Issue #2358981 by tadityar, tstoeckler, larowlan, mpdonadio, Devin Carlson:...

Issue #2358981 by tadityar, tstoeckler, larowlan, mpdonadio, Devin Carlson: Provide a mechanism for dynamic library declarations

core/lib/Drupal/Core/Asset/LibraryDiscovery.php

@@ -79,4 +79,11 @@ public function getLibraryByName($extension, $name) {
     return isset($extension[$name]) ? $extension[$name] : FALSE;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function clearCachedDefinitions() {
+    $this->collector->clear();
+  }
+
 }

core/lib/Drupal/Core/Asset/LibraryDiscoveryInterface.php

@@ -50,4 +50,9 @@ public function getLibrariesByExtension($extension);
    */
   public function getLibraryByName($extension, $name);
 
+  /**
+   * Clears static and persistent library definition caches.
+   */
+  public function clearCachedDefinitions();
+
 }

core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php

@@ -13,6 +13,7 @@
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Component\Serialization\Exception\InvalidDataTypeException;
 use Drupal\Component\Serialization\Yaml;
+use Drupal\Component\Utility\NestedArray;
 
 /**
  * Parses library files to get extension data.
@@ -77,15 +78,11 @@ public function buildByExtension($extension) {
       $path = $this->drupalGetPath($extension_type, $extension);
     }
 
-    $library_file = $path . '/' . $extension . '.libraries.yml';
-
-    if ($library_file && file_exists($this->root . '/' . $library_file)) {
-      $libraries = $this->parseLibraryInfo($extension, $library_file);
-    }
+    $libraries = $this->parseLibraryInfo($extension, $path);
 
     foreach ($libraries as $id => &$library) {
       if (!isset($library['js']) && !isset($library['css']) && !isset($library['drupalSettings'])) {
-        throw new IncompleteLibraryDefinitionException(sprintf("Incomplete library definition for '%s' in %s", $id, $library_file));
+        throw new IncompleteLibraryDefinitionException(sprintf("Incomplete library definition for definition '%s' in extension '%s'", $id, $extension));
       }
       $library += array('dependencies' => array(), 'js' => array(), 'css' => array());
 
@@ -102,7 +99,7 @@ public function buildByExtension($extension) {
 
       // If this is a 3rd party library, the license info is required.
       if (isset($library['remote']) && !isset($library['license'])) {
-        throw new LibraryDefinitionMissingLicenseException(sprintf("Missing license information in library definition for '%s' in %s: it has a remote, but no license.", $id, $library_file));
+        throw new LibraryDefinitionMissingLicenseException(sprintf("Missing license information in library definition for definition '%s' extension '%s': it has a remote, but no license.", $id, $extension));
       }
 
       // Assign Drupal's license to libraries that don't have license info.
@@ -209,8 +206,8 @@ public function buildByExtension($extension) {
    *
    * @param string $extension
    *   The name of the extension that registered a library.
-   * @param string $library_file
-   *   The relative filename to the DRUPAL_ROOT of the wanted library file.
+   * @param string $path
+   *   The relative path to the extension.
    *
    * @return array
    *   An array of parsed library data.
@@ -218,14 +215,26 @@ public function buildByExtension($extension) {
    * @throws \Drupal\Core\Asset\Exception\InvalidLibraryFileException
    *   Thrown when a parser exception got thrown.
    */
-  protected function parseLibraryInfo($extension, $library_file) {
-    try {
-      $libraries = Yaml::decode(file_get_contents($this->root . '/' . $library_file));
+  protected function parseLibraryInfo($extension, $path) {
+    $libraries = [];
+
+    $library_file = $path . '/' . $extension . '.libraries.yml';
+    if (file_exists($this->root . '/' . $library_file)) {
+      try {
+        $libraries = Yaml::decode(file_get_contents($this->root . '/' . $library_file));
+      }
+      catch (InvalidDataTypeException $e) {
+        // Rethrow a more helpful exception to provide context.
+        throw new InvalidLibraryFileException(sprintf('Invalid library definition in %s: %s', $library_file, $e->getMessage()), 0, $e);
+      }
     }
-    catch (InvalidDataTypeException $e) {
-      // Rethrow a more helpful exception to provide context.
-      throw new InvalidLibraryFileException(sprintf('Invalid library definition in %s: %s', $library_file, $e->getMessage()), 0, $e);
+
+    // Allow modules to add dynamic library definitions.
+    $hook = 'library_info_build';
+    if ($this->moduleHandler->implementsHook($extension, $hook)) {
+      $libraries = NestedArray::mergeDeep($libraries, $this->moduleHandler->invoke($extension, $hook));
     }
+
     // Allow modules to alter the module's registered libraries.
     $this->moduleHandler->alter('library_info', $libraries, $extension);
 

core/modules/system/src/Tests/Common/AttachedAssetsTest.php

@@ -374,6 +374,28 @@ function testLibraryAlter() {
     $this->assertTrue(strpos($scripts, 'core/assets/vendor/jquery-form/jquery.form.js'), 'Altered library dependencies are added to the page.');
   }
 
+  /**
+   * Dynamically defines an asset library and alters it.
+   */
+  function testDynamicLibrary() {
+    /** @var \Drupal\Core\Asset\LibraryDiscoveryInterface $library_discovery */
+    $library_discovery = \Drupal::service('library.discovery');
+    // Retrieve a dynamic library definition.
+    // @see common_test_library_info_build()
+    \Drupal::state()->set('common_test.library_info_build_test', TRUE);
+    $library_discovery->clearCachedDefinitions();
+    $dynamic_library = $library_discovery->getLibraryByName('common_test', 'dynamic_library');
+    $this->assertTrue(is_array($dynamic_library));
+    if ($this->assertTrue(isset($dynamic_library['version']))) {
+      $this->assertIdentical('1.0', $dynamic_library['version']);
+    }
+    // Make sure the dynamic library definition could be altered.
+    // @see common_test_library_info_alter()
+    if ($this->assertTrue(isset($dynamic_library['dependencies']))) {
+      $this->assertIdentical(['core/jquery'], $dynamic_library['dependencies']);
+    }
+  }
+
   /**
    * Tests that multiple modules can implement libraries with the same name.
    *

core/modules/system/tests/modules/common_test/common_test.module

@@ -164,6 +164,22 @@ function common_test_preprocess_common_test_render_element(&$variables) {
   $variables['#attached']['library'][] = 'test/specific_preprocess';
 }
 
+/**
+ * Implements hook_library_info_build().
+ */
+function common_test_library_info_build() {
+  $libraries = [];
+  if (\Drupal::state()->get('common_test.library_info_build_test')) {
+    $libraries['dynamic_library'] = [
+      'version' => '1.0',
+      'css' => [
+        'common_test.css' => [],
+      ],
+    ];
+  }
+  return $libraries;
+}
+
 /**
  * Implements hook_library_info_alter().
  */
@@ -174,6 +190,13 @@ function common_test_library_info_alter(&$libraries, $module) {
     // Make Farbtastic depend on jQuery Form to test library dependencies.
     $libraries['jquery.farbtastic']['dependencies'][] = 'core/jquery.form';
   }
+
+  // Alter the dynamically registered library definition.
+  if ($module == 'common_test' && isset($libraries['dynamic_library'])) {
+    $libraries['dynamic_library']['dependencies'] = [
+      'core/jquery',
+    ];
+  }
 }
 
 /**

core/modules/system/theme.api.php

@@ -721,6 +721,70 @@ function hook_js_alter(&$javascript) {
   $javascript['core/assets/vendor/jquery/jquery.min.js']['data'] = drupal_get_path('module', 'jquery_update') . '/jquery.js';
 }
 
+/**
+ * Add dynamic library definitions.
+ *
+ * Modules may implement this hook to add dynamic library definitions. Static
+ * libraries, which do not depend on any runtime information, should be declared
+ * in a modulename.libraries.yml file instead.
+ *
+ * @return array[]
+ *   An array of library definitions to register, keyed by library ID. The
+ *   library ID will be prefixed with the module name automatically.
+ *
+ * @see core.libraries.yml
+ * @see hook_library_info_alter()
+ */
+function hook_library_info_build() {
+  $libraries = [];
+  // Add a library whose information changes depending on certain conditions.
+  $libraries['mymodule.zombie'] = [
+    'dependencies' => [
+      'core/backbone',
+    ],
+  ];
+  if (Drupal::moduleHandler()->moduleExists('minifyzombies')) {
+    $libraries['mymodule.zombie'] += [
+      'js' => [
+        'mymodule.zombie.min.js' => [],
+      ],
+      'css' => [
+        'mymodule.zombie.min.css' => [],
+      ],
+    ];
+  }
+  else {
+    $libraries['mymodule.zombie'] += [
+      'js' => [
+        'mymodule.zombie.js' => [],
+      ],
+      'css' => [
+        'mymodule.zombie.css' => [],
+      ],
+    ];
+  }
+
+  // Add a library only if a certain condition is met. If code wants to
+  // integrate with this library it is safe to (try to) load it unconditionally
+  // without reproducing this check. If the library definition does not exist
+  // the library (of course) not be loaded but no notices or errors will be
+  // triggered.
+  if (Drupal::moduleHandler()->moduleExists('vampirize')) {
+    $libraries['mymodule.vampire'] = [
+      'js' => [
+        'js/vampire.js' => [],
+      ],
+      'css' => [
+        'css/vampire.css',
+      ],
+      'dependencies' => [
+        'core/jquery',
+      ],
+    ];
+  }
+  return $libraries;
+}
+
 /**
  * Perform necessary alterations to the JavaScript settings (drupalSettings).
  *

core/tests/Drupal/Tests/Core/Asset/LibraryDiscoveryParserTest.php

@@ -161,7 +161,7 @@ public function testInvalidLibrariesFile() {
    * Tests that an exception is thrown when no CSS/JS/setting is specified.
    *
    * @expectedException \Drupal\Core\Asset\Exception\IncompleteLibraryDefinitionException
-   * @expectedExceptionMessage Incomplete library definition for 'example' in core/tests/Drupal/Tests/Core/Asset/library_test_files/example_module_missing_information.libraries.yml
+   * @expectedExceptionMessage Incomplete library definition for definition 'example' in extension 'example_module_missing_information'
    *
    * @covers ::buildByExtension
    */
@@ -400,7 +400,7 @@ public function testLibraryWithJavaScript() {
    * Tests that an exception is thrown when license is missing when 3rd party.
    *
    * @expectedException \Drupal\Core\Asset\Exception\LibraryDefinitionMissingLicenseException
-   * @expectedExceptionMessage Missing license information in library definition for 'no-license-info-but-remote' in core/tests/Drupal/Tests/Core/Asset/library_test_files/licenses_missing_information.libraries.yml: it has a remote, but no license.
+   * @expectedExceptionMessage Missing license information in library definition for definition 'no-license-info-but-remote' extension 'licenses_missing_information': it has a remote, but no license.
    *
    * @covers ::buildByExtension
    */
@@ -434,7 +434,6 @@ public function testLibraryWithLicenses() {
 
     $libraries = $this->libraryDiscoveryParser->buildByExtension('licenses');
 
-
     // For libraries without license info, the default license is applied.
     $library = $libraries['no-license-info'];
     $this->assertCount(1, $library['css']);