Fix the resolution of uri-based part-of directives in the SDK (issue 29598)

pkg/analyzer/test/src/dart/sdk/sdk_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 analyzer.test.generated.sdk_test;
 
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/src/context/builder.dart' show EmbedderYamlLocator;
 import 'package:analyzer/src/dart/sdk/sdk.dart';
@@ skipping 232 matching lines @@
     expect(executable.exists, isTrue);
   }
 
   void test_getSdkVersion() {
     FolderBasedDartSdk sdk = _createDartSdk();
     String version = sdk.sdkVersion;
     expect(version, isNotNull);
     expect(version.length > 0, isTrue);
   }
 
+  /**
+   * The "part" format should result in the same source as the non-part format
+   * when the file is the library file.
+   */
+  void test_mapDartUri_partFormatForLibrary() {
+    FolderBasedDartSdk sdk = _createDartSdk();
+    Source normalSource = sdk.mapDartUri('dart:core');
+    Source partSource = sdk.mapDartUri('dart:core/core.dart');
+    expect(partSource, normalSource);
+  }
+
   void test_useSummary_afterContextCreation() {
     FolderBasedDartSdk sdk = _createDartSdk();
     sdk.context;
     expect(() {
       sdk.useSummary = true;
     }, throwsStateError);
   }
 
   void test_useSummary_beforeContextCreation() {
     FolderBasedDartSdk sdk = _createDartSdk();
@@ skipping 196 matching lines @@
     expect(second, isNotNull);
     expect(second.category, "Server");
     expect(second.path, "second/second.dart");
     expect(second.shortName, "dart:second");
     expect(second.isDart2JsLibrary, false);
     expect(second.isDocumented, false);
     expect(second.isImplementation, true);
     expect(second.isVmLibrary, false);
   }
 }