Issue #2311679 by kim.pepper, mondrake, bhanu951, arla, alexpott, ParisLiakos, yogeshmpawar, pcambra, godotislate, mfb, berdir: Separate MIME type mapping from ExtensionMimeTypeGuesser

24 files changed, 1796 insertions, 190 deletions

diff --git a/core/.phpstan-baseline.php b/core/.phpstan-baseline.php
index 0abeb6f41cb..6f4a52139f1 100644
--- a/core/.phpstan-baseline.php
+++ b/core/.phpstan-baseline.php
@@ -7430,18 +7430,6 @@ $ignoreErrors[] = [
 	'path' => __DIR__ . '/lib/Drupal/Core/File/HtaccessWriterInterface.php',
 ];
 $ignoreErrors[] = [
-	'message' => '#^Method Drupal\\\\Core\\\\File\\\\MimeType\\\\ExtensionMimeTypeGuesser\\:\\:setMapping\\(\\) has no return type specified\\.$#',
-	'identifier' => 'missingType.return',
-	'count' => 1,
-	'path' => __DIR__ . '/lib/Drupal/Core/File/MimeType/ExtensionMimeTypeGuesser.php',
-];
-$ignoreErrors[] = [
-	'message' => '#^Method Drupal\\\\Core\\\\File\\\\MimeType\\\\MimeTypeGuesser\\:\\:registerWithSymfonyGuesser\\(\\) has no return type specified\\.$#',
-	'identifier' => 'missingType.return',
-	'count' => 1,
-	'path' => __DIR__ . '/lib/Drupal/Core/File/MimeType/MimeTypeGuesser.php',
-];
-$ignoreErrors[] = [
 	'message' => '#^Method Drupal\\\\Core\\\\FileTransfer\\\\ChmodInterface\\:\\:chmodJailed\\(\\) has no return type specified\\.$#',
 	'identifier' => 'missingType.return',
 	'count' => 1,
@@ -9400,12 +9388,6 @@ $ignoreErrors[] = [
 	'path' => __DIR__ . '/lib/Drupal/Core/ProxyClass/Extension/ModuleInstaller.php',
 ];
 $ignoreErrors[] = [
-	'message' => '#^Method Drupal\\\\Core\\\\ProxyClass\\\\File\\\\MimeType\\\\ExtensionMimeTypeGuesser\\:\\:setMapping\\(\\) has no return type specified\\.$#',
-	'identifier' => 'missingType.return',
-	'count' => 1,
-	'path' => __DIR__ . '/lib/Drupal/Core/ProxyClass/File/MimeType/ExtensionMimeTypeGuesser.php',
-];
-$ignoreErrors[] = [
 	'message' => '#^Method Drupal\\\\Core\\\\ProxyClass\\\\File\\\\MimeType\\\\MimeTypeGuesser\\:\\:addMimeTypeGuesser\\(\\) has no return type specified\\.$#',
 	'identifier' => 'missingType.return',
 	'count' => 1,
diff --git a/core/core.services.yml b/core/core.services.yml
index bec73aa5ccf..4372e6512c3 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -1805,10 +1805,17 @@ services:
     lazy: true
   file.mime_type.guesser.extension:
     class: Drupal\Core\File\MimeType\ExtensionMimeTypeGuesser
-    arguments: ['@module_handler']
+    arguments: ['@Drupal\Core\File\MimeType\MimeTypeMapInterface', '@file_system']
     tags:
       - { name: mime_type_guesser }
     lazy: true
+  Drupal\Core\File\MimeType\MimeTypeMapFactory:
+    autowire: true
+    public: false
+  Drupal\Core\File\MimeType\MimeTypeMapInterface:
+    factory: ['@Drupal\Core\File\MimeType\MimeTypeMapFactory', create]
+  Drupal\Core\File\EventSubscriber\LegacyMimeTypeMapLoadedSubscriber:
+    autowire: true
   # Currently needs to be public as it is called by
   # \Drupal\Core\Render\Element\StatusMessages.
   # @todo Consider making this service private again after
diff --git a/core/lib/Drupal/Core/File/Event/MimeTypeMapLoadedEvent.php b/core/lib/Drupal/Core/File/Event/MimeTypeMapLoadedEvent.php
new file mode 100644
index 00000000000..8d7ea48630d
--- /dev/null
+++ b/core/lib/Drupal/Core/File/Event/MimeTypeMapLoadedEvent.php
@@ -0,0 +1,19 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Core\File\Event;
+
+use Drupal\Core\File\MimeType\MimeTypeMapInterface;
+use Symfony\Contracts\EventDispatcher\Event;
+
+/**
+ * Event that is fired when the MIME type map is loaded.
+ */
+final class MimeTypeMapLoadedEvent extends Event {
+
+  public function __construct(
+    public readonly MimeTypeMapInterface $map,
+  ) {}
+
+}
diff --git a/core/lib/Drupal/Core/File/EventSubscriber/LegacyMimeTypeMapLoadedSubscriber.php b/core/lib/Drupal/Core/File/EventSubscriber/LegacyMimeTypeMapLoadedSubscriber.php
new file mode 100644
index 00000000000..942cc65f709
--- /dev/null
+++ b/core/lib/Drupal/Core/File/EventSubscriber/LegacyMimeTypeMapLoadedSubscriber.php
@@ -0,0 +1,56 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Core\File\EventSubscriber;
+
+use Drupal\Core\Extension\ModuleHandlerInterface;
+use Drupal\Core\File\Event\MimeTypeMapLoadedEvent;
+use Drupal\Core\File\MimeType\MimeTypeMap;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+
+/**
+ * Modifies the MIME type map by calling hook_file_mimetype_mapping_alter().
+ *
+ * This event subscriber provides BC support for the deprecated
+ * hook_file_mimetype_mapping_alter() and will be removed in drupal:12.0.0.
+ *
+ * @internal
+ *
+ * @see https://www.drupal.org/node/3494040
+ */
+final class LegacyMimeTypeMapLoadedSubscriber implements
+  EventSubscriberInterface {
+
+  public function __construct(
+    protected readonly ModuleHandlerInterface $moduleHandler,
+  ) {}
+
+  /**
+   * Handle the event by calling deprecated hook_file_mimetype_mapping_alter().
+   */
+  public function onMimeTypeMapLoaded(MimeTypeMapLoadedEvent $event): void {
+    if (!$event->map instanceof MimeTypeMap) {
+      return;
+    }
+    // @phpstan-ignore-next-line method.deprecated
+    $mapping = $event->map->getMapping();
+    $this->moduleHandler->alterDeprecated(
+      'This hook is deprecated in drupal:11.2.0 and is removed from drupal:12.0.0. Implement a \Drupal\Core\File\Event\MimeTypeMapLoadedEvent listener instead. See https://www.drupal.org/node/3494040',
+      'file_mimetype_mapping',
+      $mapping,
+    );
+    // @phpstan-ignore-next-line method.deprecated
+    $event->map->setMapping($mapping);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getSubscribedEvents(): array {
+    return [
+      MimeTypeMapLoadedEvent::class => 'onMimeTypeMapLoaded',
+    ];
+  }
+
+}
diff --git a/core/lib/Drupal/Core/File/MimeType/ExtensionMimeTypeGuesser.php b/core/lib/Drupal/Core/File/MimeType/ExtensionMimeTypeGuesser.php
index 4ed1bb82d7d..066bee922b4 100644
--- a/core/lib/Drupal/Core/File/MimeType/ExtensionMimeTypeGuesser.php
+++ b/core/lib/Drupal/Core/File/MimeType/ExtensionMimeTypeGuesser.php
@@ -2,19 +2,28 @@
 
 namespace Drupal\Core\File\MimeType;
 
+use Drupal\Core\DependencyInjection\DeprecatedServicePropertyTrait;
 use Drupal\Core\Extension\ModuleHandlerInterface;
+use Drupal\Core\File\Event\MimeTypeMapLoadedEvent;
+use Drupal\Core\File\FileSystemInterface;
 use Symfony\Component\Mime\MimeTypeGuesserInterface;
 
 /**
  * Makes possible to guess the MIME type of a file using its extension.
  */
 class ExtensionMimeTypeGuesser implements MimeTypeGuesserInterface {
+  use DeprecatedServicePropertyTrait;
 
   /**
    * Default MIME extension mapping.
    *
    * @var array
    *   Array of mimetypes correlated to the extensions that relate to them.
+   *
+   * @deprecated in drupal:11.2.0 and is removed from drupal:12.0.0. Pass a
+   *   MimeTypeMapInterface $map to the constructor instead.
+   *
+   * @see https://www.drupal.org/node/3494040
    */
   protected $defaultMapping = [
     // cspell:disable
@@ -877,39 +886,86 @@ class ExtensionMimeTypeGuesser implements MimeTypeGuesserInterface {
    * The MIME types mapping array after going through the module handler.
    *
    * @var array
+   *
+   * @deprecated in drupal:11.2.0 and is removed from drupal:12.0.0. Pass a
+   *   MimeTypeMapInterface $map to the constructor instead.
+   *
+   * @see https://www.drupal.org/node/3494040
    */
   protected $mapping;
 
   /**
-   * The module handler.
+   * Deprecated service properties.
+   *
+   * @var string[]
    *
-   * @var \Drupal\Core\Extension\ModuleHandlerInterface
+   * @see https://www.drupal.org/node/3494040
    */
-  protected $moduleHandler;
+  protected $deprecatedProperties = [
+    'moduleHandler' => 'module_handler',
+  ];
+
+  /**
+   * The MIME type map.
+   */
+  protected MimeTypeMapInterface $map;
+
+  /**
+   * The file system.
+   */
+  protected FileSystemInterface $fileSystem;
 
   /**
    * Constructs a new ExtensionMimeTypeGuesser.
    *
-   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
-   *   The module handler.
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface|\Drupal\Core\File\MimeType\MimeTypeMapInterface $map
+   *   The MIME type map.
+   * @param \Drupal\Core\File\FileSystemInterface|null $fileSystem
+   *   The file system.
    */
-  public function __construct(ModuleHandlerInterface $module_handler) {
-    $this->moduleHandler = $module_handler;
+  public function __construct(
+    MimeTypeMapInterface|ModuleHandlerInterface $map,
+    ?FileSystemInterface $fileSystem = NULL,
+  ) {
+    if ($map instanceof ModuleHandlerInterface) {
+      @trigger_error(
+        'Calling ' . __METHOD__ . '() with the $map argument as an instance of \Drupal\Core\Extension\ModuleHandlerInterface is deprecated in drupal:11.2.0 and an instance of \Drupal\Core\File\MimeType\MimeTypeMapInterface is required in drupal:12.0.0. See https://www.drupal.org/node/3494040',
+        E_USER_DEPRECATED
+      );
+      $map = \Drupal::service(MimeTypeMapInterface::class);
+    }
+    $this->map = $map;
+    if (!$fileSystem) {
+      @trigger_error(
+        'Calling ' . __METHOD__ . '() without the $fileSystem argument is deprecated in drupal:11.2.0 and is required in drupal:12.0.0. See https://www.drupal.org/node/3494040',
+        E_USER_DEPRECATED
+      );
+      $fileSystem = \Drupal::service(FileSystemInterface::class);
+    }
+    $this->fileSystem = $fileSystem;
   }
 
   /**
    * {@inheritdoc}
    */
   public function guessMimeType($path): ?string {
-    if ($this->mapping === NULL) {
-      $mapping = $this->defaultMapping;
-      // Allow modules to alter the default mapping.
-      $this->moduleHandler->alter('file_mimetype_mapping', $mapping);
-      $this->mapping = $mapping;
+    if (!isset($this->fileSystem)) {
+      @trigger_error(
+        'Calling ' . __METHOD__ . '() without the file_system service already injected is deprecated in drupal:11.2.0 and throws an exception in drupal:12.0.0. See https://www.drupal.org/node/3494040',
+        E_USER_DEPRECATED
+      );
+      $this->fileSystem = \Drupal::service(FileSystemInterface::class);
+    }
+    if (!isset($this->map)) {
+      @trigger_error(
+        'Calling ' . __METHOD__ . '() without the MimeTypeMapInterface service already injected is deprecated in drupal:11.2.0 and throws an exception in drupal:12.0.0. See https://www.drupal.org/node/3494040',
+        E_USER_DEPRECATED
+      );
+      $this->map = \Drupal::service(MimeTypeMapInterface::class);
     }
 
     $extension = '';
-    $file_parts = explode('.', \Drupal::service('file_system')->basename($path));
+    $file_parts = explode('.', $this->fileSystem->basename($path));
 
     // Remove the first part: a full filename should not match an extension,
     // then iterate over the file parts, trying to find a match.
@@ -919,8 +975,8 @@ class ExtensionMimeTypeGuesser implements MimeTypeGuesserInterface {
     // empty.
     while (array_shift($file_parts) !== NULL) {
       $extension = strtolower(implode('.', $file_parts));
-      if (isset($this->mapping['extensions'][$extension])) {
-        return $this->mapping['mimetypes'][$this->mapping['extensions'][$extension]];
+      if ($mimeType = $this->map->getMimeTypeForExtension($extension)) {
+        return $mimeType;
       }
     }
 
@@ -932,9 +988,32 @@ class ExtensionMimeTypeGuesser implements MimeTypeGuesserInterface {
    *
    * @param array|null $mapping
    *   Passing a NULL mapping will cause guess() to use self::$defaultMapping.
+   *
+   * @deprecated in drupal:11.2.0 and is removed from drupal:12.0.0. Use
+   *   \Drupal\Core\File\MimeType\MimeTypeMapInterface::addMapping() instead.
+   *
+   * @see https://www.drupal.org/node/3494040
    */
-  public function setMapping(?array $mapping = NULL) {
-    $this->mapping = $mapping;
+  public function setMapping(?array $mapping = NULL): void {
+    @trigger_error(
+      __METHOD__ . '() is deprecated in drupal:11.2.0 and is removed from drupal:12.0.0. Use \Drupal\Core\File\MimeType\MimeTypeMapInterface::addMapping() instead or define your own MimeTypeMapInterface implementation. See https://www.drupal.org/node/3494040',
+      E_USER_DEPRECATED
+    );
+    // Convert the mapping to be keyed by type.
+    $typeMapping = [];
+    foreach ($mapping['mimetypes'] as $index => $mimetype) {
+      $typeMapping[$mimetype] = array_keys($mapping['extensions'], $index);
+    }
+
+    $this->map = new MimeTypeMap();
+    foreach ($typeMapping as $type => $extensions) {
+      foreach ($extensions as $extension) {
+        $this->map->addMapping($type, $extension);
+      }
+    }
+    \Drupal::service('event_dispatcher')->dispatch(
+      new MimeTypeMapLoadedEvent($this->map)
+    );
   }
 
   /**
diff --git a/core/lib/Drupal/Core/File/MimeType/MimeTypeGuesser.php b/core/lib/Drupal/Core/File/MimeType/MimeTypeGuesser.php
index d1ec980d68b..3a121c1146c 100644
--- a/core/lib/Drupal/Core/File/MimeType/MimeTypeGuesser.php
+++ b/core/lib/Drupal/Core/File/MimeType/MimeTypeGuesser.php
@@ -122,7 +122,9 @@ class MimeTypeGuesser implements MimeTypeGuesserInterface {
    *
    * @see \Symfony\Component\Mime\MimeTypes
    */
-  public static function registerWithSymfonyGuesser(ContainerInterface $container) {
+  public static function registerWithSymfonyGuesser(
+    ContainerInterface $container,
+  ): void {
     $guesser = new MimeTypes();
     $guesser->registerGuesser($container->get('file.mime_type.guesser'));
     MimeTypes::setDefault($guesser);
diff --git a/core/lib/Drupal/Core/File/MimeType/MimeTypeMap.php b/core/lib/Drupal/Core/File/MimeType/MimeTypeMap.php
new file mode 100644
index 00000000000..1a1203241fa
--- /dev/null
+++ b/core/lib/Drupal/Core/File/MimeType/MimeTypeMap.php
@@ -0,0 +1,1018 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Core\File\MimeType;
+
+/**
+ * Provides a sensible mapping between filename extensions and MIME types.
+ */
+class MimeTypeMap implements MimeTypeMapInterface {
+
+  /**
+   * The MIME extension mapping.
+   *
+   * @var array{'mimetypes': array{int,string}, 'extensions': array{string,int}}
+   *   An array consisting of two arrays:
+   *     - mimetypes: MIME types, keyed by a unique number.
+   *     - extensions: an associative array with the MIME type key numbers as
+   *       values. The keys are file extensions, in lower case and without any
+   *       preceding dot.
+   *
+   * cspell:disable.
+   */
+  protected array $mapping = [
+    'mimetypes' => [
+      0 => 'application/andrew-inset',
+      1 => 'application/atom',
+      2 => 'application/atomcat+xml',
+      3 => 'application/atomserv+xml',
+      4 => 'application/cap',
+      5 => 'application/cu-seeme',
+      6 => 'application/dsptype',
+      350 => 'application/epub+zip',
+      359 => 'application/gzip',
+      7 => 'application/hta',
+      8 => 'application/java-archive',
+      9 => 'application/java-serialized-object',
+      10 => 'application/java-vm',
+      11 => 'application/mac-binhex40',
+      12 => 'application/mathematica',
+      13 => 'application/msaccess',
+      14 => 'application/msword',
+      15 => 'application/octet-stream',
+      16 => 'application/oda',
+      17 => 'application/ogg',
+      18 => 'application/pdf',
+      19 => 'application/pgp-keys',
+      20 => 'application/pgp-signature',
+      21 => 'application/pics-rules',
+      22 => 'application/postscript',
+      23 => 'application/rar',
+      24 => 'application/rdf+xml',
+      25 => 'application/rss+xml',
+      26 => 'application/rtf',
+      27 => 'application/smil',
+      349 => 'application/vnd.amazon.ebook',
+      28 => 'application/vnd.cinderella',
+      29 => 'application/vnd.google-earth.kml+xml',
+      30 => 'application/vnd.google-earth.kmz',
+      31 => 'application/vnd.mozilla.xul+xml',
+      32 => 'application/vnd.ms-excel',
+      33 => 'application/vnd.ms-excel.addin.macroEnabled.12',
+      34 => 'application/vnd.ms-excel.sheet.binary.macroEnabled.12',
+      35 => 'application/vnd.ms-excel.sheet.macroEnabled.12',
+      36 => 'application/vnd.ms-excel.template.macroEnabled.12',
+      37 => 'application/vnd.ms-pki.seccat',
+      38 => 'application/vnd.ms-pki.stl',
+      39 => 'application/vnd.ms-powerpoint',
+      40 => 'application/vnd.ms-powerpoint.addin.macroEnabled.12',
+      41 => 'application/vnd.ms-powerpoint.presentation.macroEnabled.12',
+      42 => 'application/vnd.ms-powerpoint.slideshow.macroEnabled.12',
+      43 => 'application/vnd.ms-powerpoint.template.macroEnabled.12',
+      44 => 'application/vnd.ms-word.document.macroEnabled.12',
+      45 => 'application/vnd.ms-word.template.macroEnabled.12',
+      46 => 'application/vnd.ms-xpsdocument',
+      47 => 'application/vnd.oasis.opendocument.chart',
+      48 => 'application/vnd.oasis.opendocument.database',
+      49 => 'application/vnd.oasis.opendocument.formula',
+      50 => 'application/vnd.oasis.opendocument.graphics',
+      51 => 'application/vnd.oasis.opendocument.graphics-template',
+      52 => 'application/vnd.oasis.opendocument.image',
+      53 => 'application/vnd.oasis.opendocument.presentation',
+      54 => 'application/vnd.oasis.opendocument.presentation-template',
+      55 => 'application/vnd.oasis.opendocument.spreadsheet',
+      56 => 'application/vnd.oasis.opendocument.spreadsheet-template',
+      57 => 'application/vnd.oasis.opendocument.text',
+      58 => 'application/vnd.oasis.opendocument.text-master',
+      59 => 'application/vnd.oasis.opendocument.text-template',
+      60 => 'application/vnd.oasis.opendocument.text-web',
+      61 => 'application/vnd.openxmlformats-officedocument.presentationml.presentation',
+      62 => 'application/vnd.openxmlformats-officedocument.presentationml.slideshow',
+      63 => 'application/vnd.openxmlformats-officedocument.presentationml.template',
+      64 => 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
+      65 => 'application/vnd.openxmlformats-officedocument.spreadsheetml.template',
+      66 => 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
+      67 => 'application/vnd.openxmlformats-officedocument.wordprocessingml.template',
+      68 => 'application/vnd.rim.cod',
+      69 => 'application/vnd.smaf',
+      70 => 'application/vnd.stardivision.calc',
+      71 => 'application/vnd.stardivision.chart',
+      72 => 'application/vnd.stardivision.draw',
+      73 => 'application/vnd.stardivision.impress',
+      74 => 'application/vnd.stardivision.math',
+      75 => 'application/vnd.stardivision.writer',
+      76 => 'application/vnd.stardivision.writer-global',
+      77 => 'application/vnd.sun.xml.calc',
+      78 => 'application/vnd.sun.xml.calc.template',
+      79 => 'application/vnd.sun.xml.draw',
+      80 => 'application/vnd.sun.xml.draw.template',
+      81 => 'application/vnd.sun.xml.impress',
+      82 => 'application/vnd.sun.xml.impress.template',
+      83 => 'application/vnd.sun.xml.math',
+      84 => 'application/vnd.sun.xml.writer',
+      85 => 'application/vnd.sun.xml.writer.global',
+      86 => 'application/vnd.sun.xml.writer.template',
+      87 => 'application/vnd.symbian.install',
+      88 => 'application/vnd.visio',
+      89 => 'application/vnd.wap.wbxml',
+      90 => 'application/vnd.wap.wmlc',
+      91 => 'application/vnd.wap.wmlscriptc',
+      92 => 'application/wordperfect',
+      93 => 'application/wordperfect5.1',
+      94 => 'application/x-123',
+      95 => 'application/x-7z-compressed',
+      96 => 'application/x-abiword',
+      97 => 'application/x-apple-diskimage',
+      98 => 'application/x-bcpio',
+      99 => 'application/x-bittorrent',
+      100 => 'application/x-cab',
+      101 => 'application/x-cbr',
+      102 => 'application/x-cbz',
+      103 => 'application/x-cdf',
+      104 => 'application/x-cdlink',
+      105 => 'application/x-chess-pgn',
+      106 => 'application/x-cpio',
+      107 => 'application/x-debian-package',
+      108 => 'application/x-director',
+      109 => 'application/x-dms',
+      110 => 'application/x-doom',
+      111 => 'application/x-dvi',
+      113 => 'application/x-font',
+      114 => 'application/x-freemind',
+      115 => 'application/x-futuresplash',
+      116 => 'application/x-gnumeric',
+      117 => 'application/x-go-sgf',
+      118 => 'application/x-graphing-calculator',
+      119 => 'application/x-gtar',
+      120 => 'application/x-hdf',
+      121 => 'application/x-httpd-eruby',
+      122 => 'application/x-httpd-php',
+      123 => 'application/x-httpd-php-source',
+      124 => 'application/x-httpd-php3',
+      125 => 'application/x-httpd-php3-preprocessed',
+      126 => 'application/x-httpd-php4',
+      127 => 'application/x-ica',
+      128 => 'application/x-internet-signup',
+      129 => 'application/x-iphone',
+      130 => 'application/x-iso9660-image',
+      131 => 'application/x-java-jnlp-file',
+      // Per RFC 9239, text/javascript is preferred over application/javascript.
+      // @see https://www.rfc-editor.org/rfc/rfc9239
+      132 => 'text/javascript',
+      133 => 'application/x-jmol',
+      134 => 'application/x-kchart',
+      135 => 'application/x-killustrator',
+      136 => 'application/x-koan',
+      137 => 'application/x-kpresenter',
+      138 => 'application/x-kspread',
+      139 => 'application/x-kword',
+      140 => 'application/x-latex',
+      141 => 'application/x-lha',
+      142 => 'application/x-lyx',
+      143 => 'application/x-lzh',
+      144 => 'application/x-lzx',
+      145 => 'application/x-maker',
+      146 => 'application/x-mif',
+      351 => 'application/x-mobipocket-ebook',
+      352 => 'application/x-mobipocket-ebook',
+      147 => 'application/x-ms-wmd',
+      148 => 'application/x-ms-wmz',
+      149 => 'application/x-msdos-program',
+      150 => 'application/x-msi',
+      151 => 'application/x-netcdf',
+      152 => 'application/x-ns-proxy-autoconfig',
+      153 => 'application/x-nwc',
+      154 => 'application/x-object',
+      155 => 'application/x-oz-application',
+      156 => 'application/x-pkcs7-certreqresp',
+      157 => 'application/x-pkcs7-crl',
+      158 => 'application/x-python-code',
+      159 => 'application/x-quicktimeplayer',
+      160 => 'application/x-redhat-package-manager',
+      161 => 'application/x-shar',
+      162 => 'application/x-shockwave-flash',
+      163 => 'application/x-stuffit',
+      164 => 'application/x-sv4cpio',
+      165 => 'application/x-sv4crc',
+      166 => 'application/x-tar',
+      167 => 'application/x-tcl',
+      168 => 'application/x-tex-gf',
+      169 => 'application/x-tex-pk',
+      170 => 'application/x-texinfo',
+      171 => 'application/x-trash',
+      172 => 'application/x-troff',
+      173 => 'application/x-troff-man',
+      174 => 'application/x-troff-me',
+      175 => 'application/x-troff-ms',
+      176 => 'application/x-ustar',
+      177 => 'application/x-wais-source',
+      178 => 'application/x-wingz',
+      179 => 'application/x-x509-ca-cert',
+      180 => 'application/x-xcf',
+      181 => 'application/x-xfig',
+      182 => 'application/x-xpinstall',
+      183 => 'application/xhtml+xml',
+      184 => 'application/xml',
+      185 => 'application/zip',
+      360 => 'audio/aac',
+      186 => 'audio/basic',
+      112 => 'audio/flac',
+      187 => 'audio/midi',
+      346 => 'audio/mp4',
+      188 => 'audio/mpeg',
+      189 => 'audio/ogg',
+      190 => 'audio/prs.sid',
+      356 => 'audio/webm',
+      191 => 'audio/x-aiff',
+      192 => 'audio/x-gsm',
+      354 => 'audio/x-matroska',
+      193 => 'audio/x-mpegurl',
+      194 => 'audio/x-ms-wax',
+      195 => 'audio/x-ms-wma',
+      196 => 'audio/x-pn-realaudio',
+      197 => 'audio/x-realaudio',
+      198 => 'audio/x-scpls',
+      199 => 'audio/x-sd2',
+      200 => 'audio/x-wav',
+      201 => 'chemical/x-alchemy',
+      202 => 'chemical/x-cache',
+      203 => 'chemical/x-cache-csf',
+      204 => 'chemical/x-cactvs-binary',
+      205 => 'chemical/x-cdx',
+      206 => 'chemical/x-cerius',
+      207 => 'chemical/x-chem3d',
+      208 => 'chemical/x-chemdraw',
+      209 => 'chemical/x-cif',
+      210 => 'chemical/x-cmdf',
+      211 => 'chemical/x-cml',
+      212 => 'chemical/x-compass',
+      213 => 'chemical/x-crossfire',
+      214 => 'chemical/x-csml',
+      215 => 'chemical/x-ctx',
+      216 => 'chemical/x-cxf',
+      217 => 'chemical/x-embl-dl-nucleotide',
+      218 => 'chemical/x-galactic-spc',
+      219 => 'chemical/x-gamess-input',
+      220 => 'chemical/x-gaussian-checkpoint',
+      221 => 'chemical/x-gaussian-cube',
+      222 => 'chemical/x-gaussian-input',
+      223 => 'chemical/x-gaussian-log',
+      224 => 'chemical/x-gcg8-sequence',
+      225 => 'chemical/x-genbank',
+      226 => 'chemical/x-hin',
+      227 => 'chemical/x-isostar',
+      228 => 'chemical/x-jcamp-dx',
+      229 => 'chemical/x-kinemage',
+      230 => 'chemical/x-macmolecule',
+      231 => 'chemical/x-macromodel-input',
+      232 => 'chemical/x-mdl-molfile',
+      233 => 'chemical/x-mdl-rdfile',
+      234 => 'chemical/x-mdl-rxnfile',
+      235 => 'chemical/x-mdl-sdfile',
+      236 => 'chemical/x-mdl-tgf',
+      237 => 'chemical/x-mmcif',
+      238 => 'chemical/x-mol2',
+      239 => 'chemical/x-molconn-Z',
+      240 => 'chemical/x-mopac-graph',
+      241 => 'chemical/x-mopac-input',
+      242 => 'chemical/x-mopac-out',
+      243 => 'chemical/x-mopac-vib',
+      244 => 'chemical/x-ncbi-asn1-ascii',
+      245 => 'chemical/x-ncbi-asn1-binary',
+      246 => 'chemical/x-ncbi-asn1-spec',
+      247 => 'chemical/x-pdb',
+      248 => 'chemical/x-rosdal',
+      249 => 'chemical/x-swissprot',
+      250 => 'chemical/x-vamas-iso14976',
+      251 => 'chemical/x-vmd',
+      252 => 'chemical/x-xtel',
+      253 => 'chemical/x-xyz',
+      362 => 'image/avif',
+      254 => 'image/gif',
+      255 => 'image/ief',
+      256 => 'image/jpeg',
+      257 => 'image/pcx',
+      258 => 'image/png',
+      259 => 'image/svg+xml',
+      260 => 'image/tiff',
+      261 => 'image/vnd.djvu',
+      262 => 'image/vnd.microsoft.icon',
+      263 => 'image/vnd.wap.wbmp',
+      355 => 'image/webp',
+      264 => 'image/x-cmu-raster',
+      265 => 'image/x-coreldraw',
+      266 => 'image/x-coreldrawpattern',
+      267 => 'image/x-coreldrawtemplate',
+      268 => 'image/x-corelphotopaint',
+      269 => 'image/x-jg',
+      270 => 'image/x-jng',
+      271 => 'image/x-ms-bmp',
+      272 => 'image/x-photoshop',
+      273 => 'image/x-portable-anymap',
+      274 => 'image/x-portable-bitmap',
+      275 => 'image/x-portable-graymap',
+      276 => 'image/x-portable-pixmap',
+      277 => 'image/x-rgb',
+      278 => 'image/x-xbitmap',
+      279 => 'image/x-xpixmap',
+      280 => 'image/x-xwindowdump',
+      281 => 'message/rfc822',
+      282 => 'model/iges',
+      283 => 'model/mesh',
+      284 => 'model/vrml',
+      285 => 'text/calendar',
+      286 => 'text/css',
+      287 => 'text/csv',
+      288 => 'text/h323',
+      289 => 'text/html',
+      290 => 'text/iuls',
+      291 => 'text/mathml',
+      292 => 'text/plain',
+      293 => 'text/richtext',
+      294 => 'text/scriptlet',
+      295 => 'text/tab-separated-values',
+      296 => 'text/texmacs',
+      297 => 'text/vnd.sun.j2me.app-descriptor',
+      298 => 'text/vnd.wap.wml',
+      299 => 'text/vnd.wap.wmlscript',
+      358 => 'text/vtt',
+      300 => 'text/x-bibtex',
+      301 => 'text/x-boo',
+      302 => 'text/x-c++hdr',
+      303 => 'text/x-c++src',
+      304 => 'text/x-chdr',
+      305 => 'text/x-component',
+      306 => 'text/x-csh',
+      307 => 'text/x-csrc',
+      308 => 'text/x-diff',
+      309 => 'text/x-dsrc',
+      310 => 'text/x-haskell',
+      311 => 'text/x-java',
+      312 => 'text/x-literate-haskell',
+      313 => 'text/x-moc',
+      314 => 'text/x-pascal',
+      315 => 'text/x-pcs-gcd',
+      316 => 'text/x-perl',
+      317 => 'text/x-python',
+      318 => 'text/x-setext',
+      319 => 'text/x-sh',
+      320 => 'text/x-tcl',
+      321 => 'text/x-tex',
+      322 => 'text/x-vcalendar',
+      323 => 'text/x-vcard',
+      324 => 'video/3gpp',
+      325 => 'video/dl',
+      326 => 'video/dv',
+      327 => 'video/fli',
+      328 => 'video/gl',
+      329 => 'video/mp4',
+      330 => 'video/mpeg',
+      331 => 'video/ogg',
+      332 => 'video/quicktime',
+      333 => 'video/vnd.mpegurl',
+      357 => 'video/webm',
+      347 => 'video/x-flv',
+      334 => 'video/x-la-asf',
+      348 => 'video/x-m4v',
+      353 => 'video/x-matroska',
+      335 => 'video/x-mng',
+      336 => 'video/x-ms-asf',
+      337 => 'video/x-ms-wm',
+      338 => 'video/x-ms-wmv',
+      339 => 'video/x-ms-wmx',
+      340 => 'video/x-ms-wvx',
+      341 => 'video/x-msvideo',
+      342 => 'video/x-sgi-movie',
+      343 => 'x-conference/x-cooltalk',
+      344 => 'x-epoc/x-sisx-app',
+      345 => 'x-world/x-vrml',
+      361 => 'application/json',
+    ],
+
+    // Extensions added to this list MUST be lower-case.
+    'extensions' => [
+      'ez' => 0,
+      'atom' => 1,
+      'atomcat' => 2,
+      'atomsrv' => 3,
+      'cap' => 4,
+      'pcap' => 4,
+      'cu' => 5,
+      'tsp' => 6,
+      'hta' => 7,
+      'jar' => 8,
+      'ser' => 9,
+      'class' => 10,
+      'hqx' => 11,
+      'nb' => 12,
+      'mdb' => 13,
+      'dot' => 14,
+      'doc' => 14,
+      'bin' => 15,
+      'oda' => 16,
+      'ogx' => 17,
+      'pdf' => 18,
+      'key' => 19,
+      'pgp' => 20,
+      'prf' => 21,
+      'eps' => 22,
+      'ai' => 22,
+      'ps' => 22,
+      'rar' => 23,
+      'rdf' => 24,
+      'rss' => 25,
+      'rtf' => 26,
+      'smi' => 27,
+      'smil' => 27,
+      'cdy' => 28,
+      'kml' => 29,
+      'kmz' => 30,
+      'xul' => 31,
+      'xlb' => 32,
+      'xlt' => 32,
+      'xls' => 32,
+      'xlam' => 33,
+      'xlsb' => 34,
+      'xlsm' => 35,
+      'xltm' => 36,
+      'cat' => 37,
+      'stl' => 38,
+      'pps' => 39,
+      'ppt' => 39,
+      'ppam' => 40,
+      'pptm' => 41,
+      'ppsm' => 42,
+      'potm' => 43,
+      'docm' => 44,
+      'dotm' => 45,
+      'xps' => 46,
+      'odc' => 47,
+      'odb' => 48,
+      'odf' => 49,
+      'odg' => 50,
+      'otg' => 51,
+      'odi' => 52,
+      'odp' => 53,
+      'otp' => 54,
+      'ods' => 55,
+      'ots' => 56,
+      'odt' => 57,
+      'odm' => 58,
+      'ott' => 59,
+      'oth' => 60,
+      'pptx' => 61,
+      'ppsx' => 62,
+      'potx' => 63,
+      'xlsx' => 64,
+      'xltx' => 65,
+      'docx' => 66,
+      'dotx' => 67,
+      'cod' => 68,
+      'mmf' => 69,
+      'sdc' => 70,
+      'sds' => 71,
+      'sda' => 72,
+      'sdd' => 73,
+      'sdw' => 75,
+      'sgl' => 76,
+      'sxc' => 77,
+      'stc' => 78,
+      'sxd' => 79,
+      'std' => 80,
+      'sxi' => 81,
+      'sti' => 82,
+      'sxm' => 83,
+      'sxw' => 84,
+      'sxg' => 85,
+      'stw' => 86,
+      'sis' => 87,
+      'vsd' => 88,
+      'wbxml' => 89,
+      'wmlc' => 90,
+      'wmlsc' => 91,
+      'wpd' => 92,
+      'wp5' => 93,
+      'wk' => 94,
+      '7z' => 95,
+      'abw' => 96,
+      'dmg' => 97,
+      'bcpio' => 98,
+      'torrent' => 99,
+      'cab' => 100,
+      'cbr' => 101,
+      'cbz' => 102,
+      'cdf' => 103,
+      'vcd' => 104,
+      'pgn' => 105,
+      'cpio' => 106,
+      'udeb' => 107,
+      'deb' => 107,
+      'dir' => 108,
+      'dxr' => 108,
+      'dcr' => 108,
+      'dms' => 109,
+      'wad' => 110,
+      'dvi' => 111,
+      'flac' => 112,
+      'pfa' => 113,
+      'pfb' => 113,
+      'pcf' => 113,
+      'gsf' => 113,
+      'pcf.z' => 113,
+      'mm' => 114,
+      'spl' => 115,
+      'gnumeric' => 116,
+      'sgf' => 117,
+      'gcf' => 118,
+      'taz' => 119,
+      'gtar' => 119,
+      'tgz' => 119,
+      'hdf' => 120,
+      'rhtml' => 121,
+      'phtml' => 122,
+      'pht' => 122,
+      'php' => 122,
+      'phps' => 123,
+      'php3' => 124,
+      'php3p' => 125,
+      'php4' => 126,
+      'ica' => 127,
+      'ins' => 128,
+      'isp' => 128,
+      'iii' => 129,
+      'iso' => 130,
+      'jnlp' => 131,
+      'js' => 132,
+      'jmz' => 133,
+      'chrt' => 134,
+      'kil' => 135,
+      'skp' => 136,
+      'skd' => 136,
+      'skm' => 136,
+      'skt' => 136,
+      'kpr' => 137,
+      'kpt' => 137,
+      'ksp' => 138,
+      'kwd' => 139,
+      'kwt' => 139,
+      'latex' => 140,
+      'lha' => 141,
+      'lyx' => 142,
+      'lzh' => 143,
+      'lzx' => 144,
+      'maker' => 145,
+      'frm' => 145,
+      'frame' => 145,
+      'fm' => 145,
+      'book' => 145,
+      'fb' => 145,
+      'fbdoc' => 145,
+      'mif' => 146,
+      'wmd' => 147,
+      'wmz' => 148,
+      'dll' => 149,
+      'bat' => 149,
+      'exe' => 149,
+      'com' => 149,
+      'msi' => 150,
+      'nc' => 151,
+      'pac' => 152,
+      'nwc' => 153,
+      'o' => 154,
+      'oza' => 155,
+      'p7r' => 156,
+      'crl' => 157,
+      'pyo' => 158,
+      'pyc' => 158,
+      'qtl' => 159,
+      'rpm' => 160,
+      'shar' => 161,
+      'swf' => 162,
+      'swfl' => 162,
+      'sitx' => 163,
+      'sit' => 163,
+      'sv4cpio' => 164,
+      'sv4crc' => 165,
+      'tar' => 166,
+      'gf' => 168,
+      'pk' => 169,
+      'texi' => 170,
+      'texinfo' => 170,
+      'sik' => 171,
+      '~' => 171,
+      'bak' => 171,
+      '%' => 171,
+      'old' => 171,
+      't' => 172,
+      'roff' => 172,
+      'tr' => 172,
+      'man' => 173,
+      'me' => 174,
+      'ms' => 175,
+      'ustar' => 176,
+      'src' => 177,
+      'wz' => 178,
+      'crt' => 179,
+      'xcf' => 180,
+      'fig' => 181,
+      'xpi' => 182,
+      'xht' => 183,
+      'xhtml' => 183,
+      'xml' => 184,
+      'xsl' => 184,
+      'zip' => 185,
+      'au' => 186,
+      'snd' => 186,
+      'mid' => 187,
+      'midi' => 187,
+      'kar' => 187,
+      'mpega' => 188,
+      'mpga' => 188,
+      'mp3' => 188,
+      'mp2' => 188,
+      'ogg' => 189,
+      'oga' => 189,
+      'opus' => 189,
+      'spx' => 189,
+      'sid' => 190,
+      'aif' => 191,
+      'aiff' => 191,
+      'aifc' => 191,
+      'gsm' => 192,
+      'm3u' => 193,
+      'wax' => 194,
+      'wma' => 195,
+      'rm' => 196,
+      'ram' => 196,
+      'ra' => 197,
+      'pls' => 198,
+      'sd2' => 199,
+      'wav' => 200,
+      'alc' => 201,
+      'cac' => 202,
+      'cache' => 202,
+      'csf' => 203,
+      'cascii' => 204,
+      'cbin' => 204,
+      'ctab' => 204,
+      'cdx' => 205,
+      'cer' => 206,
+      'c3d' => 207,
+      'chm' => 208,
+      'cif' => 209,
+      'cmdf' => 210,
+      'cml' => 211,
+      'cpa' => 212,
+      'bsd' => 213,
+      'csml' => 214,
+      'csm' => 214,
+      'ctx' => 215,
+      'cxf' => 216,
+      'cef' => 216,
+      'emb' => 217,
+      'embl' => 217,
+      'spc' => 218,
+      'gam' => 219,
+      'inp' => 219,
+      'gamin' => 219,
+      'fchk' => 220,
+      'fch' => 220,
+      'cub' => 221,
+      'gau' => 222,
+      'gjf' => 222,
+      'gjc' => 222,
+      'gal' => 223,
+      'gcg' => 224,
+      'gen' => 225,
+      'hin' => 226,
+      'istr' => 227,
+      'ist' => 227,
+      'dx' => 228,
+      'jdx' => 228,
+      'kin' => 229,
+      'mcm' => 230,
+      'mmd' => 231,
+      'mmod' => 231,
+      'mol' => 232,
+      'rd' => 233,
+      'rxn' => 234,
+      'sdf' => 235,
+      'sd' => 235,
+      'tgf' => 236,
+      'mcif' => 237,
+      'mol2' => 238,
+      'b' => 239,
+      'gpt' => 240,
+      'mopcrt' => 241,
+      'zmt' => 241,
+      'mpc' => 241,
+      'dat' => 241,
+      'mop' => 241,
+      'moo' => 242,
+      'mvb' => 243,
+      'prt' => 244,
+      'aso' => 245,
+      'val' => 245,
+      'asn' => 246,
+      'ent' => 247,
+      'pdb' => 247,
+      'ros' => 248,
+      'sw' => 249,
+      'vms' => 250,
+      'vmd' => 251,
+      'xtel' => 252,
+      'xyz' => 253,
+      'gif' => 254,
+      'ief' => 255,
+      'jpeg' => 256,
+      'jpe' => 256,
+      'jpg' => 256,
+      'pcx' => 257,
+      'png' => 258,
+      'svgz' => 259,
+      'svg' => 259,
+      'tif' => 260,
+      'tiff' => 260,
+      'djvu' => 261,
+      'djv' => 261,
+      'ico' => 262,
+      'wbmp' => 263,
+      'ras' => 264,
+      'cdr' => 265,
+      'pat' => 266,
+      'cdt' => 267,
+      'cpt' => 268,
+      'art' => 269,
+      'jng' => 270,
+      'bmp' => 271,
+      'psd' => 272,
+      'pnm' => 273,
+      'pbm' => 274,
+      'pgm' => 275,
+      'ppm' => 276,
+      'rgb' => 277,
+      'xbm' => 278,
+      'xpm' => 279,
+      'xwd' => 280,
+      'eml' => 281,
+      'igs' => 282,
+      'iges' => 282,
+      'silo' => 283,
+      'msh' => 283,
+      'mesh' => 283,
+      'icz' => 285,
+      'ics' => 285,
+      'css' => 286,
+      'csv' => 287,
+      '323' => 288,
+      'html' => 289,
+      'htm' => 289,
+      'shtml' => 289,
+      'uls' => 290,
+      'mml' => 291,
+      'txt' => 292,
+      'pot' => 292,
+      'text' => 292,
+      'asc' => 292,
+      'rtx' => 293,
+      'wsc' => 294,
+      'sct' => 294,
+      'tsv' => 295,
+      'ts' => 296,
+      'tm' => 296,
+      'jad' => 297,
+      'wml' => 298,
+      'wmls' => 299,
+      'bib' => 300,
+      'boo' => 301,
+      'hpp' => 302,
+      'hh' => 302,
+      'h++' => 302,
+      'hxx' => 302,
+      'cxx' => 303,
+      'cc' => 303,
+      'cpp' => 303,
+      'c++' => 303,
+      'h' => 304,
+      'htc' => 305,
+      'csh' => 306,
+      'c' => 307,
+      'patch' => 308,
+      'diff' => 308,
+      'd' => 309,
+      'hs' => 310,
+      'java' => 311,
+      'lhs' => 312,
+      'moc' => 313,
+      'pas' => 314,
+      'p' => 314,
+      'gcd' => 315,
+      'pm' => 316,
+      'pl' => 316,
+      'py' => 317,
+      'etx' => 318,
+      'sh' => 319,
+      'tk' => 320,
+      'tcl' => 320,
+      'cls' => 321,
+      'ltx' => 321,
+      'sty' => 321,
+      'tex' => 321,
+      'vcs' => 322,
+      'vcf' => 323,
+      '3gp' => 324,
+      'dl' => 325,
+      'dif' => 326,
+      'dv' => 326,
+      'fli' => 327,
+      'gl' => 328,
+      'mp4' => 329,
+      'f4v' => 329,
+      'f4p' => 329,
+      'mpe' => 330,
+      'mpeg' => 330,
+      'mpg' => 330,
+      'ogv' => 331,
+      'qt' => 332,
+      'mov' => 332,
+      'mxu' => 333,
+      'lsf' => 334,
+      'lsx' => 334,
+      'mng' => 335,
+      'asx' => 336,
+      'asf' => 336,
+      'wm' => 337,
+      'wmv' => 338,
+      'wmx' => 339,
+      'wvx' => 340,
+      'avi' => 341,
+      'movie' => 342,
+      'ice' => 343,
+      'sisx' => 344,
+      'wrl' => 345,
+      'vrm' => 345,
+      'vrml' => 345,
+      'f4a' => 346,
+      'f4b' => 346,
+      'm4a' => 346,
+      'flv' => 347,
+      'm4v' => 348,
+      'azw' => 349,
+      'epub' => 350,
+      'mobi' => 351,
+      'prc' => 352,
+      'mkv' => 353,
+      'mka' => 354,
+      'webp' => 355,
+      'weba' => 356,
+      'webm' => 357,
+      'vtt' => 358,
+      'gz' => 359,
+      'mjs' => 132,
+      'aac' => 360,
+      'json' => 361,
+      'avif' => 362,
+    ],
+  ];
+
+  // cspell:enable
+
+  /**
+   * {@inheritdoc}
+   */
+  public function addMapping(string $mimetype, string $extension): static {
+    $mimetype = strtolower($mimetype);
+    $extension = strtolower($extension);
+    $this->mapping['mimetypes'] ??= [];
+    $key = array_search($mimetype, $this->mapping['mimetypes'], TRUE);
+    if ($key === FALSE) {
+      $key = count($this->mapping['mimetypes']);
+      $this->mapping['mimetypes'][] = $mimetype;
+    }
+    $this->mapping['extensions'][$extension] = $key;
+    return $this;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function removeMapping(string $mimetype, string $extension): bool {
+    $extension = strtolower($extension);
+    if (isset($this->mapping['extensions'][$extension])) {
+      unset($this->mapping['extensions'][$extension]);
+      return TRUE;
+    }
+    return FALSE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function removeMimeType(string $mimetype): bool {
+    $mimetype = strtolower($mimetype);
+    $key = array_search($mimetype, $this->mapping['mimetypes'], TRUE);
+    if ($key === FALSE) {
+      return FALSE;
+    }
+    foreach ($this->getExtensionsForMimeType($mimetype) as $extension) {
+      $this->removeMapping($mimetype, $extension);
+    }
+    unset($this->mapping['mimetypes'][$key]);
+    return TRUE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function listMimeTypes(): array {
+    $mimeTypes = array_values($this->mapping['mimetypes']);
+    sort($mimeTypes);
+
+    return $mimeTypes;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function listExtensions(): array {
+    $extensions = array_keys($this->mapping['extensions']);
+    sort($extensions);
+
+    return $extensions;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function hasMimeType(string $mimetype): bool {
+    return in_array(
+      strtolower($mimetype),
+      $this->mapping['mimetypes'],
+      TRUE
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function hasExtension(string $extension): bool {
+    return isset($this->mapping['extensions'][strtolower($extension)]);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getMimeTypeForExtension($extension): ?string {
+    $extension = strtolower($extension);
+    $extensions = $this->mapping['extensions'] ?? [];
+
+    return isset($extensions[$extension]) ? $this->mapping['mimetypes'][$extensions[$extension]] : NULL;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getExtensionsForMimeType($mimetype): array {
+    $mimetype = strtolower($mimetype);
+    $key = array_search($mimetype, $this->mapping['mimetypes'], TRUE);
+    if ($key === FALSE) {
+      return [];
+    }
+    $extensions = array_keys($this->mapping['extensions'], $key, TRUE);
+    sort($extensions);
+    return $extensions;
+  }
+
+  /**
+   * Gets the underlying mapping array.
+   *
+   * @deprecated in drupal:11.2.0 and is removed from drupal:12.0.0. There is no
+   *   replacement for this method.
+   *
+   * @see https://www.drupal.org/node/3494040
+   * @see \Drupal\Core\File\EventSubscriber\LegacyMimeTypeMapLoadedSubscriber
+   */
+  public function getMapping(): array {
+    // We do not trigger a deprecation error as this method is needed for
+    // calling the deprecated hook_file_mimetype_mapping_alter() in
+    // LegacyMimeTypeMapLoadedSubscriber::onMimeTypeMapLoaded().
+    return $this->mapping;
+  }
+
+  /**
+   * Sets the underlying mapping array.
+   *
+   * @deprecated in drupal:11.2.0 and is removed from drupal:12.0.0. There is no
+   *   replacement for this method.
+   *
+   * @see https://www.drupal.org/node/3494040
+   */
+  public function setMapping(array $mapping): void {
+    // We do not trigger a deprecation error as this method is needed for
+    // calling the deprecated hook_file_mimetype_mapping_alter() in
+    // LegacyMimeTypeMapLoadedSubscriber::onMimeTypeMapLoaded().
+    $this->mapping = $mapping;
+  }
+
+}
diff --git a/core/lib/Drupal/Core/File/MimeType/MimeTypeMapFactory.php b/core/lib/Drupal/Core/File/MimeType/MimeTypeMapFactory.php
new file mode 100644
index 00000000000..573a33fec5c
--- /dev/null
+++ b/core/lib/Drupal/Core/File/MimeType/MimeTypeMapFactory.php
@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Core\File\MimeType;
+
+use Drupal\Core\File\Event\MimeTypeMapLoadedEvent;
+use Psr\EventDispatcher\EventDispatcherInterface;
+
+/**
+ * Factory for creating the MIME type map.
+ */
+class MimeTypeMapFactory {
+
+  public function __construct(
+    protected readonly EventDispatcherInterface $eventDispatcher,
+  ) {}
+
+  /**
+   * Creates an instance of the MIME type map.
+   *
+   * @return \Drupal\Core\File\MimeType\MimeTypeMapInterface
+   *   The MIME type map.
+   */
+  public function create(): MimeTypeMapInterface {
+    $map = $this->doCreateMap();
+    $this->eventDispatcher->dispatch(new MimeTypeMapLoadedEvent($map));
+    return $map;
+  }
+
+  protected function doCreateMap(): MimeTypeMapInterface {
+    return new MimeTypeMap();
+  }
+
+}
diff --git a/core/lib/Drupal/Core/File/MimeType/MimeTypeMapInterface.php b/core/lib/Drupal/Core/File/MimeType/MimeTypeMapInterface.php
new file mode 100644
index 00000000000..5483c67d8a1
--- /dev/null
+++ b/core/lib/Drupal/Core/File/MimeType/MimeTypeMapInterface.php
@@ -0,0 +1,108 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Core\File\MimeType;
+
+/**
+ * Provides an interface for MIME type to file extension mapping.
+ */
+interface MimeTypeMapInterface {
+
+  /**
+   * Adds a mapping between a MIME type and an extension.
+   *
+   * @param string $mimetype
+   *   The MIME type the passed extension should map.
+   * @param string $extension
+   *   The extension(s) that should map to the passed MIME type.
+   *
+   * @return $this
+   */
+  public function addMapping(string $mimetype, string $extension): self;
+
+  /**
+   * Removes the mapping between a MIME type and an extension.
+   *
+   * @param string $mimetype
+   *   The MIME type to be removed from the mapping.
+   * @param string $extension
+   *   The extension to be removed from the mapping.
+   *
+   * @return bool
+   *   TRUE if the extension was present, FALSE otherwise.
+   */
+  public function removeMapping(string $mimetype, string $extension): bool;
+
+  /**
+   * Removes a MIME type and all its mapped extensions from the mapping.
+   *
+   * @param string $mimetype
+   *   The MIME type to be removed from the mapping.
+   *
+   * @return bool
+   *   TRUE if the MIME type was present, FALSE otherwise.
+   */
+  public function removeMimeType(string $mimetype): bool;
+
+  /**
+   * Returns known MIME types.
+   *
+   * @return string[]
+   *   An array of MIME types.
+   */
+  public function listMimeTypes(): array;
+
+  /**
+   * Returns known file extensions.
+   *
+   * @return string[]
+   *   An array of file extensions.
+   */
+  public function listExtensions(): array;
+
+  /**
+   * Determines if a MIME type exists.
+   *
+   * @param string $mimetype
+   *   The mime type.
+   *
+   * @return bool
+   *   TRUE if the MIME type exists, FALSE otherwise.
+   */
+  public function hasMimeType(string $mimetype): bool;
+
+  /**
+   * Determines if a file extension exists.
+   *
+   * @param string $extension
+   *   The file extension.
+   *
+   * @return bool
+   *   TRUE if the file extension exists, FALSE otherwise.
+   */
+  public function hasExtension(string $extension): bool;
+
+  /**
+   * Returns the appropriate MIME type for a given file extension.
+   *
+   * @param string $extension
+   *   A file extension, without leading dot.
+   *
+   * @return string|null
+   *   A matching MIME type, or NULL if no MIME type matches the extension.
+   */
+  public function getMimeTypeForExtension(string $extension): ?string;
+
+  /**
+   * Returns the appropriate extensions for a given MIME type.
+   *
+   * @param string $mimetype
+   *   A MIME type.
+   *
+   * @return string[]
+   *   An array of file extensions matching the MIME type, without leading dot.
+   */
+  public function getExtensionsForMimeType(string $mimetype): array;
+
+}
diff --git a/core/lib/Drupal/Core/File/file.api.php b/core/lib/Drupal/Core/File/file.api.php
index 04e6e8a43df..0c18aece9cd 100644
--- a/core/lib/Drupal/Core/File/file.api.php
+++ b/core/lib/Drupal/Core/File/file.api.php
@@ -109,16 +109,19 @@ function hook_file_url_alter(&$uri) {
 /**
  * Alter MIME type mappings used to determine MIME type from a file extension.
  *
- * Invoked by
- * \Drupal\Core\File\MimeType\ExtensionMimeTypeGuesser::guessMimeType(). It is
- * used to allow modules to add to or modify the default mapping from
- * \Drupal\Core\File\MimeType\ExtensionMimeTypeGuesser::$defaultMapping.
- *
  * @param array $mapping
  *   An array of mimetypes correlated to the extensions that relate to them.
  *   The array has 'mimetypes' and 'extensions' elements, each of which is an
  *   array.
  *
+ * @deprecated in drupal:11.2.0 and is removed from drupal:12.0.0. Create a
+ *   \Drupal\Core\File\Event\MimeTypeMapLoadedEvent subscriber instead.
+ *
+ * It is used to allow modules to add to or modify the default mapping of
+ * MIME type to file extensions.
+ *
+ * @see https://www.drupal.org/node/3494040
+ * @see \Drupal\Core\File\EventSubscriber\LegacyMimeTypeMapLoadedSubscriber
  * @see \Drupal\Core\File\MimeType\ExtensionMimeTypeGuesser::guessMimeType()
  * @see \Drupal\Core\File\MimeType\ExtensionMimeTypeGuesser::$defaultMapping
  */
diff --git a/core/lib/Drupal/Core/ProxyClass/File/MimeType/ExtensionMimeTypeGuesser.php b/core/lib/Drupal/Core/ProxyClass/File/MimeType/ExtensionMimeTypeGuesser.php
index 2cb59856a95..a9e4bd55f15 100644
--- a/core/lib/Drupal/Core/ProxyClass/File/MimeType/ExtensionMimeTypeGuesser.php
+++ b/core/lib/Drupal/Core/ProxyClass/File/MimeType/ExtensionMimeTypeGuesser.php
@@ -78,9 +78,9 @@ namespace Drupal\Core\ProxyClass\File\MimeType {
         /**
          * {@inheritdoc}
          */
-        public function setMapping(?array $mapping = NULL)
+        public function setMapping(?array $mapping = NULL): void
         {
-            return $this->lazyLoadItself()->setMapping($mapping);
+            $this->lazyLoadItself()->setMapping($mapping);
         }
 
         /**
diff --git a/core/lib/Drupal/Core/ProxyClass/File/MimeType/MimeTypeGuesser.php b/core/lib/Drupal/Core/ProxyClass/File/MimeType/MimeTypeGuesser.php
index 0a259a396c0..5480214fc1e 100644
--- a/core/lib/Drupal/Core/ProxyClass/File/MimeType/MimeTypeGuesser.php
+++ b/core/lib/Drupal/Core/ProxyClass/File/MimeType/MimeTypeGuesser.php
@@ -91,6 +91,14 @@ namespace Drupal\Core\ProxyClass\File\MimeType {
             return $this->lazyLoadItself()->isGuesserSupported();
         }
 
+        /**
+         * {@inheritdoc}
+         */
+        public static function registerWithSymfonyGuesser(\Symfony\Component\DependencyInjection\ContainerInterface $container): void
+        {
+            \Drupal\Core\File\MimeType\MimeTypeGuesser::registerWithSymfonyGuesser($container);
+        }
+
     }
 
 }
diff --git a/core/modules/file/src/Plugin/Field/FieldFormatter/FileMediaFormatterBase.php b/core/modules/file/src/Plugin/Field/FieldFormatter/FileMediaFormatterBase.php
index 7b749cfbce4..c00f4aeb397 100644
--- a/core/modules/file/src/Plugin/Field/FieldFormatter/FileMediaFormatterBase.php
+++ b/core/modules/file/src/Plugin/Field/FieldFormatter/FileMediaFormatterBase.php
@@ -6,6 +6,7 @@ use Drupal\Core\Cache\Cache;
 use Drupal\Core\Field\EntityReferenceFieldItemListInterface;
 use Drupal\Core\Field\FieldDefinitionInterface;
 use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\File\MimeType\MimeTypeMapInterface;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Template\Attribute;
 
@@ -75,12 +76,12 @@ abstract class FileMediaFormatterBase extends FileFormatterBase implements FileM
     if (!parent::isApplicable($field_definition)) {
       return FALSE;
     }
-    /** @var \Symfony\Component\Mime\MimeTypeGuesserInterface $extension_mime_type_guesser */
-    $extension_mime_type_guesser = \Drupal::service('file.mime_type.guesser.extension');
+    /** @var \Drupal\Core\File\MimeType\MimeTypeMapInterface $mime_type_map */
+    $mime_type_map = \Drupal::service(MimeTypeMapInterface::class);
     $extension_list = array_filter(preg_split('/\s+/', $field_definition->getSetting('file_extensions')));
 
     foreach ($extension_list as $extension) {
-      $mime_type = $extension_mime_type_guesser->guessMimeType('fakedFile.' . $extension);
+      $mime_type = $mime_type_map->getMimeTypeForExtension($extension);
       if ($mime_type !== NULL && static::mimeTypeApplies($mime_type)) {
         return TRUE;
       }
diff --git a/core/modules/file/tests/file_deprecated_test/file_deprecated_test.info.yml b/core/modules/file/tests/file_deprecated_test/file_deprecated_test.info.yml
new file mode 100644
index 00000000000..50907a4f62e
--- /dev/null
+++ b/core/modules/file/tests/file_deprecated_test/file_deprecated_test.info.yml
@@ -0,0 +1,4 @@
+name: 'File deprecation test'
+type: module
+description: 'Support module for testing deprecated file features.'
+package: Testing
diff --git a/core/modules/file/tests/file_deprecated_test/file_deprecated_test.module b/core/modules/file/tests/file_deprecated_test/file_deprecated_test.module
new file mode 100644
index 00000000000..625f5ee9dbb
--- /dev/null
+++ b/core/modules/file/tests/file_deprecated_test/file_deprecated_test.module
@@ -0,0 +1,35 @@
+<?php
+
+/**
+ * @file
+ * Support module for testing deprecated file features.
+ */
+
+declare(strict_types=1);
+
+// cspell:ignore garply tarz
+
+/**
+ * Implements hook_file_mimetype_mapping_alter().
+ *
+ * @deprecated in drupal:11.2.0 and is removed from drupal:12.0.0. Kept only for BC test coverage, see \Drupal\KernelTests\Core\File\MimeTypeLegacyTest.
+ *
+ * @see https://www.drupal.org/node/3494040
+ */
+function file_deprecated_test_file_mimetype_mapping_alter(&$mapping): void {
+  // Add new mappings.
+  $mapping['mimetypes']['file_test_mimetype_1'] = 'made_up/file_test_1';
+  $mapping['mimetypes']['file_test_mimetype_2'] = 'made_up/file_test_2';
+  $mapping['mimetypes']['file_test_mimetype_3'] = 'made_up/doc';
+  $mapping['mimetypes']['application-x-compress'] = 'application/x-compress';
+  $mapping['mimetypes']['application-x-tarz'] = 'application/x-tarz';
+  $mapping['mimetypes']['application-x-garply-waldo'] = 'application/x-garply-waldo';
+  $mapping['extensions']['file_test_1'] = 'file_test_mimetype_1';
+  $mapping['extensions']['file_test_2'] = 'file_test_mimetype_2';
+  $mapping['extensions']['file_test_3'] = 'file_test_mimetype_2';
+  $mapping['extensions']['z'] = 'application-x-compress';
+  $mapping['extensions']['tar.z'] = 'application-x-tarz';
+  $mapping['extensions']['garply.waldo'] = 'application-x-garply-waldo';
+  // Override existing mapping.
+  $mapping['extensions']['doc'] = 'file_test_mimetype_3';
+}
diff --git a/core/modules/file/tests/file_test/file_test.services.yml b/core/modules/file/tests/file_test/file_test.services.yml
index e70db1ebd65..095f9e42c0c 100644
--- a/core/modules/file/tests/file_test/file_test.services.yml
+++ b/core/modules/file/tests/file_test/file_test.services.yml
@@ -20,3 +20,6 @@ services:
     tags:
       - { name: stream_wrapper, scheme: dummy1 }
       - { name: stream_wrapper, scheme: dummy2 }
+  Drupal\file_test\EventSubscriber\DummyMimeTypeMapLoadedSubscriber:
+    autowire: true
+    public: false
diff --git a/core/modules/file/tests/file_test/src/EventSubscriber/DummyMimeTypeMapLoadedSubscriber.php b/core/modules/file/tests/file_test/src/EventSubscriber/DummyMimeTypeMapLoadedSubscriber.php
new file mode 100644
index 00000000000..9f9e5e98438
--- /dev/null
+++ b/core/modules/file/tests/file_test/src/EventSubscriber/DummyMimeTypeMapLoadedSubscriber.php
@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\file_test\EventSubscriber;
+
+use Drupal\Core\File\Event\MimeTypeMapLoadedEvent;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+
+// cspell:ignore garply tarz
+
+/**
+ * Modifies the MIME type map by adding dummy mappings.
+ */
+class DummyMimeTypeMapLoadedSubscriber implements EventSubscriberInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function onMimeTypeMapLoaded(MimeTypeMapLoadedEvent $event): void {
+    // Add new mappings.
+    $event->map->addMapping('made_up/file_test_1', 'file_test_1');
+    $event->map->addMapping('made_up/file_test_2', 'file_test_2');
+    $event->map->addMapping('made_up/file_test_2', 'file_test_3');
+    $event->map->addMapping('application/x-compress', 'z');
+    $event->map->addMapping('application/x-tarz', 'tar.z');
+    $event->map->addMapping('application/x-garply-waldo', 'garply.waldo');
+    // Override existing mapping.
+    $event->map->addMapping('made_up/doc', 'doc');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getSubscribedEvents(): array {
+    return [
+      MimeTypeMapLoadedEvent::class => 'onMimeTypeMapLoaded',
+    ];
+  }
+
+}
diff --git a/core/modules/file/tests/file_test/src/Hook/FileTestHooks.php b/core/modules/file/tests/file_test/src/Hook/FileTestHooks.php
index c58c2eba4fd..f23949b6b95 100644
--- a/core/modules/file/tests/file_test/src/Hook/FileTestHooks.php
+++ b/core/modules/file/tests/file_test/src/Hook/FileTestHooks.php
@@ -4,10 +4,10 @@ declare(strict_types=1);
 
 namespace Drupal\file_test\Hook;
 
+use Drupal\Core\Hook\Attribute\Hook;
 use Drupal\file\Entity\File;
 use Drupal\file_test\FileTestCdn;
 use Drupal\file_test\FileTestHelper;
-use Drupal\Core\Hook\Attribute\Hook;
 
 // cspell:ignore tarz
 // cspell:ignore garply
@@ -167,28 +167,6 @@ class FileTestHooks {
   }
 
   /**
-   * Implements hook_file_mimetype_mapping_alter().
-   */
-  #[Hook('file_mimetype_mapping_alter')]
-  public function fileMimetypeMappingAlter(&$mapping): void {
-    // Add new mappings.
-    $mapping['mimetypes']['file_test_mimetype_1'] = 'made_up/file_test_1';
-    $mapping['mimetypes']['file_test_mimetype_2'] = 'made_up/file_test_2';
-    $mapping['mimetypes']['file_test_mimetype_3'] = 'made_up/doc';
-    $mapping['mimetypes']['application-x-compress'] = 'application/x-compress';
-    $mapping['mimetypes']['application-x-tarz'] = 'application/x-tarz';
-    $mapping['mimetypes']['application-x-garply-waldo'] = 'application/x-garply-waldo';
-    $mapping['extensions']['file_test_1'] = 'file_test_mimetype_1';
-    $mapping['extensions']['file_test_2'] = 'file_test_mimetype_2';
-    $mapping['extensions']['file_test_3'] = 'file_test_mimetype_2';
-    $mapping['extensions']['z'] = 'application-x-compress';
-    $mapping['extensions']['tar.z'] = 'application-x-tarz';
-    $mapping['extensions']['garply.waldo'] = 'application-x-garply-waldo';
-    // Override existing mapping.
-    $mapping['extensions']['doc'] = 'file_test_mimetype_3';
-  }
-
-  /**
    * Implements hook_entity_type_alter().
    */
   #[Hook('entity_type_alter')]
diff --git a/core/modules/responsive_image/responsive_image.module b/core/modules/responsive_image/responsive_image.module
index 90b1fb26b01..9fe3dc72b50 100644
--- a/core/modules/responsive_image/responsive_image.module
+++ b/core/modules/responsive_image/responsive_image.module
@@ -4,6 +4,7 @@
  * @file
  */
 
+use Drupal\Core\File\MimeType\MimeTypeMapInterface;
 use Drupal\Core\Template\Attribute;
 use Drupal\Core\Logger\RfcLogLevel;
 use Drupal\image\Entity\ImageStyle;
@@ -435,22 +436,25 @@ function responsive_image_get_image_dimensions($image_style_name, array $dimensi
  * @param string $extension
  *   The original extension of the image (without the leading dot).
  *
- * @return string
- *   The MIME type of the image after the image style is applied.
+ * @return string|null
+ *   The MIME type of the image after the image style is applied, or NULL if not
+ *   found.
  */
 function responsive_image_get_mime_type($image_style_name, $extension) {
-  if ($image_style_name == ResponsiveImageStyleInterface::EMPTY_IMAGE) {
-    return 'image/gif';
-  }
-  // The MIME type guesser needs a full path, not just an extension, but the
-  // file doesn't have to exist.
-  if ($image_style_name === ResponsiveImageStyleInterface::ORIGINAL_IMAGE) {
-    $fake_path = 'responsive_image.' . $extension;
-  }
-  else {
-    $fake_path = 'responsive_image.' . ImageStyle::load($image_style_name)->getDerivativeExtension($extension);
-  }
-  return \Drupal::service('file.mime_type.guesser.extension')->guessMimeType($fake_path);
+  $extension = match ($image_style_name) {
+    // The file extension for the empty image is 'gif'.
+    ResponsiveImageStyleInterface::EMPTY_IMAGE => 'gif',
+    // If using the original image, the file extension is just passed on to the
+    // MIME type mapper.
+    ResponsiveImageStyleInterface::ORIGINAL_IMAGE => $extension,
+    // In all other cases, get the file extension of the derivative image from
+    // the image style configuration.
+    default => ImageStyle::load($image_style_name)->getDerivativeExtension($extension),
+  };
+
+  return \Drupal::service(MimeTypeMapInterface::class)->getMimeTypeForExtension(
+    $extension
+  );
 }
 
 /**
diff --git a/core/tests/Drupal/KernelTests/Core/File/ExtensionMimeTypeGuesserDeprecationTest.php b/core/tests/Drupal/KernelTests/Core/File/ExtensionMimeTypeGuesserDeprecationTest.php
new file mode 100644
index 00000000000..e00864d2e45
--- /dev/null
+++ b/core/tests/Drupal/KernelTests/Core/File/ExtensionMimeTypeGuesserDeprecationTest.php
@@ -0,0 +1,42 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\KernelTests\Core\File;
+
+use Drupal\Core\File\MimeType\ExtensionMimeTypeGuesser;
+use Drupal\KernelTests\KernelTestBase;
+
+/**
+ * Tests that deprecation messages are raised for deprecations.
+ *
+ * @covers \Drupal\Core\File\MimeType\ExtensionMimeTypeGuesser
+ * @group file
+ * @group legacy
+ *
+ * @todo Remove this class once deprecations are removed.
+ */
+class ExtensionMimeTypeGuesserDeprecationTest extends KernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['system', 'file_deprecated_test'];
+
+  /**
+   * Tests that deprecations are raised for missing constructor arguments.
+   *
+   * @covers \Drupal\Core\File\MimeType\ExtensionMimeTypeGuesser::__construct
+   * @group legacy
+   */
+  public function testConstructorDeprecation(): void {
+    $this->expectDeprecation(
+      'Calling Drupal\Core\File\MimeType\ExtensionMimeTypeGuesser::__construct() with the $map argument as an instance of \Drupal\Core\Extension\ModuleHandlerInterface is deprecated in drupal:11.2.0 and an instance of \Drupal\Core\File\MimeType\MimeTypeMapInterface is required in drupal:12.0.0. See https://www.drupal.org/node/3494040'
+    );
+
+    new ExtensionMimeTypeGuesser(
+      \Drupal::service('module_handler'),
+    );
+  }
+
+}
diff --git a/core/tests/Drupal/KernelTests/Core/File/MimeType/ExtensionMimeTypeGuesserTest.php b/core/tests/Drupal/KernelTests/Core/File/MimeType/ExtensionMimeTypeGuesserTest.php
new file mode 100644
index 00000000000..9dbd3ef8e9a
--- /dev/null
+++ b/core/tests/Drupal/KernelTests/Core/File/MimeType/ExtensionMimeTypeGuesserTest.php
@@ -0,0 +1,133 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\KernelTests\Core\File\MimeType;
+
+use Drupal\KernelTests\KernelTestBase;
+
+// cspell:ignore garply tarz
+
+/**
+ * Tests filename mimetype detection.
+ *
+ * @group File
+ * @coversDefaultClass \Drupal\Core\File\MimeType\ExtensionMimeTypeGuesser
+ */
+class ExtensionMimeTypeGuesserTest extends KernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['file_deprecated_test', 'file_test'];
+
+  /**
+   * Tests mapping of mimetypes from filenames.
+   *
+   * @covers ::guessMimeType
+   * @group legacy
+   */
+  public function testGuessMimeType(): void {
+    $prefixes = ['public://', 'private://', 'temporary://', 'dummy-remote://'];
+
+    $test_case = [
+      'test.jar' => 'application/java-archive',
+      'test.jpeg' => 'image/jpeg',
+      'test.JPEG' => 'image/jpeg',
+      'test.jpg' => 'image/jpeg',
+      'test.jar.jpg' => 'image/jpeg',
+      'test.jpg.jar' => 'application/java-archive',
+      'test.pcf.Z' => 'application/x-font',
+      'test.garply.waldo' => 'application/x-garply-waldo',
+      'pcf.z' => 'application/x-compress',
+      'jar' => NULL,
+      'garply.waldo' => NULL,
+      'some.junk' => NULL,
+      // Mime type added by file_test_mimetype_alter()
+      'foo.file_test_1' => 'made_up/file_test_1',
+      'foo.file_test_2' => 'made_up/file_test_2',
+      'foo.doc' => 'made_up/doc',
+      'test.ogg' => 'audio/ogg',
+      'foobar.z' => 'application/x-compress',
+      'foobar.tar' => 'application/x-tar',
+      'foobar.tar.z' => 'application/x-tarz',
+      'foobar.0.zip' => 'application/zip',
+      'foobar..zip' => 'application/zip',
+    ];
+
+    $this->expectDeprecation(
+      'The deprecated alter hook hook_file_mimetype_mapping_alter() is implemented in these locations: file_deprecated_test_file_mimetype_mapping_alter. This hook is deprecated in drupal:11.2.0 and is removed from drupal:12.0.0. Implement a \Drupal\Core\File\Event\MimeTypeMapLoadedEvent listener instead. See https://www.drupal.org/node/3494040'
+    );
+
+    /** @var \Drupal\Core\File\MimeType\ExtensionMimeTypeGuesser $guesser */
+    $guesser = \Drupal::service('file.mime_type.guesser.extension');
+    // Test using default mappings.
+    foreach ($test_case as $input => $expected) {
+      // Test stream [URI].
+      foreach ($prefixes as $prefix) {
+        $output = $guesser->guessMimeType($prefix . $input);
+        $this->assertSame($expected, $output);
+      }
+
+      // Test normal path equivalent.
+      $output = $guesser->guessMimeType($input);
+      $this->assertSame($expected, $output);
+    }
+  }
+
+  /**
+   * Tests mapping of mimetypes from filenames.
+   *
+   * @group legacy
+   * @covers ::guessMimeType
+   * @covers ::setMapping
+   */
+  public function testFileMimeTypeDetectionCustomMapping(): void {
+    /** @var \Drupal\Core\File\MimeType\ExtensionMimeTypeGuesser $extension_guesser */
+    $extension_guesser = \Drupal::service('file.mime_type.guesser.extension');
+
+    // Pass in a custom mapping.
+    $mapping = [
+      'mimetypes' => [
+        0 => 'application/java-archive',
+        1 => 'image/jpeg',
+      ],
+      'extensions' => [
+        'jar' => 0,
+        'jpg' => 1,
+      ],
+    ];
+
+    $this->expectDeprecation(
+      'Drupal\Core\File\MimeType\ExtensionMimeTypeGuesser::setMapping() is deprecated in drupal:11.2.0 and is removed from drupal:12.0.0. Use \Drupal\Core\File\MimeType\MimeTypeMapInterface::addMapping() instead or define your own MimeTypeMapInterface implementation. See https://www.drupal.org/node/3494040'
+    );
+    $extension_guesser->setMapping($mapping);
+
+    $test_case = [
+      'test.jar' => 'application/java-archive',
+      'test.jpeg' => 'image/jpeg',
+      'test.jpg' => 'image/jpeg',
+      'test.jar.jpg' => 'image/jpeg',
+      'test.jpg.jar' => 'application/java-archive',
+      'test.pcf.z' => 'application/x-font',
+      'test.garply.waldo' => 'application/x-garply-waldo',
+      'pcf.z' => 'application/x-compress',
+      'jar' => NULL,
+      'garply.waldo' => NULL,
+      'some.junk' => NULL,
+      'foo.file_test_1' => 'made_up/file_test_1',
+      'foo.file_test_2' => 'made_up/file_test_2',
+      'foo.doc' => 'made_up/doc',
+      'test.ogg' => 'audio/ogg',
+      'foobar.z' => 'application/x-compress',
+      'foobar.tar' => 'application/x-tar',
+      'foobar.tar.z' => 'application/x-tarz',
+    ];
+
+    foreach ($test_case as $input => $expected) {
+      $output = $extension_guesser->guessMimeType($input);
+      $this->assertSame($expected, $output, 'Failed for extension ' . $input);
+    }
+  }
+
+}
diff --git a/core/tests/Drupal/KernelTests/Core/File/MimeType/LegacyMimeTypeTest.php b/core/tests/Drupal/KernelTests/Core/File/MimeType/LegacyMimeTypeTest.php
new file mode 100644
index 00000000000..ae713fc27ae
--- /dev/null
+++ b/core/tests/Drupal/KernelTests/Core/File/MimeType/LegacyMimeTypeTest.php
@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\KernelTests\Core\File\MimeType;
+
+use Drupal\Core\File\MimeType\MimeTypeMapInterface;
+use Drupal\KernelTests\KernelTestBase;
+
+/**
+ * Tests deprecated file features.
+ *
+ * @group legacy
+ * @group File
+ */
+class LegacyMimeTypeTest extends KernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['system', 'file_deprecated_test'];
+
+  /**
+   * Tests deprecation of hook_file_mimetype_mapping_alter.
+   *
+   * @group legacy
+   */
+  public function testHookFileMimetypeMappingAlter(): void {
+    $this->expectDeprecation(
+      'The deprecated alter hook hook_file_mimetype_mapping_alter() is implemented in these locations: file_deprecated_test_file_mimetype_mapping_alter. This hook is deprecated in drupal:11.2.0 and is removed from drupal:12.0.0. Implement a \Drupal\Core\File\Event\MimeTypeMapLoadedEvent listener instead. See https://www.drupal.org/node/3494040'
+    );
+
+    $map = \Drupal::service(MimeTypeMapInterface::class);
+    $this->assertEquals(['file_test_2', 'file_test_3'],
+      $map->getExtensionsForMimeType('made_up/file_test_2'));
+  }
+
+}
diff --git a/core/tests/Drupal/KernelTests/Core/File/MimeTypeTest.php b/core/tests/Drupal/KernelTests/Core/File/MimeTypeTest.php
deleted file mode 100644
index 653902e9f58..00000000000
--- a/core/tests/Drupal/KernelTests/Core/File/MimeTypeTest.php
+++ /dev/null
@@ -1,106 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Drupal\KernelTests\Core\File;
-
-// cspell:ignore garply tarz
-
-/**
- * Tests filename mimetype detection.
- *
- * @group File
- */
-class MimeTypeTest extends FileTestBase {
-
-  /**
-   * {@inheritdoc}
-   */
-  protected static $modules = ['file_test'];
-
-  /**
-   * Tests mapping of mimetypes from filenames.
-   */
-  public function testFileMimeTypeDetection(): void {
-    $prefixes = ['public://', 'private://', 'temporary://', 'dummy-remote://'];
-
-    $test_case = [
-      'test.jar' => 'application/java-archive',
-      'test.jpeg' => 'image/jpeg',
-      'test.JPEG' => 'image/jpeg',
-      'test.jpg' => 'image/jpeg',
-      'test.jar.jpg' => 'image/jpeg',
-      'test.jpg.jar' => 'application/java-archive',
-      'test.pcf.Z' => 'application/x-font',
-      'test.garply.waldo' => 'application/x-garply-waldo',
-      'pcf.z' => 'application/x-compress',
-      'jar' => 'application/octet-stream',
-      'garply.waldo' => 'application/octet-stream',
-      'some.junk' => 'application/octet-stream',
-      'foo.file_test_1' => 'made_up/file_test_1',
-      'foo.file_test_2' => 'made_up/file_test_2',
-      'foo.doc' => 'made_up/doc',
-      'test.ogg' => 'audio/ogg',
-      'foobar.z' => 'application/x-compress',
-      'foobar.tar' => 'application/x-tar',
-      'foobar.tar.z' => 'application/x-tarz',
-      'foobar.0.zip' => 'application/zip',
-      'foobar..zip' => 'application/zip',
-    ];
-
-    $guesser = $this->container->get('file.mime_type.guesser');
-    // Test using default mappings.
-    foreach ($test_case as $input => $expected) {
-      // Test stream [URI].
-      foreach ($prefixes as $prefix) {
-        $output = $guesser->guessMimeType($prefix . $input);
-        $this->assertSame($expected, $output);
-      }
-
-      // Test normal path equivalent
-      $output = $guesser->guessMimeType($input);
-      $this->assertSame($expected, $output);
-    }
-
-    // Now test the extension guesser by passing in a custom mapping.
-    $mapping = [
-      'mimetypes' => [
-        0 => 'application/java-archive',
-        1 => 'image/jpeg',
-      ],
-      'extensions' => [
-        'jar' => 0,
-        'jpg' => 1,
-      ],
-    ];
-
-    $test_case = [
-      'test.jar' => 'application/java-archive',
-      'test.jpeg' => NULL,
-      'test.jpg' => 'image/jpeg',
-      'test.jar.jpg' => 'image/jpeg',
-      'test.jpg.jar' => 'application/java-archive',
-      'test.pcf.z' => NULL,
-      'test.garply.waldo' => NULL,
-      'pcf.z' => NULL,
-      'jar' => NULL,
-      'garply.waldo' => NULL,
-      'some.junk' => NULL,
-      'foo.file_test_1' => NULL,
-      'foo.file_test_2' => NULL,
-      'foo.doc' => NULL,
-      'test.ogg' => NULL,
-      'foobar.z' => NULL,
-      'foobar.tar' => NULL,
-      'foobar.tar.z' => NULL,
-    ];
-    $extension_guesser = $this->container->get('file.mime_type.guesser.extension');
-    $extension_guesser->setMapping($mapping);
-
-    foreach ($test_case as $input => $expected) {
-      $output = $extension_guesser->guessMimeType($input);
-      $this->assertSame($expected, $output);
-    }
-  }
-
-}
diff --git a/core/tests/Drupal/Tests/Core/File/MimeType/MimeTypeMapTest.php b/core/tests/Drupal/Tests/Core/File/MimeType/MimeTypeMapTest.php
new file mode 100644
index 00000000000..c0a7995b15c
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/File/MimeType/MimeTypeMapTest.php
@@ -0,0 +1,116 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\Core\File\MimeType;
+
+use Drupal\Core\File\MimeType\MimeTypeMap;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * Tests the MIME type mapper to extension.
+ *
+ * @coversDefaultClass \Drupal\Core\File\MimeType\MimeTypeMap
+ *
+ * @group File
+ */
+class MimeTypeMapTest extends UnitTestCase {
+
+  /**
+   * The default MIME type map under test.
+   */
+  protected MimeTypeMap $map;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+    $this->map = new MimeTypeMap();
+  }
+
+  /**
+   * @covers ::addMapping
+   */
+  public function testAddMapping(): void {
+    $this->map->addMapping('image/gif', 'gif');
+    $this->assertEquals(
+      'image/gif',
+      $this->map->getMimeTypeForExtension('gif')
+    );
+
+    $this->map->addMapping('image/jpeg', 'jpeg');
+    $this->assertEquals(
+      'image/jpeg',
+      $this->map->getMimeTypeForExtension('jpeg')
+    );
+  }
+
+  /**
+   * @covers ::removeMapping
+   */
+  public function testRemoveMapping(): void {
+    $this->assertTrue($this->map->removeMapping('image/jpeg', 'jpg'));
+    $this->assertNull($this->map->getMimeTypeForExtension('jpg'));
+    $this->assertFalse($this->map->removeMapping('bar', 'foo'));
+  }
+
+  /**
+   * @covers ::removeMimeType
+   */
+  public function testRemoveMimeType(): void {
+    $this->assertTrue($this->map->removeMimeType('image/jpeg'));
+    $this->assertNull($this->map->getMimeTypeForExtension('jpg'));
+    $this->assertFalse($this->map->removeMimeType('foo/bar'));
+  }
+
+  /**
+   * @covers ::listMimeTypes
+   */
+  public function testListMimeTypes(): void {
+    $mimeTypes = $this->map->listMimeTypes();
+    $this->assertContains('application/java-archive', $mimeTypes);
+    $this->assertContains('image/jpeg', $mimeTypes);
+  }
+
+  /**
+   * @covers ::hasMimeType
+   */
+  public function testHasMimeType(): void {
+    $this->assertTrue($this->map->hasMimeType('image/jpeg'));
+    $this->assertFalse($this->map->hasMimeType('foo/bar'));
+  }
+
+  /**
+   * @covers ::getMimeTypeForExtension
+   */
+  public function testGetMimeTypeForExtension(): void {
+    $this->assertSame('image/jpeg', $this->map->getMimeTypeForExtension('jpe'));
+  }
+
+  /**
+   * @covers ::getExtensionsForMimeType
+   */
+  public function testGetExtensionsForMimeType(): void {
+    $this->assertEquals(['jpe', 'jpeg', 'jpg'],
+      $this->map->getExtensionsForMimeType('image/jpeg'));
+  }
+
+  /**
+   * @covers ::listExtensions
+   */
+  public function testListExtension(): void {
+    $extensions = $this->map->listExtensions();
+    $this->assertContains('jar', $extensions);
+    $this->assertContains('jpg', $extensions);
+  }
+
+  /**
+   * @covers ::hasExtension
+   */
+  public function testHasExtension(): void {
+    $this->assertTrue($this->map->hasExtension('jpg'));
+    $this->assertFalse($this->map->hasExtension('foo'));
+  }
+
+}