          'type' => 'varchar',
+          'length' => 2048,
+        ],
+        'title' => [
+          'description' => 'The link text.',
+          'type' => 'varchar',
+          'length' => 255,
+        ],
+        'options' => [
+          'description' => 'Serialized array of options for the link.',
+          'type' => 'blob',
+          'size' => 'big',
+          'serialize' => TRUE,
+        ],
+      ],
+      'indexes' => [
+        'uri' => [['uri', 30]],
+      ],
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function fieldSettingsForm(array $form, FormStateInterface $form_state) {
+    $element = [];
+
+    $element['link_type'] = [
+      '#type' => 'radios',
+      '#title' => $this->t('Allowed link type'),
+      '#default_value' => $this->getSetting('link_type'),
+      '#options' => [
+        static::LINK_INTERNAL => $this->t('Internal links only'),
+        static::LINK_EXTERNAL => $this->t('External links only'),
+        static::LINK_GENERIC => $this->t('Both internal and external links'),
+      ],
+    ];
+
+    $element['title'] = [
+      '#type' => 'radios',
+      '#title' => $this->t('Allow link text'),
+      '#default_value' => $this->getSetting('title'),
+      '#options' => [
+        DRUPAL_DISABLED => $this->t('Disabled'),
+        DRUPAL_OPTIONAL => $this->t('Optional'),
+        DRUPAL_REQUIRED => $this->t('Required'),
+      ],
+    ];
+
+    return $element;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function generateSampleValue(FieldDefinitionInterface $field_definition) {
+    $random = new Random();
+    if ($field_definition->getItemDefinition()->getSetting('link_type') & LinkItemInterface::LINK_EXTERNAL) {
+      // Set of possible top-level domains.
+      $tlds = ['com', 'net', 'gov', 'org', 'edu', 'biz', 'info'];
+      // Set random length for the domain name.
+      $domain_length = mt_rand(7, 15);
+
+      switch ($field_definition->getSetting('title')) {
+        case DRUPAL_DISABLED:
+          $values['title'] = '';
+          break;
+
+        case DRUPAL_REQUIRED:
+          $values['title'] = $random->sentences(4);
+          break;
+
+        case DRUPAL_OPTIONAL:
+          // In case of optional title, randomize its generation.
+          $values['title'] = mt_rand(0, 1) ? $random->sentences(4) : '';
+          break;
+      }
+      $values['uri'] = 'https://www.' . $random->word($domain_length) . '.' . $tlds[mt_rand(0, (count($tlds) - 1))];
+    }
+    else {
+      $values['uri'] = 'base:' . $random->name(mt_rand(1, 64));
+    }
+    return $values;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function isEmpty() {
+    $value = $this->get('uri')->getValue();
+    return $value === NULL || $value === '';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function isExternal() {
+    return $this->getUrl()->isExternal();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function mainPropertyName() {
+    return 'uri';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getUrl() {
+    return Url::fromUri($this->uri, (array) $this->options);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getTitle(): ?string {
+    return $this->title ?: NULL;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setValue($values, $notify = TRUE) {
+    // Treat the values as property value of the main property, if no array is
+    // given.
+    if (isset($values) && !is_array($values)) {
+      $values = [static::mainPropertyName() => $values];
+    }
+    if (isset($values)) {
+      $values += [
+        'options' => [],
+      ];
+    }
+    parent::setValue($values, $notify);
+  }
+
+}

core/modules/link/src/Plugin/Field/FieldWidget/LinkWidget.php

@@ -0,0 +1,462 @@
+<?php
+
+namespace Drupal\link\Plugin\Field\FieldWidget;
+
+use Drupal\Core\Field\Attribute\FieldWidget;
+use Drupal\Core\StringTranslation\TranslatableMarkup;
+use Drupal\Core\Url;
+use Drupal\Core\Entity\Element\EntityAutocomplete;
+use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Field\WidgetBase;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\link\LinkItemInterface;
+use Symfony\Component\Validator\ConstraintViolation;
+use Symfony\Component\Validator\ConstraintViolationListInterface;
+
+/**
+ * Plugin implementation of the 'link' widget.
+ */
+#[FieldWidget(
+  id: 'link_default',
+  label: new TranslatableMarkup('Link'),
+  field_types: ['link'],
+)]
+class LinkWidget extends WidgetBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function defaultSettings() {
+    return [
+      'placeholder_url' => '',
+      'placeholder_title' => '',
+    ] + parent::defaultSettings();
+  }
+
+  /**
+   * Gets the URI without the 'internal:' or 'entity:' scheme.
+   *
+   * The following two forms of URIs are transformed:
+   * - 'entity:' URIs: to entity autocomplete ("label (entity id)") strings;
+   * - 'internal:' URIs: the scheme is stripped.
+   *
+   * This method is the inverse of ::getUserEnteredStringAsUri().
+   *
+   * @param string $uri
+   *   The URI to get the displayable string for.
+   *
+   * @return string
+   *
+   * @see static::getUserEnteredStringAsUri()
+   */
+  protected static function getUriAsDisplayableString($uri) {
+    $scheme = parse_url($uri, PHP_URL_SCHEME);
+
+    // By default, the displayable string is the URI.
+    $displayable_string = $uri;
+
+    // A different displayable string may be chosen in case of the 'internal:'
+    // or 'entity:' built-in schemes.
+    if ($scheme === 'internal') {
+      $uri_reference = explode(':', $uri, 2)[1];
+
+      // @todo '<front>' is valid input for BC reasons, may be removed by
+      //   https://www.drupal.org/node/2421941
+      $path = parse_url($uri, PHP_URL_PATH);
+      if ($path === '/') {
+        $uri_reference = '<front>' . substr($uri_reference, 1);
+      }
+
+      $displayable_string = $uri_reference;
+    }
+    elseif ($scheme === 'entity') {
+      [$entity_type, $entity_id] = explode('/', substr($uri, 7), 2);
+      // Show the 'entity:' URI as the entity autocomplete would.
+      // @todo Support entity types other than 'node'. Will be fixed in
+      //   https://www.drupal.org/node/2423093.
+      if ($entity_type == 'node' && $entity = \Drupal::entityTypeManager()->getStorage($entity_type)->load($entity_id)) {
+        $displayable_string = EntityAutocomplete::getEntityLabels([$entity]);
+      }
+    }
+    elseif ($scheme === 'route') {
+      $displayable_string = ltrim($displayable_string, 'route:');
+    }
+
+    return $displayable_string;
+  }
+
+  /**
+   * Gets the user-entered string as a URI.
+   *
+   * The following two forms of input are mapped to URIs:
+   * - entity autocomplete ("label (entity id)") strings: to 'entity:' URIs;
+   * - strings without a detectable scheme: to 'internal:' URIs.
+   *
+   * This method is the inverse of ::getUriAsDisplayableString().
+   *
+   * @param string $string
+   *   The user-entered string.
+   *
+   * @return string
+   *   The URI, if a non-empty $uri was passed.
+   *
+   * @see static::getUriAsDisplayableString()
+   */
+  protected static function getUserEnteredStringAsUri($string) {
+    // By default, assume the entered string is a URI.
+    $uri = trim($string);
+
+    // Detect entity autocomplete string, map to 'entity:' URI.
+    $entity_id = EntityAutocomplete::extractEntityIdFromAutocompleteInput($string);
+    if ($entity_id !== NULL) {
+      // @todo Support entity types other than 'node'. Will be fixed in
+      //   https://www.drupal.org/node/2423093.
+      $uri = 'entity:node/' . $entity_id;
+    }
+    // Support linking to nothing.
+    elseif (in_array($string, ['<nolink>', '<none>', '<button>'], TRUE)) {
+      $uri = 'route:' . $string;
+    }
+    // Detect a schemeless string, map to 'internal:' URI.
+    elseif (!empty($string) && parse_url($string, PHP_URL_SCHEME) === NULL) {
+      // @todo '<front>' is valid input for BC reasons, may be removed by
+      //   https://www.drupal.org/node/2421941
+      // - '<front>' -> '/'
+      // - '<front>#foo' -> '/#foo'
+      if (str_starts_with($string, '<front>')) {
+        $string = '/' . substr($string, strlen('<front>'));
+      }
+      $uri = 'internal:' . $string;
+    }
+
+    return $uri;
+  }
+
+  /**
+   * Form element validation handler for the 'uri' element.
+   *
+   * Disallows saving inaccessible or untrusted URLs.
+   */
+  public static function validateUriElement($element, FormStateInterface $form_state, $form) {
+    $uri = static::getUserEnteredStringAsUri($element['#value']);
+    $form_state->setValueForElement($element, $uri);
+
+    // If getUserEnteredStringAsUri() mapped the entered value to an 'internal:'
+    // URI , ensure the raw value begins with '/', '?' or '#'.
+    // @todo '<front>' is valid input for BC reasons, may be removed by
+    //   https://www.drupal.org/node/2421941
+    if (parse_url($uri, PHP_URL_SCHEME) === 'internal' && !in_array($element['#value'][0], ['/', '?', '#'], TRUE) && !str_starts_with($element['#value'], '<front>')) {
+      $form_state->setError($element, new TranslatableMarkup('Manually entered paths should start with one of the following characters: / ? #'));
+      return;
+    }
+  }
+
+  /**
+   * Form element validation handler for the 'title' element.
+   *
+   * Conditionally requires the link title if a URL value was filled in.
+   */
+  public static function validateTitleElement(&$element, FormStateInterface $form_state, $form) {
+    if ($element['uri']['#value'] !== '' && $element['title']['#value'] === '') {
+      // We expect the field name placeholder value to be wrapped in $this->t() here,
+      // so it won't be escaped again as it's already marked safe.
+      $form_state->setError($element['title'], new TranslatableMarkup('@title field is required if there is @uri input.', ['@title' => $element['title']['#title'], '@uri' => $element['uri']['#title']]));
+    }
+  }
+
+  /**
+   * Form element validation handler for the 'title' element.
+   *
+   * Requires the URL value if a link title was filled in.
+   */
+  public static function validateTitleNoLink(&$element, FormStateInterface $form_state, $form) {
+    if ($element['uri']['#value'] === '' && $element['title']['#value'] !== '') {
+      $form_state->setError($element['uri'], new TranslatableMarkup('The @uri field is required when the @title field is specified.', ['@title' => $element['title']['#title'], '@uri' => $element['uri']['#title']]));
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {
+    /** @var \Drupal\link\LinkItemInterface $item */
+    $item = $items[$delta];
+
+    $display_uri = NULL;
+    if (!$item->isEmpty()) {
+      try {
+        // The current field value could have been entered by a different user.
+        // However, if it is inaccessible to the current user, do not display it
+        // to them.
+        if (\Drupal::currentUser()->hasPermission('link to any page') || $item->getUrl()->access()) {
+          $display_uri = static::getUriAsDisplayableString($item->uri);
+        }
+      }
+      catch (\InvalidArgumentException $e) {
+        // If $item->uri is invalid, show value as is, so the user can see what
+        // to edit.
+        // @todo Add logging here in https://www.drupal.org/project/drupal/issues/3348020
+        $display_uri = $item->uri;
+      }
+    }
+    $element['uri'] = [
+      '#type' => 'url',
+      '#title' => $this->t('URL'),
+      '#placeholder' => $this->getSetting('placeholder_url'),
+      '#default_value' => $display_uri,
+      '#element_validate' => [[static::class, 'validateUriElement']],
+      '#maxlength' => 2048,
+      '#required' => $element['#required'],
+      '#link_type' => $this->getFieldSetting('link_type'),
+    ];
+
+    // If the field is configured to support internal links, it cannot use the
+    // 'url' form element and we have to do the validation ourselves.
+    if ($this->supportsInternalLinks()) {
+      $element['uri']['#type'] = 'entity_autocomplete';
+      // @todo The user should be able to select an entity type. Will be fixed
+      //   in https://www.drupal.org/node/2423093.
+      $element['uri']['#target_type'] = 'node';
+      // Disable autocompletion when the first character is '/', '#' or '?'.
+      $element['uri']['#attributes']['data-autocomplete-first-character-blacklist'] = '/#?';
+
+      // The link widget is doing its own processing in
+      // static::getUriAsDisplayableString().
+      $element['uri']['#process_default_value'] = FALSE;
+    }
+
+    // If the field is configured to allow only internal links, add a useful
+    // element prefix and description.
+    if (!$this->supportsExternalLinks()) {
+      $element['uri']['#field_prefix'] = rtrim(Url::fromRoute('<front>', [], ['absolute' => TRUE])->toString(), '/');
+      $element['uri']['#description'] = $this->t('This must be an internal path such as %add-node. You can also start typing the title of a piece of content to select it. Enter %front to link to the front page. Enter %nolink to display link text only. Enter %button to display keyboard-accessible link text only.', ['%add-node' => '/node/add', '%front' => '<front>', '%nolink' => '<nolink>', '%button' => '<button>']);
+    }
+    // If the field is configured to allow both internal and external links,
+    // show a useful description.
+    elseif ($this->supportsExternalLinks() && $this->supportsInternalLinks()) {
+      $element['uri']['#description'] = $this->t('Start typing the title of a piece of content to select it. You can also enter an internal path such as %add-node or an external URL such as %url. Enter %front to link to the front page. Enter %nolink to display link text only. Enter %button to display keyboard-accessible link text only.', ['%front' => '<front>', '%add-node' => '/node/add', '%url' => 'https://example.com', '%nolink' => '<nolink>', '%button' => '<button>']);
+    }
+    // If the field is configured to allow only external links, show a useful
+    // description.
+    elseif ($this->supportsExternalLinks() && !$this->supportsInternalLinks()) {
+      $element['uri']['#description'] = $this->t('This must be an external URL such as %url.', ['%url' => 'https://example.com']);
+    }
+
+    // Make uri required on the front-end when title filled-in.
+    if (!$this->isDefaultValueWidget($form_state) && $this->getFieldSetting('title') !== DRUPAL_DISABLED && !$element['uri']['#required']) {
+      $parents = $element['#field_parents'];
+      $parents[] = $this->fieldDefinition->getName();
+      $selector = $root = array_shift($parents);
+      if ($parents) {
+        $selector = $root . '[' . implode('][', $parents) . ']';
+      }
+
+      $element['uri']['#states']['required'] = [
+        ':input[name="' . $selector . '[' . $delta . '][title]"]' => ['filled' => TRUE],
+      ];
+    }
+
+    $element['title'] = [
+      '#type' => 'textfield',
+      '#title' => $this->t('Link text'),
+      '#placeholder' => $this->getSetting('placeholder_title'),
+      '#default_value' => $items[$delta]->title ?? NULL,
+      '#maxlength' => 255,
+      '#access' => $this->getFieldSetting('title') != DRUPAL_DISABLED,
+      '#required' => $this->getFieldSetting('title') === DRUPAL_REQUIRED && $element['#required'],
+    ];
+    // Post-process the title field to make it conditionally required if URL is
+    // non-empty. Omit the validation on the field edit form, since the field
+    // settings cannot be saved otherwise.
+    //
+    // Validate that title field is filled out (regardless of uri) when it is a
+    // required field.
+    if (!$this->isDefaultValueWidget($form_state) && $this->getFieldSetting('title') === DRUPAL_REQUIRED) {
+      $element['#element_validate'][] = [static::class, 'validateTitleElement'];
+      $element['#element_validate'][] = [static::class, 'validateTitleNoLink'];
+
+      if (!$element['title']['#required']) {
+        // Make title required on the front-end when URI filled-in.
+
+        $parents = $element['#field_parents'];
+        $parents[] = $this->fieldDefinition->getName();
+        $selector = $root = array_shift($parents);
+        if ($parents) {
+          $selector = $root . '[' . implode('][', $parents) . ']';
+        }
+
+        $element['title']['#states']['required'] = [
+          ':input[name="' . $selector . '[' . $delta . '][uri]"]' => ['filled' => TRUE],
+        ];
+      }
+    }
+
+    // Ensure that a URI is always entered when an optional title field is
+    // submitted.
+    if (!$this->isDefaultValueWidget($form_state) && $this->getFieldSetting('title') == DRUPAL_OPTIONAL) {
+      $element['#element_validate'][] = [static::class, 'validateTitleNoLink'];
+    }
+
+    // Exposing the attributes array in the widget is left for alternate and more
+    // advanced field widgets.
+    $element['attributes'] = [
+      '#type' => 'value',
+      '#tree' => TRUE,
+      '#value' => !empty($items[$delta]->options['attributes']) ? $items[$delta]->options['attributes'] : [],
+      '#attributes' => ['class' => ['link-field-widget-attributes']],
+    ];
+
+    // If cardinality is 1, ensure a proper label is output for the field.
+    if ($this->fieldDefinition->getFieldStorageDefinition()->getCardinality() == 1) {
+      // If the link title is disabled, use the field definition label as the
+      // title of the 'uri' element.
+      if ($this->getFieldSetting('title') == DRUPAL_DISABLED) {
+        $element['uri']['#title'] = $element['#title'];
+        // By default the field description is added to the title field. Since
+        // the title field is disabled, we add the description, if given, to the
+        // uri element instead.
+        if (!empty($element['#description'])) {
+          if (empty($element['uri']['#description'])) {
+            $element['uri']['#description'] = $element['#description'];
+          }
+          else {
+            // If we have the description of the type of field together with
+            // the user provided description, we want to make a distinction
+            // between "core help text" and "user entered help text". To make
+            // this distinction more clear, we put them in an unordered list.
+            $element['uri']['#description'] = [
+              '#theme' => 'item_list',
+              '#items' => [
+                // Assume the user-specified description has the most relevance,
+                // so place it first.
+                $element['#description'],
+                $element['uri']['#description'],
+              ],
+            ];
+          }
+        }
+      }
+      // Otherwise wrap everything in a details element.
+      else {
+        $element += [
+          '#type' => 'fieldset',
+        ];
+      }
+    }
+
+    return $element;
+  }
+
+  /**
+   * Indicates enabled support for link to routes.
+   *
+   * @return bool
+   *   Returns TRUE if the LinkItem field is configured to support links to
+   *   routes, otherwise FALSE.
+   */
+  protected function supportsInternalLinks() {
+    $link_type = $this->getFieldSetting('link_type');
+    return (bool) ($link_type & LinkItemInterface::LINK_INTERNAL);
+  }
+
+  /**
+   * Indicates enabled support for link to external URLs.
+   *
+   * @return bool
+   *   Returns TRUE if the LinkItem field is configured to support links to
+   *   external URLs, otherwise FALSE.
+   */
+  protected function supportsExternalLinks() {
+    $link_type = $this->getFieldSetting('link_type');
+    return (bool) ($link_type & LinkItemInterface::LINK_EXTERNAL);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function settingsForm(array $form, FormStateInterface $form_state) {
+    $elements = parent::settingsForm($form, $form_state);
+
+    $elements['placeholder_url'] = [
+      '#type' => 'textfield',
+      '#title' => $this->t('Placeholder for URL'),
+      '#default_value' => $this->getSetting('placeholder_url'),
+      '#description' => $this->t('Text that will be shown inside the field until a value is entered. This hint is usually a sample value or a brief description of the expected format.'),
+    ];
+    $elements['placeholder_title'] = [
+      '#type' => 'textfield',
+      '#title' => $this->t('Placeholder for link text'),
+      '#default_value' => $this->getSetting('placeholder_title'),
+      '#description' => $this->t('Text that will be shown inside the field until a value is entered. This hint is usually a sample value or a brief description of the expected format.'),
+      '#states' => [
+        'invisible' => [
+          ':input[name="instance[settings][title]"]' => ['value' => DRUPAL_DISABLED],
+        ],
+      ],
+    ];
+
+    return $elements;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function settingsSummary() {
+    $summary = [];
+
+    $placeholder_title = $this->getSetting('placeholder_title');
+    $placeholder_url = $this->getSetting('placeholder_url');
+    if (empty($placeholder_title) && empty($placeholder_url)) {
+      $summary[] = $this->t('No placeholders');
+    }
+    else {
+      if (!empty($placeholder_title)) {
+        $summary[] = $this->t('Title placeholder: @placeholder_title', ['@placeholder_title' => $placeholder_title]);
+      }
+      if (!empty($placeholder_url)) {
+        $summary[] = $this->t('URL placeholder: @placeholder_url', ['@placeholder_url' => $placeholder_url]);
+      }
+    }
+
+    return $summary;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function massageFormValues(array $values, array $form, FormStateInterface $form_state) {
+    foreach ($values as &$value) {
+      $value['uri'] = static::getUserEnteredStringAsUri($value['uri']);
+      $value += ['options' => []];
+    }
+    return $values;
+  }
+
+  /**
+   * {@inheritdoc}
+   *
+   * Override the '%uri' message parameter, to ensure that 'internal:' URIs
+   * show a validation error message that doesn't mention that scheme.
+   */
+  public function flagErrors(FieldItemListInterface $items, ConstraintViolationListInterface $violations, array $form, FormStateInterface $form_state) {
+    /** @var \Symfony\Component\Validator\ConstraintViolationInterface $violation */
+    foreach ($violations as $offset => $violation) {
+      $parameters = $violation->getParameters();
+      if (isset($parameters['@uri'])) {
+        $parameters['@uri'] = static::getUriAsDisplayableString($parameters['@uri']);
+        $violations->set($offset, new ConstraintViolation(
+          $this->t($violation->getMessageTemplate(), $parameters),
+          $violation->getMessageTemplate(),
+          $parameters,
+          $violation->getRoot(),
+          $violation->getPropertyPath(),
+          $violation->getInvalidValue(),
+          $violation->getPlural(),
+          $violation->getCode()
+        ));
+      }
+    }
+    parent::flagErrors($items, $violations, $form, $form_state);
+  }
+
+}

core/modules/link/src/Plugin/Validation/Constraint/LinkAccessConstraint.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace Drupal\link\Plugin\Validation\Constraint;
+
+use Drupal\Core\StringTranslation\TranslatableMarkup;
+use Drupal\Core\Validation\Attribute\Constraint;
+use Symfony\Component\Validator\Constraint as SymfonyConstraint;
+
+/**
+ * Defines an access validation constraint for links.
+ */
+#[Constraint(
+  id: 'LinkAccess',
+  label: new TranslatableMarkup('Link URI can be accessed by the user.', [], ['context' => 'Validation'])
+)]
+class LinkAccessConstraint extends SymfonyConstraint {
+
+  public $message = "The path '@uri' is inaccessible.";
+
+}

core/modules/link/src/Plugin/Validation/Constraint/LinkAccessConstraintValidator.php

@@ -0,0 +1,67 @@
+<?php
+
+namespace Drupal\link\Plugin\Validation\Constraint;
+
+use Drupal\Core\Session\AccountProxyInterface;
+use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\ConstraintValidator;
+
+/**
+ * Validates the LinkAccess constraint.
+ */
+class LinkAccessConstraintValidator extends ConstraintValidator implements ContainerInjectionInterface {
+
+  /**
+   * Proxy for the current user account.
+   *
+   * @var \Drupal\Core\Session\AccountProxyInterface
+   */
+  // phpcs:ignore Drupal.NamingConventions.ValidVariableName.LowerCamelName
+  protected $current_user;
+
+  /**
+   * Constructs an instance of the LinkAccessConstraintValidator class.
+   *
+   * @param \Drupal\Core\Session\AccountProxyInterface $current_user
+   *   The current user account.
+   */
+  public function __construct(AccountProxyInterface $current_user) {
+    $this->current_user = $current_user;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container) {
+    return new static(
+      $container->get('current_user')
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   *
+   * phpcs:ignore Drupal.Commenting.FunctionComment.VoidReturn
+   * @return void
+   */
+  public function validate($value, Constraint $constraint) {
+    if (isset($value)) {
+      try {
+        $url = $value->getUrl();
+      }
+      // If the URL is malformed this constraint cannot check access.
+      catch (\InvalidArgumentException $e) {
+        return;
+      }
+      // Disallow URLs if the current user doesn't have the 'link to any page'
+      // permission nor can access this URI.
+      $allowed = $this->current_user->hasPermission('link to any page') || $url->access();
+      if (!$allowed) {
+        $this->context->addViolation($constraint->message, ['@uri' => $value->uri]);
+      }
+    }
+  }
+
+}

core/modules/link/src/Plugin/Validation/Constraint/LinkExternalProtocolsConstraint.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace Drupal\link\Plugin\Validation\Constraint;
+
+use Drupal\Core\StringTranslation\TranslatableMarkup;
+use Drupal\Core\Validation\Attribute\Constraint;
+use Symfony\Component\Validator\Constraint as SymfonyConstraint;
+
+/**
+ * Defines a protocol validation constraint for links to external URLs.
+ */
+#[Constraint(
+  id: 'LinkExternalProtocols',
+  label: new TranslatableMarkup('No dangerous external protocols', [], ['context' => 'Validation'])
+)]
+class LinkExternalProtocolsConstraint extends SymfonyConstraint {
+
+  public $message = "The path '@uri' is invalid.";
+
+}

core/modules/link/src/Plugin/Validation/Constraint/LinkExternalProtocolsConstraintValidator.php

@@ -0,0 +1,37 @@
+<?php
+
+namespace Drupal\link\Plugin\Validation\Constraint;
+
+use Drupal\Component\Utility\UrlHelper;
+use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\ConstraintValidator;
+
+/**
+ * Validates the LinkExternalProtocols constraint.
+ */
+class LinkExternalProtocolsConstraintValidator extends ConstraintValidator {
+
+  /**
+   * {@inheritdoc}
+   *
+   * phpcs:ignore Drupal.Commenting.FunctionComment.VoidReturn
+   * @return void
+   */
+  public function validate($value, Constraint $constraint) {
+    if (isset($value)) {
+      try {
+        /** @var \Drupal\Core\Url $url */
+        $url = $value->getUrl();
+      }
+      // If the URL is malformed this constraint cannot check further.
+      catch (\InvalidArgumentException $e) {
+        return;
+      }
+      // Disallow external URLs using untrusted protocols.
+      if ($url->isExternal() && !in_array(parse_url($url->getUri(), PHP_URL_SCHEME), UrlHelper::getAllowedProtocols())) {
+        $this->context->addViolation($constraint->message, ['@uri' => $value->uri]);
+      }
+    }
+  }
+
+}

core/modules/link/src/Plugin/Validation/Constraint/LinkNotExistingInternalConstraint.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace Drupal\link\Plugin\Validation\Constraint;
+
+use Drupal\Core\StringTranslation\TranslatableMarkup;
+use Drupal\Core\Validation\Attribute\Constraint;
+use Symfony\Component\Validator\Constraint as SymfonyConstraint;
+
+/**
+ * Defines a protocol validation constraint for links to broken internal URLs.
+ */
+#[Constraint(
+  id: 'LinkNotExistingInternal',
+  label: new TranslatableMarkup('No broken internal links', [], ['context' => 'Validation'])
+)]
+class LinkNotExistingInternalConstraint extends SymfonyConstraint {
+
+  public $message = "The path '@uri' is invalid.";
+
+}

core/modules/link/src/Plugin/Validation/Constraint/LinkNotExistingInternalConstraintValidator.php

@@ -0,0 +1,56 @@
+<?php
+
+namespace Drupal\link\Plugin\Validation\Constraint;
+
+use Symfony\Component\Routing\Exception\InvalidParameterException;
+use Symfony\Component\Routing\Exception\MissingMandatoryParametersException;
+use Symfony\Component\Routing\Exception\RouteNotFoundException;
+use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\ConstraintValidator;
+
+/**
+ * Validates the LinkNotExistingInternal constraint.
+ */
+class LinkNotExistingInternalConstraintValidator extends ConstraintValidator {
+
+  /**
+   * {@inheritdoc}
+   *
+   * phpcs:ignore Drupal.Commenting.FunctionComment.VoidReturn
+   * @return void
+   */
+  public function validate($value, Constraint $constraint) {
+    if (isset($value)) {
+      try {
+        /** @var \Drupal\Core\Url $url */
+        $url = $value->getUrl();
+      }
+      // If the URL is malformed this constraint cannot check further.
+      catch (\InvalidArgumentException $e) {
+        return;
+      }
+
+      if ($url->isRouted()) {
+        $allowed = TRUE;
+        try {
+          $url->toString(TRUE);
+        }
+        // The following exceptions are all possible during URL generation, and
+        // should be considered as disallowed URLs.
+        catch (RouteNotFoundException $e) {
+          $allowed = FALSE;
+        }
+        catch (InvalidParameterException $e) {
+          $allowed = FALSE;
+        }
+        catch (MissingMandatoryParametersException $e) {
+          $allowed = FALSE;
+        }
+        if (!$allowed) {
+          $this->context->addViolation($constraint->message, ['@uri' => $value->uri]);
+        }
+      }
+    }
+  }
+
+}

core/modules/link/src/Plugin/Validation/Constraint/LinkTypeConstraint.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace Drupal\link\Plugin\Validation\Constraint;
+
+use Drupal\Core\StringTranslation\TranslatableMarkup;
+use Drupal\Core\Validation\Attribute\Constraint;
+use Symfony\Component\Validator\Constraint as SymfonyConstraint;
+
+/**
+ * Validation constraint for links receiving data allowed by its settings.
+ */
+#[Constraint(
+  id: 'LinkType',
+  label: new TranslatableMarkup('Link data valid for link type.', [], ['context' => 'Validation'])
+)]
+class LinkTypeConstraint extends SymfonyConstraint {
+
+  public $message = "The path '@uri' is invalid.";
+
+}

core/modules/link/src/Plugin/Validation/Constraint/LinkTypeConstraintValidator.php

@@ -0,0 +1,51 @@
+<?php
+
+namespace Drupal\link\Plugin\Validation\Constraint;
+
+use Drupal\link\LinkItemInterface;
+use Symfony\Component\Validator\Constraint;
+use Symfony\Component\Validator\ConstraintValidator;
+
+/**
+ * Constraint validator for links receiving data allowed by its settings.
+ */
+class LinkTypeConstraintValidator extends ConstraintValidator {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validate($value, Constraint $constraint) {
+    if (isset($value)) {
+      $uri_is_valid = TRUE;
+
+      /** @var \Drupal\link\LinkItemInterface $link_item */
+      $link_item = $value;
+      $link_type = $link_item->getFieldDefinition()->getSetting('link_type');
+
+      // Try to resolve the given URI to a URL. It may fail if it's schemeless.
+      try {
+        $url = $link_item->getUrl();
+      }
+      catch (\InvalidArgumentException $e) {
+        $uri_is_valid = FALSE;
+      }
+
+      // If the link field doesn't support both internal and external links,
+      // check whether the URL (a resolved URI) is in fact violating either
+      // restriction.
+      if ($uri_is_valid && $link_type !== LinkItemInterface::LINK_GENERIC) {
+        if (!($link_type & LinkItemInterface::LINK_EXTERNAL) && $url->isExternal()) {
+          $uri_is_valid = FALSE;
+        }
+        if (!($link_type & LinkItemInterface::LINK_INTERNAL) && !$url->isExternal()) {
+          $uri_is_valid = FALSE;
+        }
+      }
+
+      if (!$uri_is_valid) {
+        $this->context->addViolation($constraint->message, ['@uri' => $link_item->uri]);
+      }
+    }
+  }
+
+}

core/modules/link/src/Plugin/migrate/field/d6/LinkField.php

@@ -0,0 +1,49 @@
+<?php
+
+namespace Drupal\link\Plugin\migrate\field\d6;
+
+use Drupal\migrate\Plugin\MigrationInterface;
+use Drupal\migrate_drupal\Attribute\MigrateField;
+use Drupal\migrate_drupal\Plugin\migrate\field\FieldPluginBase;
+
+#[MigrateField(
+  id: 'link',
+  core: [6],
+  type_map: [
+    'link' => 'link',
+  ],
+  source_module: 'link',
+  destination_module: 'link',
+)]
+class LinkField extends FieldPluginBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFieldFormatterMap() {
+    // See d6_field_formatter_settings.yml and FieldPluginBase
+    // alterFieldFormatterMigration().
+    return [
+      'default' => 'link',
+      'plain' => 'link',
+      'absolute' => 'link',
+      'title_plain' => 'link',
+      'url' => 'link',
+      'short' => 'link',
+      'label' => 'link',
+      'separate' => 'link_separate',
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function defineValueProcessPipeline(MigrationInterface $migration, $field_name, $data) {
+    $process = [
+      'plugin' => 'field_link',
+      'source' => $field_name,
+    ];
+    $migration->mergeProcessOfProperty($field_name, $process);
+  }
+
+}

core/modules/link/src/Plugin/migrate/field/d7/LinkField.php

@@ -0,0 +1,71 @@
+<?php
+
+namespace Drupal\link\Plugin\migrate\field\d7;
+
+use Drupal\link\Plugin\migrate\field\d6\LinkField as D6LinkField;
+use Drupal\migrate\Plugin\MigrationInterface;
+use Drupal\migrate_drupal\Attribute\MigrateField;
+
+/**
+ * MigrateField Plugin for Drupal 7 link fields.
+ *
+ * This plugin provides the exact same functionality as the Drupal 6 "link"
+ * plugin with the exception that the plugin ID "link_field" is used in the
+ * field type map.
+ */
+#[MigrateField(
+  id: 'link_field',
+  core: [7],
+  type_map: [
+    'link_field' => 'link',
+  ],
+  source_module: 'link',
+  destination_module: 'link',
+)]
+class LinkField extends D6LinkField {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFieldFormatterMap() {
+    return [
+      'link_default' => 'link',
+      'link_title_plain' => 'link',
+      'link_host' => 'link',
+      'link_url' => 'link',
+      'link_plain' => 'link',
+      'link_absolute' => 'link',
+      'link_domain' => 'link',
+      'link_no_protocol' => 'link',
+      'link_short' => 'link',
+      'link_label' => 'link',
+      'link_separate' => 'link_separate',
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFieldWidgetMap() {
+    // By default, use the plugin ID for the widget types.
+    return ['link_field' => 'link_default'];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function alterFieldInstanceMigration(MigrationInterface $migration) {
+    $process = [
+      'plugin' => 'static_map',
+      'source' => 'settings/title',
+      'bypass' => TRUE,
+      'map' => [
+        'disabled' => DRUPAL_DISABLED,
+        'optional' => DRUPAL_OPTIONAL,
+        'required' => DRUPAL_REQUIRED,
+      ],
+    ];
+    $migration->mergeProcessOfProperty('settings/title', $process);
+  }
+
+}

core/modules/link/src/Plugin/migrate/process/FieldLink.php

@@ -0,0 +1,146 @@
+<?php
+
+namespace Drupal\link\Plugin\migrate\process;
+
+use Drupal\migrate\Attribute\MigrateProcess;
+use Drupal\migrate\Plugin\MigrationInterface;
+use Drupal\migrate\MigrateExecutableInterface;
+use Drupal\migrate\ProcessPluginBase;
+use Drupal\migrate\Row;
+
+/**
+ * Transform a pre-Drupal 8 formatted link for use in Drupal 8.
+ *
+ * Previous to Drupal 8, URLs didn't need to have a URI scheme assigned. The
+ * contrib link module would auto-prefix the URL with a URI scheme. A link in
+ * Drupal 8 has more validation and external links must include the URI scheme.
+ * All external URIs need to be converted to use a URI scheme.
+ *
+ * Available configuration keys
+ * - uri_scheme: (optional) The URI scheme prefix to use for URLs without a
+ *   scheme. Defaults to 'http://', which was the default in Drupal 6 and
+ *   Drupal 7.
+ *
+ * Examples:
+ *
+ * Consider a link field migration, where you want to use https:// as the
+ * prefix:
+ *
+ * @code
+ * process:
+ *   field_link:
+ *     plugin: field_link
+ *     uri_scheme: 'https://'
+ *     source: field_link
+ * @endcode
+ */
+#[MigrateProcess('field_link')]
+class FieldLink extends ProcessPluginBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function __construct(array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration) {
+    $configuration += ['uri_scheme' => 'http://'];
+    parent::__construct($configuration, $plugin_id, $plugin_definition);
+  }
+
+  /**
+   * Turn a Drupal 6/7 URI into a Drupal 8-compatible format.
+   *
+   * @param string $uri
+   *   The 'url' value from Drupal 6/7.
+   *
+   * @return string
+   *   The Drupal 8-compatible URI.
+   *
+   * @see \Drupal\link\Plugin\Field\FieldWidget\LinkWidget::getUserEnteredStringAsUri()
+   */
+  protected function canonicalizeUri($uri) {
+    // If the path starts with 2 slashes then it is always considered an
+    // external URL without an explicit protocol part.
+    // @todo Remove this when https://www.drupal.org/node/2744729 lands.
+    if (str_starts_with($uri, '//')) {
+      return $this->configuration['uri_scheme'] . ltrim($uri, '/');
+    }
+
+    // If we already have a scheme, we're fine.
+    if (parse_url($uri, PHP_URL_SCHEME)) {
+      return $uri;
+    }
+
+    // Empty URI and non-links are allowed.
+    if (empty($uri) || in_array($uri, ['<nolink>', '<none>'])) {
+      return 'route:<nolink>';
+    }
+
+    // Remove the <front> component of the URL.
+    if (str_starts_with($uri, '<front>')) {
+      $uri = substr($uri, strlen('<front>'));
+    }
+    else {
+      // List of unicode-encoded characters that were allowed in URLs,
+      // according to link module in Drupal 7. Every character between &#x00BF;
+      // and &#x00FF; (except × &#x00D7; and ÷ &#x00F7;) with the addition of
+      // &#x0152;, &#x0153; and &#x0178;.
+      // @see https://git.drupalcode.org/project/link/blob/7.x-1.5-beta2/link.module#L1382
+      // cSpell:disable-next-line
+      $link_i_chars = '¿ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõöøùúûüýþÿŒœŸ';
+
+      // Pattern specific to internal links.
+      $internal_pattern = "/^(?:[a-z0-9" . $link_i_chars . "_\-+\[\] ]+)";
+
+      $directories = "(?:\/[a-z0-9" . $link_i_chars . "_\-\.~+%=&,$'#!():;*@\[\]]*)*";
+      // Yes, four backslashes == a single backslash.
+      $query = "(?:\/?\?([?a-z0-9" . $link_i_chars . "+_|\-\.~\/\\\\%=&,$'():;*@\[\]{} ]*))";
+      $anchor = "(?:#[a-z0-9" . $link_i_chars . "_\-\.~+%=&,$'():;*@\[\]\/\?]*)";
+
+      // The rest of the path for a standard URL.
+      $end = $directories . '?' . $query . '?' . $anchor . '?$/i';
+
+      if (!preg_match($internal_pattern . $end, $uri)) {
+        $link_domains = '[a-z][a-z0-9-]{1,62}';
+
+        // Starting a parenthesis group with (?: means that it is grouped, but is not captured
+        $authentication = "(?:(?:(?:[\w\.\-\+!$&'\(\)*\+,;=" . $link_i_chars . "]|%[0-9a-f]{2})+(?::(?:[\w" . $link_i_chars . "\.\-\+%!$&'\(\)*\+,;=]|%[0-9a-f]{2})*)?)?@)";
+        $domain = '(?:(?:[a-z0-9' . $link_i_chars . ']([a-z0-9' . $link_i_chars . '\-_\[\]])*)(\.(([a-z0-9' . $link_i_chars . '\-_\[\]])+\.)*(' . $link_domains . '|[a-z]{2}))?)';
+        $ipv4 = '(?:[0-9]{1,3}(\.[0-9]{1,3}){3})';
+        $ipv6 = '(?:[0-9a-fA-F]{1,4}(\:[0-9a-fA-F]{1,4}){7})';
+        $port = '(?::([0-9]{1,5}))';
+
+        // Pattern specific to external links.
+        $external_pattern = '/^' . $authentication . '?(' . $domain . '|' . $ipv4 . '|' . $ipv6 . ' |localhost)' . $port . '?';
+        if (preg_match($external_pattern . $end, $uri)) {
+          return $this->configuration['uri_scheme'] . $uri;
+        }
+      }
+    }
+
+    // Add the internal: scheme and ensure a leading slash.
+    return 'internal:/' . ltrim($uri, '/');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function transform($value, MigrateExecutableInterface $migrate_executable, Row $row, $destination_property) {
+    $attributes = unserialize($value['attributes']);
+    // Drupal 6/7 link attributes might be double serialized.
+    if (!is_array($attributes)) {
+      $attributes = unserialize($attributes);
+    }
+
+    // In rare cases Drupal 6/7 link attributes are triple serialized. To avoid
+    // further problems with them we set them to an empty array in this case.
+    if (!is_array($attributes)) {
+      $attributes = [];
+    }
+
+    // Massage the values into the correct form for the link.
+    $route['uri'] = $this->canonicalizeUri($value['url']);
+    $route['options']['attributes'] = $attributes;
+    $route['title'] = $value['title'];
+    return $route;
+  }
+
+}

core/modules/link/templates/link-formatter-link-separate.html.twig

@@ -0,0 +1,20 @@
+{#
+/**
+ * @file
+ * Default theme implementation of a link with separate title and URL elements.
+ *
+ * Available variables:
+ * - link: The link that has already been formatted by l().
+ * - title: (optional) A descriptive or alternate title for the link, which may
+ *   be different than the actual link text.
+ *
+ * @see template_preprocess()
+ * @see template_preprocess_link_formatter_link_separate()
+ *
+ * @ingroup themeable
+ */
+#}
+{% apply spaceless %}
+  {{ title }}
+  {{ link }}
+{% endapply %}

core/modules/link/tests/modules/link_test_base_field/link_test_base_field.info.yml

@@ -0,0 +1,12 @@
+name: Link test base field
+description: Tests link field as an optional base field
+type: module
+hidden: true
+dependencies:
+  - drupal:link
+  - drupal:entity_test
+
+# Information added by Drupal.org packaging script on 2024-07-04
+version: '10.3.1'
+project: 'drupal'
+datestamp: 1720094222

core/modules/link/tests/modules/link_test_base_field/link_test_base_field.module

@@ -0,0 +1,35 @@
+<?php
+
+/**
+ * @file
+ * Contains main module functions.
+ */
+
+use Drupal\Core\Entity\EntityTypeInterface;
+use Drupal\Core\Field\BaseFieldDefinition;
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
+use Drupal\link\LinkItemInterface;
+
+/**
+ * Implements hook_entity_base_field_info().
+ */
+function link_test_base_field_entity_base_field_info(EntityTypeInterface $entity_type) {
+  $fields = [];
+  if ($entity_type->id() === 'entity_test') {
+    $fields['links'] = BaseFieldDefinition::create('link')
+      ->setLabel(t('Links'))
+      ->setRevisionable(TRUE)
+      ->setCardinality(FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED)
+      ->setDescription(t('Add links to the entity.'))
+      ->setRequired(FALSE)
+      ->setSettings([
+        'link_type' => LinkItemInterface::LINK_GENERIC,
+        'title' => DRUPAL_REQUIRED,
+      ])
+      ->setDisplayOptions('form', [
+        'type' => 'link_default',
+        'weight' => 49,
+      ]);
+  }
+  return $fields;
+}

core/modules/link/tests/modules/link_test_views/link_test_views.info.yml

@@ -0,0 +1,14 @@
+name: 'Link test views'
+type: module
+description: 'Provides default views for views link tests.'
+package: Testing
+# version: VERSION
+dependencies:
+  - drupal:node
+  - drupal:views
+  - drupal:link
+
+# Information added by Drupal.org packaging script on 2024-07-04
+version: '10.3.1'
+project: 'drupal'
+datestamp: 1720094222

core/modules/link/tests/modules/link_test_views/test_views/views.view.test_link_tokens.yml

@@ -0,0 +1,205 @@
+langcode: en
+status: true
+dependencies:
+  config:
+    - field.storage.node.field_link
+  module:
+    - link
+    - node
+    - user
+id: test_link_tokens
+label: link
+module: views
+description: ''
+tag: ''
+base_table: node_field_data
+base_field: nid
+display:
+  default:
+    display_plugin: default
+    id: default
+    display_title: Default
+    position: 0
+    display_options:
+      access:
+        type: perm
+        options:
+          perm: 'access content'
+      cache:
+        type: tag
+        options: {  }
+      query:
+        type: views_query
+        options:
+          disable_sql_rewrite: false
+          distinct: false
+          replica: false
+          query_comment: ''
+          query_tags: {  }
+      exposed_form:
+        type: basic
+        options:
+          submit_button: Apply
+          reset_button: false
+          reset_button_label: Reset
+          exposed_sorts_label: 'Sort by'
+          expose_sort_order: true
+          sort_asc_label: Asc
+          sort_desc_label: Desc
+      pager:
+        type: full
+        options:
+          items_per_page: 10
+          offset: 0
+          id: 0
+          total_pages: null
+          expose:
+            items_per_page: false
+            items_per_page_label: 'Items per page'
+            items_per_page_options: '5, 10, 25, 50'
+            items_per_page_options_all: false
+            items_per_page_options_all_label: '- All -'
+            offset: false
+            offset_label: Offset
+          tags:
+            previous: '‹ previous'
+            next: 'next ›'
+            first: '« first'
+            last: 'last »'
+          quantity: 9
+      style:
+        type: default
+      row:
+        type: fields
+        options:
+          default_field_elements: true
+          inline: {  }
+          separator: ''
+          hide_empty: false
+      fields:
+        field_link:
+          id: field_link
+          table: node__field_link
+          field: field_link
+          relationship: none
+          group_type: group
+          admin_label: ''
+          label: ''
+          exclude: false
+          alter:
+            alter_text: true
+            text: "Formatted: {{ field_link }}<br />\nRaw uri: {{ field_link__uri }}<br />\nRaw title: {{ field_link__title }}<br />\nRaw options: {{ field_link__options }}."
+            make_link: false
+            path: '{{ field_link__uri }}'
+            absolute: false
+            external: false
+            replace_spaces: false
+            path_case: none
+            trim_whitespace: false
+            alt: ''
+            rel: ''
+            link_class: ''
+            prefix: ''
+            suffix: ''
+            target: ''
+            nl2br: false
+            max_length: 0
+            word_boundary: true
+            ellipsis: true
+            more_link: false
+            more_link_text: ''
+            more_link_path: ''
+            strip_tags: false
+            trim: false
+            preserve_tags: ''
+            html: false
+          element_type: ''
+          element_class: ''
+          element_label_type: ''
+          element_label_class: ''
+          element_label_colon: false
+          element_wrapper_type: ''
+          element_wrapper_class: ''
+          element_default_classes: true
+          empty: ''
+          hide_empty: false
+          empty_zero: false
+          hide_alter_empty: true
+          click_sort_column: uri
+          type: link
+          settings:
+            trim_length: 80
+            url_only: false
+            url_plain: false
+            rel: '0'
+            target: '0'
+          group_column: ''
+          group_columns: {  }
+          group_rows: true
+          delta_limit: 0
+          delta_offset: 0
+          delta_reversed: false
+          delta_first_last: false
+          multi_type: separator
+          separator: ', '
+          field_api_classes: false
+          plugin_id: field
+      filters:
+        status:
+          value: '1'
+          table: node_field_data
+          field: status
+          plugin_id: boolean
+          entity_type: node
+          entity_field: status
+          id: status
+          expose:
+            operator: ''
+          group: 1
+      sorts:
+        created:
+          id: created
+          table: node_field_data
+          field: created
+          order: DESC
+          entity_type: node
+          entity_field: created
+          plugin_id: date
+          relationship: none
+          group_type: group
+          admin_label: ''
+          exposed: false
+          expose:
+            label: ''
+          granularity: second
+      title: link
+      header: {  }
+      footer: {  }
+      empty: {  }
+      relationships: {  }
+      arguments: {  }
+      display_extenders: {  }
+    cache_metadata:
+      contexts:
+        - 'languages:language_content'
+        - 'languages:language_interface'
+        - url.query_args
+        - 'user.node_grants:view'
+        - user.permissions
+      cacheable: false
+  page_1:
+    display_plugin: page
+    id: page_1
+    display_title: Page
+    position: 1
+    display_options:
+      display_extenders: {  }
+      path: test_link_tokens
+    cache_metadata:
+      contexts:
+        - 'languages:language_content'
+        - 'languages:language_interface'
+        - url.query_args
+        - 'user.node_grants:view'
+        - user.permissions
+      cacheable: false

core/modules/link/tests/src/Functional/GenericTest.php

@@ -0,0 +1,14 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\link\Functional;
+
+use Drupal\Tests\system\Functional\Module\GenericModuleTestBase;
+
+/**
+ * Generic module test for link.
+ *
+ * @group link
+ */
+class GenericTest extends GenericModuleTestBase {}

core/modules/link/tests/src/Functional/LinkFieldUITest.php

@@ -0,0 +1,259 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\link\Functional;
+
+use Drupal\Core\Url;
+use Drupal\Component\Utility\Html;
+use Drupal\Core\Entity\Entity\EntityFormDisplay;
+use Drupal\link\LinkItemInterface;
+use Drupal\Tests\BrowserTestBase;
+use Drupal\Tests\field_ui\Traits\FieldUiTestTrait;
+
+/**
+ * Tests link field UI functionality.
+ *
+ * @group link
+ */
+class LinkFieldUITest extends BrowserTestBase {
+
+  use FieldUiTestTrait;
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  protected static $modules = ['node', 'link', 'field_ui', 'block'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * A user that can edit content types.
+   *
+   * @var \Drupal\user\UserInterface
+   */
+  protected $adminUser;
+
+  /**
+   * A user that should see the help texts.
+   *
+   * @var \Drupal\user\Entity\User
+   */
+  protected $helpTextUser;
+
+  /**
+   * The content type to add fields to.
+   *
+   * @var \Drupal\node\Entity\NodeType
+   */
+  protected $contentType;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    $this->contentType = $this->drupalCreateContentType();
+    $this->adminUser = $this->drupalCreateUser([
+      'administer content types',
+      'administer node fields',
+      'administer node display',
+    ]);
+    $this->helpTextUser = $this->drupalCreateUser([
+      'create ' . $this->contentType->id() . ' content',
+    ]);
+    $this->drupalPlaceBlock('system_breadcrumb_block');
+  }
+
+  /**
+   * Tests the link field UI.
+   */
+  public function testFieldUI(): void {
+    foreach ($this->providerTestFieldUI() as $item) {
+      [$cardinality, $link_type, $title, $label, $field_name, $default_uri] = $item;
+      $this->runFieldUIItem($cardinality, $link_type, $title, $label, $field_name, $default_uri);
+    }
+  }
+
+  /**
+   * Provides test data for ::testFieldUI().
+   */
+  protected function providerTestFieldUI() {
+    // There are many combinations of field settings: where the description
+    // should show: variation on internal, external, both; cardinality (where
+    // the fieldset is hidden or used); and link text shown (required or
+    // optional) or disabled. There are two descriptions: field and URL help
+    // text.
+    $cardinalities = [1, 2];
+    $title_settings = [
+      DRUPAL_DISABLED,
+      DRUPAL_OPTIONAL,
+    ];
+    $link_types = [
+      LinkItemInterface::LINK_EXTERNAL => 'https://example.com',
+      LinkItemInterface::LINK_GENERIC => '',
+      LinkItemInterface::LINK_INTERNAL => '<front>',
+    ];
+
+    // Test all variations of link types on all cardinalities.
+    foreach ($cardinalities as $cardinality) {
+      foreach ($link_types as $link_type => $default_uri) {
+        // Now, test this with both the title enabled and disabled.
+        foreach ($title_settings as $title_setting) {
+          // Test both empty and non-empty labels.
+          foreach ([TRUE, FALSE] as $label_provided) {
+            // Generate a unique machine name for the field so it can be
+            // identified in the test.
+            $id = implode('_', [
+              'link',
+              $cardinality,
+              $link_type,
+              $title_setting,
+              (int) $label_provided,
+            ]);
+
+            // Use a unique label that contains some HTML.
+            $label = '<img src="https://example.com">' . $id;
+
+            yield [
+              $cardinality,
+              $link_type,
+              $title_setting,
+              $label_provided ? $label : '',
+              $id,
+              $default_uri,
+            ];
+          }
+        }
+      }
+    }
+  }
+
+  /**
+   * Tests one link field UI item.
+   *
+   * @param int $cardinality
+   *   The field cardinality.
+   * @param int $link_type
+   *   Determine if the link is external, internal or both.
+   * @param int $title
+   *   Determine if the field will display the link text field.
+   * @param string $label
+   *   The field label.
+   * @param string $field_name
+   *   The unique machine name for the field.
+   * @param string $default_uri
+   *   The default URI value.
+   */
+  public function runFieldUIItem($cardinality, $link_type, $title, $label, $field_name, $default_uri) {
+    $this->drupalLogin($this->adminUser);
+    $type_path = 'admin/structure/types/manage/' . $this->contentType->id();
+
+    // Add a link field to the newly-created type.
+    $description = 'link field description';
+    $field_edit = [
+      'description' => $description,
+      'settings[link_type]' => (int) $link_type,
+    ];
+    if (!empty($default_uri)) {
+      $field_edit['set_default_value'] = '1';
+      $field_edit['default_value_input[field_' . $field_name . '][0][uri]'] = $default_uri;
+      $field_edit['default_value_input[field_' . $field_name . '][0][title]'] = 'Default title';
+    }
+    $storage_edit = [
+      'cardinality_number' => $cardinality,
+    ];
+    $this->fieldUIAddNewField($type_path, $field_name, $label, 'link', $storage_edit, $field_edit);
+
+    // Load the formatter page to check that the settings summary does not
+    // generate warnings.
+    // @todo Mess with the formatter settings a bit here.
+    $this->drupalGet("$type_path/display");
+    $this->assertSession()->pageTextContains('Link text trimmed to 80 characters');
+
+    // Make the fields visible in the form display.
+    $form_display_id = implode('.', ['node', $this->contentType->id(), 'default']);
+    $form_display = EntityFormDisplay::load($form_display_id);
+    $form_display->setComponent($field_name, ['region' => 'content']);
+    $form_display->save();
+
+    // Log in a user that is allowed to create this content type, see if
+    // the user can see the expected help text.
+    $this->drupalLogin($this->helpTextUser);
+
+    $add_path = 'node/add/' . $this->contentType->id();
+    $this->drupalGet($add_path);
+
+    $expected_help_texts = [
+      LinkItemInterface::LINK_EXTERNAL => 'This must be an external URL such as <em class="placeholder">https://example.com</em>.',
+      LinkItemInterface::LINK_GENERIC => 'You can also enter an internal path such as <em class="placeholder">/node/add</em> or an external URL such as <em class="placeholder">https://example.com</em>. Enter <em class="placeholder">&lt;front&gt;</em> to link to the front page. Enter <em class="placeholder">&lt;nolink&gt;</em> to display link text only',
+      LinkItemInterface::LINK_INTERNAL => rtrim(Url::fromRoute('<front>', [], ['absolute' => TRUE])->toString(), '/'),
+    ];
+
+    // Check that the help texts we assume should be there, is there.
+    $this->assertFieldContainsRawText($field_name, $expected_help_texts[$link_type]);
+    if ($link_type === LinkItemInterface::LINK_INTERNAL) {
+      // Internal links have no "system" description. Test that none
+      // of the other help texts show here.
+      $this->assertNoFieldContainsRawText($field_name, $expected_help_texts[LinkItemInterface::LINK_EXTERNAL]);
+      $this->assertNoFieldContainsRawText($field_name, $expected_help_texts[LinkItemInterface::LINK_GENERIC]);
+    }
+    // Also assert that the description we made is here, no matter what the
+    // cardinality or link setting.
+    if (!empty($label)) {
+      $this->assertFieldContainsRawText($field_name, $label);
+    }
+
+    // Test the default field value is used as expected.
+    $this->assertSession()->fieldValueEquals('field_' . $field_name . '[0][uri]', $default_uri);
+  }
+
+  /**
+   * Checks that given field contains the given raw text.
+   *
+   * @param string $field_name
+   *   The name of the field to check.
+   * @param string $text
+   *   The text to check.
+   *
+   * @internal
+   */
+  protected function assertFieldContainsRawText(string $field_name, string $text): void {
+    $this->assertTrue((bool) preg_match('/' . preg_quote($text, '/') . '/ui', $this->getFieldHtml($field_name)));
+  }
+
+  /**
+   * Checks that given field does not contain the given raw text.
+   *
+   * @param string $field_name
+   *   The name of the field to check.
+   * @param string $text
+   *   The text to check.
+   *
+   * @internal
+   */
+  protected function assertNoFieldContainsRawText(string $field_name, string $text): void {
+    $this->assertFalse((bool) preg_match('/' . preg_quote($text, '/') . '/ui', $this->getFieldHtml($field_name)));
+  }
+
+  /**
+   * Returns the raw HTML for the given field.
+   *
+   * @param $field_name
+   *   The name of the field for which to return the HTML.
+   *
+   * @return string
+   *   The raw HTML.
+   */
+  protected function getFieldHtml($field_name) {
+    $css_id = Html::cleanCssIdentifier('edit-field-' . $field_name . '-wrapper');
+    return $this->xpath('//*[@id=:id]', [':id' => $css_id])[0]->getHtml();
+  }
+
+}

core/modules/link/tests/src/Functional/Views/LinkViewsTokensTest.php

@@ -0,0 +1,103 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\link\Functional\Views;
+
+use Drupal\field\Entity\FieldConfig;
+use Drupal\field\Entity\FieldStorageConfig;
+use Drupal\Tests\views\Functional\ViewTestBase;
+
+/**
+ * Tests the views integration for link tokens.
+ *
+ * @group link
+ */
+class LinkViewsTokensTest extends ViewTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  protected static $modules = ['link_test_views'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Views used by this test.
+   *
+   * @var array
+   */
+  public static $testViews = ['test_link_tokens'];
+
+  /**
+   * The field name used for the link field.
+   *
+   * @var string
+   */
+  protected $fieldName = 'field_link';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp($import_test_views = TRUE, $modules = ['link_test_views']): void {
+    parent::setUp($import_test_views, $modules);
+
+    // Create Basic page node type.
+    $this->drupalCreateContentType([
+      'type' => 'page',
+      'name' => 'Basic page',
+    ]);
+
+    // Create a field.
+    FieldStorageConfig::create([
+      'field_name' => $this->fieldName,
+      'type' => 'link',
+      'entity_type' => 'node',
+      'cardinality' => 1,
+    ])->save();
+    FieldConfig::create([
+      'field_name' => $this->fieldName,
+      'entity_type' => 'node',
+      'bundle' => 'page',
+      'label' => 'link field',
+    ])->save();
+
+  }
+
+  public function testLinkViewsTokens(): void {
+    // Array of URI's to test.
+    $uris = [
+      'http://www.example.com' => 'example.com',
+    ];
+
+    // Add nodes with the URI's and titles.
+    foreach ($uris as $uri => $title) {
+      $values = ['type' => 'page'];
+      $values[$this->fieldName][] = ['uri' => $uri, 'title' => $title, 'options' => ['attributes' => ['class' => 'test-link-class']]];
+      $this->drupalCreateNode($values);
+    }
+
+    $this->drupalGet('test_link_tokens');
+
+    foreach ($uris as $uri => $title) {
+      // Formatted link: {{ field_link }}<br />
+      $this->assertSession()->responseContains("Formatted: <a href=\"$uri\" class=\"test-link-class\">$title</a>");
+
+      // Raw uri: {{ field_link__uri }}<br />
+      $this->assertSession()->responseContains("Raw uri: $uri");
+
+      // Raw title: {{ field_link__title }}<br />
+      $this->assertSession()->responseContains("Raw title: $title");
+
+      // Raw options: {{ field_link__options }}<br />
+      // Options is an array and should return empty after token replace.
+      $this->assertSession()->responseContains("Raw options: .");
+    }
+  }
+
+}

core/modules/link/tests/src/FunctionalJavascript/LinkFieldFormStatesTest.php

@@ -0,0 +1,80 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\link\FunctionalJavascript;
+
+use Drupal\FunctionalJavascriptTests\WebDriverTestBase;
+
+/**
+ * Tests link field form states functionality.
+ *
+ * @group link
+ */
+class LinkFieldFormStatesTest extends WebDriverTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'entity_test',
+    'link',
+    'node',
+    'link_test_base_field',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->drupalLogin($this->drupalCreateUser([
+      'administer entity_test content',
+    ]));
+  }
+
+  /**
+   * @dataProvider linkFieldFormStatesData
+   */
+  public function testLinkFieldFormStates(string $uri, string $title): void {
+    $this->drupalGet('entity_test/add');
+    $session = $this->assertSession();
+    $session->elementNotExists('css', '#edit-links-0-uri[required]');
+    $session->elementNotExists('css', '#edit-links-0-title[required]');
+
+    $page = $this->getSession()->getPage();
+
+    if ($uri !== '') {
+      $page->fillField('links[0][uri]', $uri);
+      $session->elementNotExists('css', '#edit-links-0-uri[required]');
+      $session->elementExists('css', '#edit-links-0-title[required]');
+    }
+    else {
+      $page->fillField('links[0][title]', $title);
+      $session->elementExists('css', '#edit-links-0-uri[required]');
+      $session->elementNotExists('css', '#edit-links-0-title[required]');
+    }
+  }
+
+  /**
+   * Provides data for ::testLinkFieldJSFormStates.
+   */
+  public static function linkFieldFormStatesData() {
+    return [
+      'Fill uri, keep title empty' => [
+        'https://example.com',
+        '',
+      ],
+      'Fill title, keep uri empty' => [
+        '',
+        'https://example.com',
+      ],
+    ];
+  }
+
+}

core/modules/link/tests/src/Kernel/LinkItemSerializationTest.php

@@ -0,0 +1,107 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\link\Kernel;
+
+use Drupal\field\Entity\FieldStorageConfig;
+use Drupal\field\Entity\FieldConfig;
+use Drupal\link\LinkItemInterface;
+use Drupal\entity_test\Entity\EntityTest;
+use Drupal\Component\Utility\UrlHelper;
+use Drupal\Tests\field\Kernel\FieldKernelTestBase;
+
+/**
+ * Tests link field serialization.
+ *
+ * @group link
+ */
+class LinkItemSerializationTest extends FieldKernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['link', 'serialization'];
+
+  /**
+   * The serializer service.
+   *
+   * @var \Symfony\Component\Serializer\SerializerInterface
+   */
+  protected $serializer;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    $this->installEntitySchema('user');
+    $this->serializer = \Drupal::service('serializer');
+
+    // Create a generic, external, and internal link fields for validation.
+    FieldStorageConfig::create([
+      'entity_type' => 'entity_test',
+      'field_name' => 'field_test',
+      'type' => 'link',
+    ])->save();
+
+    FieldConfig::create([
+      'entity_type' => 'entity_test',
+      'field_name' => 'field_test',
+      'bundle' => 'entity_test',
+      'settings' => ['link_type' => LinkItemInterface::LINK_GENERIC],
+    ])->save();
+  }
+
+  /**
+   * Tests the serialization.
+   */
+  public function testLinkSerialization(): void {
+    // Create entity.
+    $entity = EntityTest::create();
+    $url = 'https://www.drupal.org?test_param=test_value';
+    $parsed_url = UrlHelper::parse($url);
+    $title = $this->randomMachineName();
+    $class = $this->randomMachineName();
+    $entity->field_test->uri = $parsed_url['path'];
+    $entity->field_test->title = $title;
+    $entity->field_test->first()
+      ->get('options')
+      ->set('query', $parsed_url['query']);
+    $entity->field_test->first()
+      ->get('options')
+      ->set('attributes', ['class' => $class]);
+    $entity->save();
+    $serialized = $this->serializer->serialize($entity, 'json');
+    $deserialized = $this->serializer->deserialize($serialized, EntityTest::class, 'json');
+    $options_expected = [
+      'query' => $parsed_url['query'],
+      'attributes' => ['class' => $class],
+    ];
+    $this->assertSame($options_expected, $deserialized->field_test->options);
+  }
+
+  /**
+   * Tests the deserialization.
+   */
+  public function testLinkDeserialization(): void {
+    // Create entity.
+    $entity = EntityTest::create();
+    $url = 'https://www.drupal.org?test_param=test_value';
+    $parsed_url = UrlHelper::parse($url);
+    $title = $this->randomMachineName();
+    $entity->field_test->uri = $parsed_url['path'];
+    $entity->field_test->title = $title;
+    $entity->field_test->first()
+      ->get('options')
+      ->set('query', $parsed_url['query']);
+    $json = json_decode($this->serializer->serialize($entity, 'json'), TRUE);
+    $json['field_test'][0]['options'] = 'string data';
+    $serialized = json_encode($json);
+    $this->expectException(\LogicException::class);
+    $this->expectExceptionMessage('The generic FieldItemNormalizer cannot denormalize string values for "options" properties of the "field_test" field (field item class: Drupal\link\Plugin\Field\FieldType\LinkItem).');
+    $this->serializer->deserialize($serialized, EntityTest::class, 'json');
+  }
+
+}

core/modules/link/tests/src/Kernel/LinkItemTest.php

@@ -0,0 +1,183 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\link\Kernel;
+
+use Drupal\Component\Utility\UrlHelper;
+use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Field\FieldItemInterface;
+use Drupal\Core\Url;
+use Drupal\entity_test\Entity\EntityTest;
+use Drupal\field\Entity\FieldConfig;
+use Drupal\field\Entity\FieldStorageConfig;
+use Drupal\Tests\field\Kernel\FieldKernelTestBase;
+use Drupal\link\LinkItemInterface;
+
+/**
+ * Tests the new entity API for the link field type.
+ *
+ * @group link
+ */
+class LinkItemTest extends FieldKernelTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  protected static $modules = ['link'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    // Create a generic, external, and internal link fields for validation.
+    FieldStorageConfig::create([
+      'field_name' => 'field_test',
+      'entity_type' => 'entity_test',
+      'type' => 'link',
+    ])->save();
+    FieldConfig::create([
+      'entity_type' => 'entity_test',
+      'field_name' => 'field_test',
+      'bundle' => 'entity_test',
+      'settings' => ['link_type' => LinkItemInterface::LINK_GENERIC],
+    ])->save();
+    FieldStorageConfig::create([
+      'field_name' => 'field_test_external',
+      'entity_type' => 'entity_test',
+      'type' => 'link',
+    ])->save();
+    FieldConfig::create([
+      'entity_type' => 'entity_test',
+      'field_name' => 'field_test_external',
+      'bundle' => 'entity_test',
+      'settings' => ['link_type' => LinkItemInterface::LINK_EXTERNAL],
+    ])->save();
+    FieldStorageConfig::create([
+      'field_name' => 'field_test_internal',
+      'entity_type' => 'entity_test',
+      'type' => 'link',
+    ])->save();
+    FieldConfig::create([
+      'entity_type' => 'entity_test',
+      'field_name' => 'field_test_internal',
+      'bundle' => 'entity_test',
+      'settings' => ['link_type' => LinkItemInterface::LINK_INTERNAL],
+    ])->save();
+  }
+
+  /**
+   * Tests using entity fields of the link field type.
+   */
+  public function testLinkItem(): void {
+    // Create entity.
+    $entity = EntityTest::create();
+    $url = 'https://www.drupal.org?test_param=test_value';
+    $parsed_url = UrlHelper::parse($url);
+    $title = $this->randomMachineName();
+    $class = $this->randomMachineName();
+    $entity->field_test->uri = $parsed_url['path'];
+    $entity->field_test->title = $title;
+    $entity->field_test->first()->get('options')->set('query', $parsed_url['query']);
+    $entity->field_test->first()->get('options')->set('attributes', ['class' => $class]);
+    $this->assertEquals([
+      'query' => $parsed_url['query'],
+      'attributes' => [
+        'class' => $class,
+      ],
+      'external' => TRUE,
+    ], $entity->field_test->first()->getUrl()->getOptions());
+    $entity->name->value = $this->randomMachineName();
+    $entity->save();
+
+    // Verify that the field value is changed.
+    $id = $entity->id();
+    $entity = EntityTest::load($id);
+    $this->assertInstanceOf(FieldItemListInterface::class, $entity->field_test);
+    $this->assertInstanceOf(FieldItemInterface::class, $entity->field_test[0]);
+    $this->assertEquals($parsed_url['path'], $entity->field_test->uri);
+    $this->assertEquals($parsed_url['path'], $entity->field_test[0]->uri);
+    $this->assertEquals($title, $entity->field_test->title);
+    $this->assertEquals($title, $entity->field_test[0]->title);
+    $this->assertEquals($title, $entity->field_test[0]->getTitle());
+    $this->assertEquals($class, $entity->field_test->options['attributes']['class']);
+    $this->assertEquals($parsed_url['query'], $entity->field_test->options['query']);
+
+    // Update only the entity name property to check if the link field data will
+    // remain intact.
+    $entity->name->value = $this->randomMachineName();
+    $entity->save();
+    $id = $entity->id();
+    $entity = EntityTest::load($id);
+    $this->assertEquals($parsed_url['path'], $entity->field_test->uri);
+    $this->assertEquals($class, $entity->field_test->options['attributes']['class']);
+    $this->assertEquals($parsed_url['query'], $entity->field_test->options['query']);
+
+    // Verify changing the field value.
+    $new_url = 'https://www.drupal.org';
+    $new_title = $this->randomMachineName();
+    $new_class = $this->randomMachineName();
+    $entity->field_test->uri = $new_url;
+    $entity->field_test->title = $new_title;
+    $entity->field_test->first()->get('options')->set('query', NULL);
+    $entity->field_test->first()->get('options')->set('attributes', ['class' => $new_class]);
+    $this->assertEquals($new_url, $entity->field_test->uri);
+    $this->assertEquals($new_title, $entity->field_test->title);
+    $this->assertEquals($new_class, $entity->field_test->options['attributes']['class']);
+    $this->assertNull($entity->field_test->options['query']);
+
+    // Read changed entity and assert changed values.
+    $entity->save();
+    $entity = EntityTest::load($id);
+    $this->assertEquals($new_url, $entity->field_test->uri);
+    $this->assertEquals($new_title, $entity->field_test->title);
+    $this->assertEquals($new_class, $entity->field_test->options['attributes']['class']);
+
+    // Check that if we only set uri the default values for title and options
+    // are also initialized.
+    $entity->field_test = ['uri' => 'internal:/node/add'];
+    $this->assertEquals('internal:/node/add', $entity->field_test->uri);
+    $this->assertNull($entity->field_test->title);
+    $this->assertSame([], $entity->field_test->options);
+
+    // Check that if we set uri and options then the default values are properly
+    // initialized.
+    $entity->field_test = [
+      'uri' => 'internal:/node/add',
+      'options' => ['query' => NULL],
+    ];
+    $this->assertEquals('internal:/node/add', $entity->field_test->uri);
+    $this->assertNull($entity->field_test->title);
+    $this->assertNull($entity->field_test->options['query']);
+
+    // Check that if we set the direct value of link field it correctly set the
+    // uri and the default values of the field.
+    $entity->field_test = 'internal:/node/add';
+    $this->assertEquals('internal:/node/add', $entity->field_test->uri);
+    $this->assertNull($entity->field_test->title);
+    $this->assertSame([], $entity->field_test->options);
+
+    // Check that setting options to NULL does not trigger an error when
+    // calling getUrl();
+    $entity->field_test->options = NULL;
+    $this->assertInstanceOf(Url::class, $entity->field_test[0]->getUrl());
+
+    // Check that setting LinkItem value NULL doesn't generate any error or
+    // warning.
+    $entity->field_test[0] = NULL;
+    $this->assertNull($entity->field_test[0]->getValue());
+
+    // Test the generateSampleValue() method for generic, external, and internal
+    // link types.
+    $entity = EntityTest::create();
+    $entity->field_test->generateSampleItems();
+    $entity->field_test_external->generateSampleItems();
+    $entity->field_test_internal->generateSampleItems();
+    $this->entityValidateAndSave($entity);
+  }
+
+}

core/modules/link/tests/src/Kernel/LinkItemUrlValidationTest.php

@@ -0,0 +1,124 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\link\Kernel;
+
+use Drupal\Tests\field\Kernel\FieldKernelTestBase;
+
+/**
+ * Tests link field validation.
+ *
+ * @group link
+ */
+class LinkItemUrlValidationTest extends FieldKernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['link'];
+
+  /**
+   * Tests link validation.
+   */
+  public function testExternalLinkValidation(): void {
+    $definition = \Drupal::typedDataManager()
+      ->createDataDefinition('field_item:link');
+    $link_item = \Drupal::typedDataManager()->create($definition);
+    $test_links = $this->getTestLinks();
+
+    foreach ($test_links as $data) {
+      [$value, $expected_violations] = $data;
+      $link_item->setValue($value);
+      $violations = $link_item->validate();
+      $expected_count = count($expected_violations);
+      $this->assertCount($expected_count, $violations, sprintf('Violation message count error for %s', $value));
+      if ($expected_count) {
+        $i = 0;
+        foreach ($expected_violations as $error_msg) {
+          // If the expected message contains a '%' add the current link value.
+          if (strpos($error_msg, '%')) {
+            $error_msg = sprintf($error_msg, $value);
+          }
+          $this->assertEquals($error_msg, $violations[$i++]->getMessage());
+        }
+      }
+    }
+  }
+
+  /**
+   * Builds an array of links to test.
+   *
+   * @return array
+   *   The first element of the array is the link value to test. The second
+   *   value is an array of expected violation messages.
+   */
+  protected function getTestLinks() {
+    $violation_0 = "The path '%s' is invalid.";
+    $violation_1 = 'This value should be of the correct primitive type.';
+    return [
+      ['invalid://not-a-valid-protocol', [$violation_0]],
+      ['http://www.example.com/', []],
+      // Strings within parenthesis without leading space char.
+      ['http://www.example.com/strings_(string_within_parenthesis)', []],
+      // Numbers within parenthesis without leading space char.
+      ['http://www.example.com/numbers_(9999)', []],
+      ['http://www.example.com/?name=ferret&color=purple', []],
+      ['http://www.example.com/page?name=ferret&color=purple', []],
+      ['http://www.example.com?a=&b[]=c&d[]=e&d[]=f&h==', []],
+      ['http://www.example.com#colors', []],
+      // Use list of valid URLS from],
+      // https://cran.r-project.org/web/packages/rex/vignettes/url_parsing.html.
+      ["http://foo.com/blah_blah", []],
+      ["http://foo.com/blah_blah/", []],
+      ["http://foo.com/blah_blah_(wikipedia)", []],
+      ["http://foo.com/blah_blah_(wikipedia)_(again)", []],
+      ["http://www.example.com/wpstyle/?p=364", []],
+      ["https://www.example.com/foo/?bar=baz&inga=42&quux", []],
+      ["http://✪df.ws/123", []],
+      ["http://userid:password@example.com:8080", []],
+      ["http://userid:password@example.com:8080/", []],
+      ["http://userid@example.com", []],
+      ["http://userid@example.com/", []],
+      ["http://userid@example.com:8080", []],
+      ["http://userid@example.com:8080/", []],
+      ["http://userid:password@example.com", []],
+      ["http://userid:password@example.com/", []],
+      ["http://➡.ws/䨹", []],
+      ["http://⌘.ws", []],
+      ["http://⌘.ws/", []],
+      ["http://foo.com/blah_(wikipedia)#cite-1", []],
+      ["http://foo.com/blah_(wikipedia)_blah#cite-1", []],
+      // The following invalid URLs produce false positives.
+      ["http://foo.com/unicode_(✪)_in_parens", []],
+      ["http://foo.com/(something)?after=parens", []],
+      ["http://☺.damowmow.com/", []],
+      ["http://code.google.com/events/#&product=browser", []],
+      ["http://j.mp", []],
+      ["ftp://foo.bar/baz", []],
+      ["http://foo.bar/?q=Test%20URL-encoded%20stuff", []],
+      ["http://مثال.إختبار", []],
+      ["http://例子.测试", []],
+      ["http://-.~_!$&'()*+,;=:%40:80%2f::::::@example.com", []],
+      ["http://1337.net", []],
+      ["http://a.b-c.de", []],
+      ["radar://1234", [$violation_0]],
+      ["h://test", [$violation_0]],
+      ["ftps://foo.bar/", [$violation_0]],
+      // Use invalid URLS from
+      // https://cran.r-project.org/web/packages/rex/vignettes/url_parsing.html.
+      ['http://', [$violation_0, $violation_1]],
+      ["http://?", [$violation_0, $violation_1]],
+      ["http://??", [$violation_0, $violation_1]],
+      ["http://??/", [$violation_0, $violation_1]],
+      ["http://#", [$violation_0, $violation_1]],
+      ["http://##", [$violation_0, $violation_1]],
+      ["http://##/", [$violation_0, $violation_1]],
+      ["//", [$violation_0, $violation_1]],
+      ["///a", [$violation_0, $violation_1]],
+      ["///", [$violation_0, $violation_1]],
+      ["http:///a", [$violation_0, $violation_1]],
+    ];
+  }
+
+}

core/modules/link/tests/src/Kernel/Plugin/migrate/field/d7/LinkFieldTest.php

@@ -0,0 +1,74 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\link\Kernel\Plugin\migrate\field\d7;
+
+use Drupal\KernelTests\KernelTestBase;
+use Drupal\migrate\Plugin\MigrationInterface;
+use Drupal\link\Plugin\migrate\field\d7\LinkField;
+use Prophecy\Argument;
+
+/**
+ * @coversDefaultClass \Drupal\link\Plugin\migrate\field\d7\LinkField
+ * @group link
+ */
+class LinkFieldTest extends KernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['system'];
+
+  /**
+   * @var \Drupal\migrate_drupal\Plugin\MigrateFieldInterface
+   */
+  protected $plugin;
+
+  /**
+   * @var \Drupal\migrate\Plugin\MigrationInterface
+   */
+  protected $migration;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    $this->plugin = new LinkField([], 'link', []);
+
+    $migration = $this->prophesize(MigrationInterface::class);
+
+    // The plugin's alterFieldInstanceMigration() method will call
+    // mergeProcessOfProperty() and return nothing. So, in order to examine the
+    // process pipeline created by the plugin, we need to ensure that
+    // getProcess() always returns the last input to mergeProcessOfProperty().
+    $migration->mergeProcessOfProperty(Argument::type('string'), Argument::type('array'))
+      ->will(function ($arguments) use ($migration) {
+        $migration->getProcess()->willReturn($arguments[1]);
+      });
+
+    $this->migration = $migration->reveal();
+  }
+
+  /**
+   * @covers ::alterFieldInstanceMigration
+   */
+  public function testAlterFieldInstanceMigration($method = 'alterFieldInstanceMigration'): void {
+    $this->plugin->$method($this->migration);
+
+    $expected = [
+      'plugin' => 'static_map',
+      'source' => 'settings/title',
+      'bypass' => TRUE,
+      'map' => [
+        'disabled' => DRUPAL_DISABLED,
+        'optional' => DRUPAL_OPTIONAL,
+        'required' => DRUPAL_REQUIRED,
+      ],
+    ];
+    $this->assertSame($expected, $this->migration->getProcess());
+  }
+
+}

core/modules/link/tests/src/Unit/LinkFormatterTest.php

@@ -0,0 +1,155 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\link\Unit;
+
+use Drupal\Core\DependencyInjection\ContainerBuilder;
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Field\FieldDefinitionInterface;
+use Drupal\Core\Field\FieldItemList;
+use Drupal\Core\Field\FieldTypePluginManagerInterface;
+use Drupal\Core\Path\PathValidatorInterface;
+use Drupal\Core\Routing\UrlGenerator;
+use Drupal\Core\Url;
+use Drupal\link\LinkItemInterface;
+use Drupal\link\Plugin\Field\FieldFormatter\LinkFormatter;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * Tests the Field Formatter for the link field type.
+ *
+ * @group link
+ */
+class LinkFormatterTest extends UnitTestCase {
+
+  /**
+   * Tests when LinkItem::getUrl with malformed URL renders empty link.
+   *
+   * LinkItem::getUrl will throw \InvalidArgumentException.
+   */
+  public function testFormatterLinkItemUrlMalformed(): void {
+    $entity = $this->createMock(EntityInterface::class);
+
+    $linkItem = $this->createMock(LinkItemInterface::class);
+    $exception = new \InvalidArgumentException();
+    $linkItem->expects($this->any())
+      ->method('getParent')
+      ->willReturn($entity);
+    $linkItem->expects($this->once())
+      ->method('getUrl')
+      ->willThrowException($exception);
+    $linkItem->expects($this->any())
+      ->method('__get')
+      ->with('options')
+      ->willReturn([]);
+    $fieldDefinition = $this->createMock(FieldDefinitionInterface::class);
+    $fieldList = new FieldItemList($fieldDefinition, '', $linkItem);
+
+    $fieldTypePluginManager = $this->createMock(FieldTypePluginManagerInterface::class);
+    $fieldTypePluginManager->expects($this->once())
+      ->method('createFieldItem')
+      ->willReturn($linkItem);
+    $urlGenerator = $this->createMock(UrlGenerator::class);
+    $urlGenerator->expects($this->once())
+      ->method('generateFromRoute')
+      ->with('<none>', [], [], FALSE)
+      ->willReturn('http://example.com');
+    $container = new ContainerBuilder();
+    $container->set('plugin.manager.field.field_type', $fieldTypePluginManager);
+    $container->set('url_generator', $urlGenerator);
+    \Drupal::setContainer($container);
+    $fieldList->setValue([$linkItem]);
+
+    $pathValidator = $this->createMock(PathValidatorInterface::class);
+    $linkFormatter = new LinkFormatter('', [], $fieldDefinition, [], '', '', [], $pathValidator);
+    $elements = $linkFormatter->viewElements($fieldList, 'es');
+    $this->assertEquals('link', $elements[0]['#type']);
+  }
+
+  /**
+   * Tests when LinkItem::getUrl throws an unexpected exception.
+   */
+  public function testFormatterLinkItemUrlUnexpectedException(): void {
+    $exception = new \Exception('Unexpected!!!');
+
+    $linkItem = $this->createMock(LinkItemInterface::class);
+    $entity = $this->createMock(EntityInterface::class);
+    $linkItem->expects($this->any())
+      ->method('getParent')
+      ->willReturn($entity);
+    $linkItem->expects($this->once())
+      ->method('getUrl')
+      ->willThrowException($exception);
+    $linkItem->expects($this->any())
+      ->method('__get')
+      ->with('options')
+      ->willReturn([]);
+    $fieldDefinition = $this->createMock(FieldDefinitionInterface::class);
+    $fieldList = new FieldItemList($fieldDefinition, '', $linkItem);
+
+    $fieldTypePluginManager = $this->createMock(FieldTypePluginManagerInterface::class);
+    $fieldTypePluginManager->expects($this->once())
+      ->method('createFieldItem')
+      ->willReturn($linkItem);
+    $container = new ContainerBuilder();
+    $container->set('plugin.manager.field.field_type', $fieldTypePluginManager);
+    \Drupal::setContainer($container);
+    $fieldList->setValue([$linkItem]);
+
+    $pathValidator = $this->createMock(PathValidatorInterface::class);
+    $linkFormatter = new LinkFormatter('', [], $fieldDefinition, [], '', '', [], $pathValidator);
+    $this->expectException(\Exception::class);
+    $this->expectExceptionMessage('Unexpected!!!');
+    $linkFormatter->viewElements($fieldList, 'fr');
+  }
+
+  /**
+   * Tests when LinkItem::getUrl returns a functional URL.
+   */
+  public function testFormatterLinkItem(): void {
+    $expectedUrl = Url::fromUri('route:<front>');
+
+    $linkItem = $this->createMock(LinkItemInterface::class);
+    $entity = $this->createMock(EntityInterface::class);
+    $linkItem->expects($this->any())
+      ->method('getParent')
+      ->willReturn($entity);
+    $linkItem->expects($this->once())
+      ->method('getUrl')
+      ->willReturn($expectedUrl);
+    $linkItem->expects($this->any())
+      ->method('__get')
+      ->with('options')
+      ->willReturn([]);
+    $fieldDefinition = $this->createMock(FieldDefinitionInterface::class);
+    $fieldList = new FieldItemList($fieldDefinition, '', $linkItem);
+
+    $fieldTypePluginManager = $this->createMock(FieldTypePluginManagerInterface::class);
+    $fieldTypePluginManager->expects($this->once())
+      ->method('createFieldItem')
+      ->willReturn($linkItem);
+    $urlGenerator = $this->createMock(UrlGenerator::class);
+    $urlGenerator->expects($this->once())
+      ->method('generateFromRoute')
+      ->with('<front>', [], [], FALSE)
+      ->willReturn('http://example.com');
+    $container = new ContainerBuilder();
+    $container->set('plugin.manager.field.field_type', $fieldTypePluginManager);
+    $container->set('url_generator', $urlGenerator);
+    \Drupal::setContainer($container);
+    $fieldList->setValue([$linkItem]);
+
+    $pathValidator = $this->createMock(PathValidatorInterface::class);
+    $linkFormatter = new LinkFormatter('', [], $fieldDefinition, [], '', '', [], $pathValidator);
+    $elements = $linkFormatter->viewElements($fieldList, 'zh');
+    $this->assertEquals([
+      [
+        '#type' => 'link',
+        '#title' => 'http://example.com',
+        '#url' => $expectedUrl,
+      ],
+    ], $elements);
+  }
+
+}

core/modules/link/tests/src/Unit/Plugin/Validation/Constraint/LinkAccessConstraintValidatorTest.php

@@ -0,0 +1,86 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\link\Unit\Plugin\Validation\Constraint;
+
+use Drupal\link\Plugin\Validation\Constraint\LinkAccessConstraint;
+use Drupal\link\Plugin\Validation\Constraint\LinkAccessConstraintValidator;
+use Drupal\Tests\UnitTestCase;
+use Symfony\Component\Validator\Context\ExecutionContextInterface;
+
+/**
+ * Tests the LinkAccessConstraintValidator validator.
+ *
+ * @coversDefaultClass \Drupal\link\Plugin\Validation\Constraint\LinkAccessConstraintValidator
+ * @group validation
+ */
+class LinkAccessConstraintValidatorTest extends UnitTestCase {
+
+  /**
+   * Tests the access validation constraint for links.
+   *
+   * @covers ::validate
+   * @dataProvider providerValidate
+   */
+  public function testValidate(bool $mayLinkAnyPage, bool $urlAccess, bool $valid): void {
+    // Mock a Url object that returns a boolean indicating user access.
+    $url = $this->getMockBuilder('Drupal\Core\Url')
+      ->disableOriginalConstructor()
+      ->getMock();
+    if ($mayLinkAnyPage) {
+      $url->expects($this->never())
+        ->method('access');
+    }
+    else {
+      $url->expects($this->once())
+        ->method('access')
+        ->willReturn($urlAccess);
+    }
+
+    // Mock a link object that returns the URL object.
+    $link = $this->createMock('Drupal\link\LinkItemInterface');
+    $link->expects($this->any())
+      ->method('getUrl')
+      ->willReturn($url);
+
+    // Mock a user object that returns a boolean indicating user access to all
+    // links.
+    $user = $this->createMock('Drupal\Core\Session\AccountProxyInterface');
+    $user->expects($this->any())
+      ->method('hasPermission')
+      ->with($this->equalTo('link to any page'))
+      ->willReturn($mayLinkAnyPage);
+
+    $context = $this->createMock(ExecutionContextInterface::class);
+    if ($valid) {
+      $context->expects($this->never())
+        ->method('addViolation');
+    }
+    else {
+      $context->expects($this->once())
+        ->method('addViolation');
+    }
+
+    $constraint = new LinkAccessConstraint();
+    $validate = new LinkAccessConstraintValidator($user);
+    $validate->initialize($context);
+    $validate->validate($link, $constraint);
+  }
+
+  /**
+   * Data provider for LinkAccessConstraintValidator::validate().
+   *
+   * @return array
+   *   An array of tests, matching the parameter inputs for testValidate.
+   *
+   * @see \Drupal\Tests\link\LinkAccessConstraintValidatorTest::validate()
+   */
+  public static function providerValidate(): \Generator {
+    yield [TRUE, TRUE, TRUE];
+    yield [TRUE, FALSE, TRUE];
+    yield [FALSE, TRUE, TRUE];
+    yield [FALSE, FALSE, FALSE];
+  }
+
+}

core/modules/link/tests/src/Unit/Plugin/Validation/Constraint/LinkExternalProtocolsConstraintValidatorTest.php

@@ -0,0 +1,111 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\link\Unit\Plugin\Validation\Constraint;
+
+use Drupal\Component\Utility\UrlHelper;
+use Drupal\Core\Url;
+use Drupal\link\Plugin\Validation\Constraint\LinkExternalProtocolsConstraint;
+use Drupal\link\Plugin\Validation\Constraint\LinkExternalProtocolsConstraintValidator;
+use Drupal\Tests\UnitTestCase;
+use Symfony\Component\Validator\Context\ExecutionContextInterface;
+
+/**
+ * @coversDefaultClass \Drupal\link\Plugin\Validation\Constraint\LinkExternalProtocolsConstraintValidator
+ * @group Link
+ */
+class LinkExternalProtocolsConstraintValidatorTest extends UnitTestCase {
+
+  /**
+   * @covers ::validate
+   * @dataProvider providerValidate
+   * @runInSeparateProcess
+   */
+  public function testValidate($url, $valid): void {
+    $link = $this->createMock('Drupal\link\LinkItemInterface');
+    $link->expects($this->any())
+      ->method('getUrl')
+      ->willReturn(Url::fromUri($url));
+    $context = $this->createMock(ExecutionContextInterface::class);
+
+    if ($valid) {
+      $context->expects($this->never())
+        ->method('addViolation');
+    }
+    else {
+      $context->expects($this->once())
+        ->method('addViolation');
+    }
+
+    // Setup some more allowed protocols.
+    UrlHelper::setAllowedProtocols(['http', 'https', 'magnet']);
+
+    $constraint = new LinkExternalProtocolsConstraint();
+
+    $validator = new LinkExternalProtocolsConstraintValidator();
+    $validator->initialize($context);
+    $validator->validate($link, $constraint);
+  }
+
+  /**
+   * Data provider for ::testValidate.
+   */
+  public static function providerValidate() {
+    $data = [];
+
+    // Test allowed protocols.
+    $data[] = ['http://www.example.com', TRUE];
+    $data[] = ['https://www.example.com', TRUE];
+    // cSpell:disable-next-line
+    $data[] = ['magnet:?xt=urn:sha1:YNCKHTQCWBTRNJIV4WNAE52SJUQCZO5C', TRUE];
+
+    // Invalid protocols.
+    $data[] = ['ftp://ftp.funet.fi/pub/standards/RFC/rfc959.txt', FALSE];
+
+    return $data;
+  }
+
+  /**
+   * @covers ::validate
+   *
+   * @see \Drupal\Core\Url::fromUri
+   */
+  public function testValidateWithMalformedUri(): void {
+    $link = $this->createMock('Drupal\link\LinkItemInterface');
+    $link->expects($this->any())
+      ->method('getUrl')
+      ->willThrowException(new \InvalidArgumentException());
+
+    $context = $this->createMock(ExecutionContextInterface::class);
+    $context->expects($this->never())
+      ->method('addViolation');
+
+    $constraint = new LinkExternalProtocolsConstraint();
+
+    $validator = new LinkExternalProtocolsConstraintValidator();
+    $validator->initialize($context);
+    $validator->validate($link, $constraint);
+  }
+
+  /**
+   * @covers ::validate
+   */
+  public function testValidateIgnoresInternalUrls(): void {
+    $link = $this->createMock('Drupal\link\LinkItemInterface');
+    $link->expects($this->any())
+      ->method('getUrl')
+      ->willReturn(Url::fromRoute('example.test'));
+
+    $context = $this->createMock(ExecutionContextInterface::class);
+    $context->expects($this->never())
+      ->method('addViolation');
+
+    $constraint = new LinkExternalProtocolsConstraint();
+
+    $validator = new LinkExternalProtocolsConstraintValidator();
+    $validator->initialize($context);
+    $validator->validate($link, $constraint);
+  }
+
+}

core/modules/link/tests/src/Unit/Plugin/Validation/Constraint/LinkNotExistingInternalConstraintValidatorTest.php

@@ -0,0 +1,118 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\link\Unit\Plugin\Validation\Constraint;
+
+use Drupal\Core\Routing\UrlGeneratorInterface;
+use Drupal\Core\Url;
+use Drupal\link\LinkItemInterface;
+use Drupal\link\Plugin\Validation\Constraint\LinkNotExistingInternalConstraint;
+use Drupal\link\Plugin\Validation\Constraint\LinkNotExistingInternalConstraintValidator;
+use Drupal\Tests\UnitTestCase;
+use PHPUnit\Framework\MockObject\MockObject;
+use Symfony\Component\Routing\Exception\RouteNotFoundException;
+use Symfony\Component\Validator\Context\ExecutionContextInterface;
+
+/**
+ * @coversDefaultClass \Drupal\link\Plugin\Validation\Constraint\LinkNotExistingInternalConstraintValidator
+ * @group Link
+ */
+class LinkNotExistingInternalConstraintValidatorTest extends UnitTestCase {
+
+  /**
+   * @covers ::validate
+   */
+  public function testValidateFromUri(): void {
+    $url = Url::fromUri('https://www.drupal.org');
+
+    $link = $this->createMock(LinkItemInterface::class);
+    $link->expects($this->any())
+      ->method('getUrl')
+      ->willReturn($url);
+
+    $context = $this->createMock(ExecutionContextInterface::class);
+    $context->expects($this->never())
+      ->method('addViolation');
+
+    $this->validate($link, $context);
+  }
+
+  /**
+   * @covers ::validate
+   */
+  public function testValidateFromRoute(): void {
+    $url = Url::fromRoute('example.existing_route');
+
+    $urlGenerator = $this->createMock(UrlGeneratorInterface::class);
+    $urlGenerator->expects($this->any())
+      ->method('generateFromRoute')
+      ->with('example.existing_route', [], [])
+      ->willReturn('/example/existing');
+    $url->setUrlGenerator($urlGenerator);
+
+    $link = $this->createMock(LinkItemInterface::class);
+    $link->expects($this->any())
+      ->method('getUrl')
+      ->willReturn($url);
+
+    $context = $this->createMock(ExecutionContextInterface::class);
+    $context->expects($this->never())
+      ->method('addViolation');
+
+    $this->validate($link, $context);
+  }
+
+  /**
+   * @covers ::validate
+   */
+  public function testValidateFromNonExistingRoute(): void {
+    $url = Url::fromRoute('example.not_existing_route');
+
+    $urlGenerator = $this->createMock(UrlGeneratorInterface::class);
+    $urlGenerator->expects($this->any())
+      ->method('generateFromRoute')
+      ->with('example.not_existing_route', [], [])
+      ->willReturn(new RouteNotFoundException());
+    $url->setUrlGenerator($urlGenerator);
+
+    $link = $this->createMock(LinkItemInterface::class);
+    $link->expects($this->any())
+      ->method('getUrl')
+      ->willReturn($url);
+
+    $context = $this->createMock(ExecutionContextInterface::class);
+    $context->expects($this->never())
+      ->method('addViolation');
+
+    $this->validate($link, $context);
+  }
+
+  /**
+   * @covers ::validate
+   *
+   * @see \Drupal\Core\Url::fromUri
+   */
+  public function testValidateWithMalformedUri(): void {
+    $link = $this->createMock(LinkItemInterface::class);
+    $link->expects($this->any())
+      ->method('getUrl')
+      ->willThrowException(new \InvalidArgumentException());
+
+    $context = $this->createMock(ExecutionContextInterface::class);
+    $context->expects($this->never())
+      ->method('addViolation');
+
+    $this->validate($link, $context);
+  }
+
+  /**
+   * Validate the link.
+   */
+  protected function validate(LinkItemInterface&MockObject $link, ExecutionContextInterface&MockObject $context): void {
+    $validator = new LinkNotExistingInternalConstraintValidator();
+    $validator->initialize($context);
+    $validator->validate($link, new LinkNotExistingInternalConstraint());
+  }
+
+}

core/modules/link/tests/src/Unit/Plugin/migrate/field/d6/LinkFieldTest.php

@@ -0,0 +1,63 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\link\Unit\Plugin\migrate\field\d6;
+
+use Drupal\migrate\Plugin\MigrationInterface;
+use Drupal\Tests\UnitTestCase;
+use Drupal\link\Plugin\migrate\field\d6\LinkField;
+use Prophecy\Argument;
+
+/**
+ * @coversDefaultClass \Drupal\link\Plugin\migrate\field\d6\LinkField
+ * @group link
+ */
+class LinkFieldTest extends UnitTestCase {
+
+  /**
+   * @var \Drupal\migrate_drupal\Plugin\MigrateFieldInterface
+   */
+  protected $plugin;
+
+  /**
+   * @var \Drupal\migrate\Plugin\MigrationInterface
+   */
+  protected $migration;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    $this->plugin = new LinkField([], 'link', []);
+
+    $migration = $this->prophesize(MigrationInterface::class);
+
+    // The plugin's defineValueProcessPipeline() method will call
+    // mergeProcessOfProperty() and return nothing. So, in order to examine the
+    // process pipeline created by the plugin, we need to ensure that
+    // getProcess() always returns the last input to mergeProcessOfProperty().
+    $migration->mergeProcessOfProperty(Argument::type('string'), Argument::type('array'))
+      ->will(function ($arguments) use ($migration) {
+        $migration->getProcess()->willReturn($arguments[1]);
+      });
+
+    $this->migration = $migration->reveal();
+  }
+
+  /**
+   * @covers ::defineValueProcessPipeline
+   */
+  public function testDefineValueProcessPipeline($method = 'defineValueProcessPipeline'): void {
+    $this->plugin->$method($this->migration, 'field_name', []);
+
+    $expected = [
+      'plugin' => 'field_link',
+      'source' => 'field_name',
+    ];
+    $this->assertSame($expected, $this->migration->getProcess());
+  }
+
+}

core/modules/link/tests/src/Unit/Plugin/migrate/process/FieldLinkTest.php

@@ -0,0 +1,133 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\link\Unit\Plugin\migrate\process;
+
+use Drupal\link\Plugin\migrate\process\FieldLink;
+use Drupal\migrate\MigrateExecutableInterface;
+use Drupal\migrate\Plugin\MigrationInterface;
+use Drupal\migrate\Row;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * @group Link
+ */
+class FieldLinkTest extends UnitTestCase {
+
+  /**
+   * Tests the URL transformations in the FieldLink process plugin.
+   *
+   * @dataProvider canonicalizeUriDataProvider
+   */
+  public function testCanonicalizeUri($url, $expected, $configuration = []): void {
+    $link_plugin = new FieldLink($configuration, '', [], $this->createMock(MigrationInterface::class));
+    $transformed = $link_plugin->transform([
+      'url' => $url,
+      'title' => '',
+      'attributes' => serialize([]),
+    ], $this->createMock(MigrateExecutableInterface::class), $this->getMockBuilder(Row::class)->disableOriginalConstructor()->getMock(), NULL);
+    $this->assertEquals($expected, $transformed['uri']);
+  }
+
+  /**
+   * Data provider for testCanonicalizeUri.
+   */
+  public static function canonicalizeUriDataProvider() {
+    return [
+      'Simple front-page' => [
+        '<front>',
+        'internal:/',
+      ],
+      'Front page with query' => [
+        '<front>?query=1',
+        'internal:/?query=1',
+      ],
+      'No leading forward slash' => [
+        'node/10',
+        'internal:/node/10',
+      ],
+      'Leading forward slash' => [
+        '/node/10',
+        'internal:/node/10',
+      ],
+      'Existing scheme' => [
+        'scheme:test',
+        'scheme:test',
+      ],
+      'Absolute URL with protocol prefix' => [
+        'http://www.google.com',
+        'http://www.google.com',
+      ],
+      'Absolute URL without protocol prefix' => [
+        'www.yahoo.com',
+        'http://www.yahoo.com',
+      ],
+      'Absolute URL without protocol prefix nor www' => [
+        'yahoo.com',
+        'https://yahoo.com',
+        ['uri_scheme' => 'https://'],
+      ],
+      'Absolute URL without explicit protocol (protocol-relative)' => [
+        '//example.com',
+        'http://example.com',
+      ],
+      'Absolute URL with non-standard characters' => [
+        'http://www.ßÀÑÐ¥ƒå¢ë.com',
+        'http://www.ßÀÑÐ¥ƒå¢ë.com',
+      ],
+      'Absolute URL with non-standard characters, without protocol prefix' => [
+        'www.ÐØÑ¢åþë.com',
+        'http://www.ÐØÑ¢åþë.com',
+      ],
+      'Absolute URL with non-standard top level domain' => [
+        'http://www.example.xxx',
+        'http://www.example.xxx',
+      ],
+      'Internal link with fragment' => [
+        '/node/10#top',
+        'internal:/node/10#top',
+      ],
+      'External link with fragment' => [
+        'http://www.example.com/page#links',
+        'http://www.example.com/page#links',
+      ],
+      'empty' => [
+        '',
+        'route:<nolink>',
+      ],
+      'No link' => [
+        '<nolink>',
+        'route:<nolink>',
+      ],
+      'none' => [
+        '<none>',
+        'route:<nolink>',
+      ],
+    ];
+  }
+
+  /**
+   * Tests the attributes that are deeply serialized are discarded.
+   */
+  public function testCanonicalizeUriSerialized(): void {
+    $link_plugin = new FieldLink([], '', [], $this->createMock(MigrationInterface::class));
+    $migrate_executable = $this->createMock(MigrateExecutableInterface::class);
+    $row = new Row();
+
+    $transformed = $link_plugin->transform([
+      'url' => '',
+      'title' => '',
+      'attributes' => serialize(serialize(['not too deep'])),
+    ], $migrate_executable, $row, NULL);
+    $this->assertEquals(['not too deep'], $transformed['options']['attributes']);
+
+    $transformed = $link_plugin->transform([
+      'url' => '',
+      'title' => '',
+      'attributes' => serialize(serialize(serialize(['too deep']))),
+    ], $migrate_executable, $row, NULL);
+    $this->assertEmpty($transformed['options']['attributes']);
+  }
+
+}

core/modules/link/tests/themes/link_test_theme/link_test_theme.info.yml

@@ -0,0 +1,10 @@
+name: 'Link Test Theme'
+type: theme
+description: 'Theme for testing link module'
+# version: VERSION
+base theme: stark
+
+# Information added by Drupal.org packaging script on 2024-07-04
+version: '10.3.1'
+project: 'drupal'
+datestamp: 1720094222

core/modules/link/tests/themes/link_test_theme/templates/link-formatter-link-separate.html.twig

@@ -0,0 +1,22 @@
+{#
+/**
+ * @file
+ * Theme override of a link with separate title and URL elements.
+ *
+ * Available variables:
+ * - link: The link that has already been formatted by l().
+ * - title: (optional) A descriptive or alternate title for the link, which may
+ *   be different than the actual link text.
+ *
+ * @see template_preprocess()
+ * @see template_preprocess_link_formatter_link_separate()
+ */
+#}
+{% apply spaceless %}
+  <div class="link-item">
+    {% if title %}
+      <div class="link-title">{{ title }}</div>
+    {% endif %}
+    <div class="link-url">{{ link }}</div>
+  </div>
+{% endapply %}