Initial plugin API

pkg/analysis_server/lib/src/plugin/plugin_impl.dart

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library analysis_server.src.plugin.plugin_impl;
+
+import 'dart:collection';
+
+import 'package:analysis_server/plugin/plugin.dart';
+
+/**
+ * An object that manages the extension points for a single instance of the
+ * analysis server.
+ */
+class ExtensionManager {
+  /**
+   * A table mapping the id's of extension points to the corresponding
+   * extension points.
+   */
+  Map<String, ExtensionPointImpl> extensionPoints =
+      new HashMap<String, ExtensionPointImpl>();
+
+  /**
+   * Process each of the given [plugins] by allowing them to register extension
+   * points and extensions.
+   *
+   * An [ExtensionError] will be thrown if any of the plugins throws such an
+   * exception while registering with this manager.
+   */
+  void processPlugins(List<Plugin> plugins) {
+    for (Plugin plugin in plugins) {

[danrubel, 2015/01/08 19:46:37]

Do we want to validate that none of the plugins in the list has a conflicting
uniqueIdentifier? Or is that done elsewhere?

[Brian Wilkerson, 2015/01/08 22:00:54]

Good question. I'm tempted to check at the point at which the list of plugins is
being set so that we fail faster when there's a problem. (I'm guessing that we
want any kind of error related to plugins to stop the server.

+      plugin.registerExtensionPoints(
+          (String identifier, [ExtensionValidator validator]) {
+        registerExtensionPoint(plugin, identifier, validator);
+      });
+    }
+    for (Plugin plugin in plugins) {
+      plugin.registerExtensions(registerExtension);
+    }
+  }
+
+  /**
+   * Register an [extension] to the extension point with the given unique
+   * [identifier].
+   */
+  void registerExtension(String identifier, Object extension) {
+    ExtensionPointImpl extensionPoint = extensionPoints[identifier];
+    if (extensionPoint == null) {
+      throw new ExtensionError(
+          'There is no extension point with the id "$identifier"');
+    }
+    extensionPoint.add(extension);
+  }
+
+  /**
+   * Register an extension point being defined by the given [plugin] with the
+   * given simple [identifier] and [validator].
+   */
+  ExtensionPoint registerExtensionPoint(Plugin plugin, String identifier,
+      ExtensionValidator validator) {
+    String uniqueIdentifier = Plugin.buildUniqueIdentifier(plugin, identifier);
+    if (extensionPoints.containsKey(uniqueIdentifier)) {
+      throw new ExtensionError(
+          'There is already an extension point with the id "$identifier"');
+    }
+    ExtensionPointImpl extensionPoint =
+        new ExtensionPointImpl(plugin, identifier, validator);
+    extensionPoints[uniqueIdentifier] = extensionPoint;
+    return extensionPoint;
+  }
+}
+
+/**
+ * A concrete representation of an extension point.
+ */
+class ExtensionPointImpl implements ExtensionPoint {
+  @override
+  final Plugin plugin;
+
+  @override
+  final String simpleIdentifier;
+
+  /**
+   * The validator used to validate extensions to this extension point.
+   */
+  final ExtensionValidator validator;
+
+  /**
+   * The list of extensions to this extension point.
+   */
+  final List<Object> _extensions = <Object>[];
+
+  /**
+   * Initialize a newly create extension point to belong to the given [plugin]
+   * and have the given [simpleIdentifier]. If the [validator] is non-`null` it
+   * will be used to validate extensions associated with this extension point.
+   */
+  ExtensionPointImpl(this.plugin, this.simpleIdentifier, this.validator);
+
+  /**
+   * Return a list containing all of the extensions that have been registered
+   * for this extension point.
+   */
+  List<Object> get extensions => new UnmodifiableListView(_extensions);
+
+  /**
+   * Return the identifier used to uniquely identify this extension point. The
+   * unique identifier is the identifier for the plugin, followed by a period
+   * (`.`), followed by the [simpleIdentifier] for the extension point.
+   */
+  String get uniqueIdentifier =>
+      Plugin.buildUniqueIdentifier(plugin, simpleIdentifier);
+
+  /**
+   * Validate that the given [extension] is appropriate for this extension
+   * point, and if it is then add it to the list of registered exceptions.
+   */
+  void add(Object extension) {
+    if (validator != null) {
+      validator(extension);
+    }
+    _extensions.add(extension);
+  }
+}