Issue #2905429 by zrpnr, tim.plunkett, Wim Leers, Jacine: Library definitions...

Issue #2905429 by zrpnr, tim.plunkett, Wim Leers, Jacine: Library definitions containing only dependencies should be valid

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

@@ -102,7 +102,7 @@ public function buildByExtension($extension) {
     $libraries = $this->applyLibrariesOverride($libraries, $extension);
 
     foreach ($libraries as $id => &$library) {
-      if (!isset($library['js']) && !isset($library['css']) && !isset($library['drupalSettings'])) {
+      if (!isset($library['js']) && !isset($library['css']) && !isset($library['drupalSettings']) && !isset($library['dependencies'])) {
         throw new IncompleteLibraryDefinitionException(sprintf("Incomplete library definition for definition '%s' in extension '%s'", $id, $extension));
       }
       $library += ['dependencies' => [], 'js' => [], 'css' => []];

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

@@ -172,7 +172,26 @@ public function testInvalidLibrariesFile() {
   }
 
   /**
-   * Tests that an exception is thrown when no CSS/JS/setting is specified.
+   * Tests that no exception is thrown when only dependencies are specified.
+   *
+   * @covers ::buildByExtension
+   */
+  public function testBuildByExtensionWithOnlyDependencies() {
+    $this->moduleHandler->expects($this->atLeastOnce())
+      ->method('moduleExists')
+      ->with('example_module_only_dependencies')
+      ->will($this->returnValue(TRUE));
+
+    $path = __DIR__ . '/library_test_files';
+    $path = substr($path, strlen($this->root) + 1);
+    $this->libraryDiscoveryParser->setPaths('module', 'example_module_only_dependencies', $path);
+
+    $libraries = $this->libraryDiscoveryParser->buildByExtension('example_module_only_dependencies');
+    $this->assertArrayHasKey('example', $libraries);
+  }
+
+  /**
+   * Tests that an exception is thrown with only the version property specified.
    *
    * @covers ::buildByExtension
    */

core/tests/Drupal/Tests/Core/Asset/library_test_files/example_module_only_dependencies.libraries.yml

+example:
+  dependencies: {  }