Add support for tasks to determine whether they are appropriate for a given target

pkg/analyzer/test/src/task/model_test.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.test.src.task.model_test;
 
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/java_engine.dart';
 import 'package:analyzer/src/task/model.dart';
 import 'package:analyzer/task/model.dart';
@@ skipping 85 matching lines @@
   test_create() {
     ResultCachingPolicy policy = new SimpleResultCachingPolicy(256, 32);
     expect(policy.maxActiveSize, 256);
     expect(policy.maxIdleSize, 32);
     expect(policy.measure(null), 1);
   }
 }
 
 @reflectiveTest
 class TaskDescriptorImplTest extends EngineTestCase {
-  test_create() {
+  test_create_noOptionalArgs() {
     String name = 'name';
     BuildTask buildTask = (context, target) {};
     CreateTaskInputs createTaskInputs = (target) {};
     List<ResultDescriptor> results = <ResultDescriptor>[];
     TaskDescriptorImpl descriptor =
         new TaskDescriptorImpl(name, buildTask, createTaskInputs, results);
     expect(descriptor, isNotNull);
     expect(descriptor.name, name);
     expect(descriptor.buildTask, equals(buildTask));
     expect(descriptor.createTaskInputs, equals(createTaskInputs));
+    expect(descriptor.isAppropriateFor(null), isTrue);
+    expect(descriptor.results, results);
+  }
+
+  test_create_withIsAppropriateFor() {
+    String name = 'name';
+    BuildTask buildTask = (context, target) {};
+    CreateTaskInputs createTaskInputs = (target) {};
+    List<ResultDescriptor> results = <ResultDescriptor>[];
+    IsAppropriateFor isAppropriateFor = (target) => false;
+    TaskDescriptorImpl descriptor = new TaskDescriptorImpl(
+        name, buildTask, createTaskInputs, results,
+        isAppropriateFor: isAppropriateFor);
+    expect(descriptor, isNotNull);
+    expect(descriptor.name, name);
+    expect(descriptor.buildTask, equals(buildTask));
+    expect(descriptor.createTaskInputs, equals(createTaskInputs));
+    expect(descriptor.isAppropriateFor(null), isFalse);
     expect(descriptor.results, results);
   }
 
   test_createTask() {
-    BuildTask buildTask = (context, target) =>
-        new TestAnalysisTask(context, target);
+    BuildTask buildTask =
+        (context, target) => new TestAnalysisTask(context, target);
     CreateTaskInputs createTaskInputs = (target) {};
     List<ResultDescriptor> results = <ResultDescriptor>[];
     TaskDescriptorImpl descriptor =
         new TaskDescriptorImpl('name', buildTask, createTaskInputs, results);
     AnalysisContext context = null;
     AnalysisTarget target = new TestSource();
     Map<String, dynamic> inputs = {};
     AnalysisTask createTask = descriptor.createTask(context, target, inputs);
     expect(createTask, isNotNull);
     expect(createTask.context, context);
     expect(createTask.inputs, inputs);
     expect(createTask.target, target);
   }
 }