Fix for duplicate priority sources.

pkg/analysis_server/test/analysis/set_priority_files_test.dart

 // Copyright (c) 2014, 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 test.analysis.set_priority_files;
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:analysis_server/src/domain_analysis.dart';
+import 'package:analyzer/src/generated/engine.dart'
+    show InternalAnalysisContext;
+import 'package:analyzer/src/generated/source.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 import 'package:unittest/unittest.dart';
 
 import '../analysis_abstract.dart';
 import '../mocks.dart';
 import '../utils.dart';
 
 main() {
   initializeTestEnvironment();
   defineReflectiveTests(SetPriorityFilesTest);
 }
 
 @reflectiveTest
 class SetPriorityFilesTest extends AbstractAnalysisTest {
   @override
   void setUp() {
     super.setUp();
     server.handlers = [new AnalysisDomainHandler(server),];
     createProject();
   }
 
   test_fileDoesNotExist() async {
     String file = '$projectPath/doesNotExist.dart';
     Response response = await _setPriorityFile(file);
     expect(response, isResponseSuccess('0'));
   }
 
   test_fileInAnalysisRoot() async {
     addTestFile('');
+    // wait for analysis to ensure that file is know to the context

[Brian Wilkerson, 2015/10/30 00:08:48]

"file is know" --> "the file is known"

+    await server.onAnalysisComplete;
+    // set priority files
     Response response = await _setPriorityFile(testFile);
     expect(response, isResponseSuccess('0'));
+    // verify
+    InternalAnalysisContext context = server.getContainingContext(testFile);
+    List<Source> prioritySources = context.prioritySources;
+    expect(prioritySources, hasLength(1));
+    expect(prioritySources.first.fullName, testFile);
   }
 
   test_fileInSdk() async {
     addTestFile('');
     await server.onAnalysisComplete;
-    Response response = await _setPriorityFile('/lib/convert/convert.dart');
+    // set priority files
+    String filePath = '/lib/convert/convert.dart';
+    Response response = await _setPriorityFile(filePath);
     expect(response, isResponseSuccess('0'));
+    // verify
+    InternalAnalysisContext sdkContext = server.defaultSdk.context;
+    List<Source> prioritySources = sdkContext.prioritySources;
+    expect(prioritySources, hasLength(1));
+    expect(prioritySources.first.fullName, filePath);
   }
 
   test_fileNotInAnalysisRoot() async {
     String path = '/other/file.dart';
     addFile(path, '');
     Response response = await _setPriorityFile(path);
     expect(response.error, isNotNull);
     expect(response.error.code, RequestErrorCode.UNANALYZED_PRIORITY_FILES);
   }
 
   _setPriorityFile(String file) async {
     Request request =
         new AnalysisSetPriorityFilesParams(<String>[file]).toRequest('0');
     return await serverChannel.sendRequest(request);
   }
 }