Improvements to task model

pkg/analyzer/lib/src/task/general.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 analyzer.src.task.general;
 
 import 'package:analyzer/src/generated/engine.dart' hide AnalysisTask;
-import 'package:analyzer/src/generated/java_engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/task/general.dart';
 import 'package:analyzer/task/model.dart';
 
 /**
- * The description of the task used to get the content of a source.
- */
-final TaskDescriptor GET_CONTENT = new TaskDescriptor(
-    'GET_CONTENT',
-    GetContentTask.createTask,
-    GetContentTask.buildInputs,
-    <ResultDescriptor>[CONTENT, MODIFICATION_TIME]);
-
-/**
  * A task that gets the contents of the source associated with an analysis
  * target.
  */
 class GetContentTask extends AnalysisTask {
   /**
+   * The task descriptor describing this kind of task.
+   */
+  static final TaskDescriptor DESCRIPTOR = new TaskDescriptor(
+      'GET_CONTENT',
+      GetContentTask.createTask,

[scheglov, 2015/01/26 16:10:33]

FYI, we don't need GetContentTask qualifier now.
Just in case if it wasn't an intentional decision.

[Brian Wilkerson, 2015/01/26 16:14:12]

It wasn't. Thanks! I've removed them.

+      GetContentTask.buildInputs,
+      <ResultDescriptor>[CONTENT, MODIFICATION_TIME]);
+
+  /**
    * Initialize a newly created task to access the content of the source
    * associated with the given [target] in the given [context].
    */
   GetContentTask(InternalAnalysisContext context, AnalysisTarget target)
       : super(context, target);
 
   @override
   String get description {
     Source source = target.source;
     if (source == null) {
       return "get contents of <unknown source>";
     }
     return "get contents of ${source.fullName}";
   }
 
   @override
+  TaskDescriptor get descriptor => DESCRIPTOR;
+
+  @override
   internalPerform() {
-    Source source = target.source;
-    if (source == null) {
-      throw new AnalysisException(
-          "Could not get contents: no source associated with the target");
-    }
+    Source source = getRequiredSource();
+
     TimestampedData<String> data = context.getContents(source);
     outputs[CONTENT] = data.data;
     outputs[MODIFICATION_TIME] = data.modificationTime;
   }
 
   /**
    * Return a map from the names of the inputs of this kind of task to the task
    * input descriptors describing those inputs for a task with the given [target].
    */
   static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
     return <String, TaskInput>{};
   }
 
   /**
    * Create a [GetContentTask] based on the given [target] in the given
    * [context].
    */
   static GetContentTask createTask(AnalysisContext context,
       AnalysisTarget target) {
     return new GetContentTask(context, target);
   }
 }