Clean-up the registration of plugins

pkg/analyzer/lib/src/generated/engine.dart

Index: pkg/analyzer/lib/src/generated/engine.dart
diff --git a/pkg/analyzer/lib/src/generated/engine.dart b/pkg/analyzer/lib/src/generated/engine.dart
index 9be1f2d74a84f381e3e4dd6fe0982854fd0ea449..2769209ec272d8a3041481fe41212ef650354126 100644
--- a/pkg/analyzer/lib/src/generated/engine.dart
+++ b/pkg/analyzer/lib/src/generated/engine.dart
@@ -5925,11 +5925,6 @@ class AnalysisEngine {
       InstrumentationService.NULL_SERVICE;
 
   /**
-   * The list of supported plugins for processing by clients.
-   */
-  List<Plugin> _supportedPlugins;
-
-  /**
    * The partition manager being used to manage the shared partitions.
    */
   final PartitionManager partitionManager = new PartitionManager();
@@ -5953,11 +5948,6 @@ class AnalysisEngine {
   bool limitInvalidationInTaskModel = false;
 
   /**
-   * The plugins that are defined outside the `analyzer` package.
-   */
-  List<Plugin> _userDefinedPlugins = <Plugin>[];
-
-  /**
    * The task manager used to manage the tasks used to analyze code.
    */
   TaskManager _taskManager;
@@ -5997,26 +5987,21 @@ class AnalysisEngine {
   }
 
   /**
-   * Return the list of supported plugins for processing by clients.
+   * Return the list of plugins that clients are required to process, either by
+   * creating an [ExtensionManager] or by using the method
+   * [processRequiredPlugins].
    */
-  List<Plugin> get supportedPlugins {
-    if (_supportedPlugins == null) {
-      _supportedPlugins = <Plugin>[
-        enginePlugin,
-        commandLinePlugin,
-        optionsPlugin
-      ];
-      _supportedPlugins.addAll(_userDefinedPlugins);
-    }
-    return _supportedPlugins;
-  }
+  List<Plugin> get requiredPlugins => <Plugin>[enginePlugin];
 
   /**
    * Return the task manager used to manage the tasks used to analyze code.
    */
   TaskManager get taskManager {
     if (_taskManager == null) {
-      new ExtensionManager().processPlugins(supportedPlugins);
+      if (enginePlugin.taskExtensionPoint == null) {
+        throw new IllegalStateException(
+            'The analysis engine plugin has not been registered');
+      }
       _taskManager = new TaskManager();
       _taskManager.addTaskDescriptors(enginePlugin.taskDescriptors);
       // TODO(brianwilkerson) Create a way to associate different results with
@@ -6027,18 +6012,6 @@ class AnalysisEngine {
   }
 
   /**
-   * Set plugins that are defined outside the `analyzer` package.
-   */
-  void set userDefinedPlugins(List<Plugin> plugins) {
-    if (plugins == null) {
-      plugins = <Plugin>[];
-    }
-    _userDefinedPlugins = plugins;
-    _supportedPlugins = null;
-    _taskManager = null;
-  }
-
-  /**
    * Clear any caches holding on to analysis results so that a full re-analysis
    * will be performed the next time an analysis context is created.
    */
@@ -6057,6 +6030,16 @@ class AnalysisEngine {
   }
 
   /**
+   * A utility method that clients can use to process all of the required
+   * plugins. This method can only be used by clients that do not need to
+   * process any other plugins.
+   */
+  void processRequiredPlugins() {
+    ExtensionManager manager = new ExtensionManager();
+    manager.processPlugins(AnalysisEngine.instance.requiredPlugins);
+  }
+
+  /**
    * Return `true` if the given [fileName] is an analysis options file.
    */
   static bool isAnalysisOptionsFileName(String fileName,