Initial task support

pkg/analyzer/lib/src/task/general.dart

Index: pkg/analyzer/lib/src/task/general.dart
diff --git a/pkg/analyzer/lib/src/task/general.dart b/pkg/analyzer/lib/src/task/general.dart
new file mode 100644
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+// 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 {
+  /**
+   * 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 = this.source;
+    if (source == null) {
+      return "get contents of <unknown source>";
+    }
+    return "get contents of ${source.fullName}";
+  }
+
+  @override
+  internalPerform() {
+    Source source = target.source;
+    if (source == null) {
+      throw new AnalysisException(
+          "Could not get contents: no source associated with the target");
+    }
+    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);
+  }
+}