Add support for .sdkext file to analysis server

pkg/analysis_server/lib/src/sdk_ext.dart

Index: pkg/analysis_server/lib/src/sdk_ext.dart
diff --git a/pkg/analysis_server/lib/src/sdk_ext.dart b/pkg/analysis_server/lib/src/sdk_ext.dart
new file mode 100644
index 0000000000000000000000000000000000000000..f7f5f72c6e8ad7136fe86894ab36681d242fce3e
--- /dev/null
+++ b/pkg/analysis_server/lib/src/sdk_ext.dart
@@ -0,0 +1,96 @@
+// 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 sdk.ext;

[Brian Wilkerson, 2015/07/07 19:59:12]

nit: I think following the library naming convention would make this
"analysis_server.src.sdk_ext".

[Cutch, 2015/07/07 20:33:47]

Done.

+
+import 'dart:async';
+import 'dart:collection';
+import 'dart:convert';
+import 'dart:core' hide Resource;
+
+import 'package:analysis_server/uri/resolver_provider.dart';
+import 'package:analyzer/file_system/file_system.dart';
+import 'package:analyzer/source/package_map_resolver.dart';
+import 'package:analyzer/src/generated/source.dart';
+
+// Given a packageMap (from a PackageMapProvider), check in each package's lib

[Brian Wilkerson, 2015/07/07 19:59:11]

nit: The comments should be valid dartdoc comments.

[Cutch, 2015/07/07 20:33:47]

Done.

+// directory for the existence of a `.sdkext` file. This file must contain a
+// JSON encoded map. Each key in the map is a `dart:` library name. Each value
+// is the filename for the given library. For example:
+// {
+//   "dart:sky": "sdk_ext/dart_sky.dart"
+// }
+//
+// If a key doesn't begin with `dart:` it is ignored.
+class SdkExtUriResolver extends UriResolver {
+  static const String DOT_SDK_EXT_NAME = '.sdkext';
+  static const String DART_COLON_PREFIX = 'dart:';
+
+  final Map<String, String> _urlMappings = <String,String>{};
+
+  SdkExtUriResolver(Map<String, List<Folder>> packageMap) {
+    if (packageMap == null) {
+      return;
+    }
+    packageMap.forEach(_processPackage);
+  }
+
+  @override
+  Source resolveAbsolute(Uri uri) {
+    String mapping = _urlMappings[uri.toString()];
+    if (mapping == null) return null;
+
+    Uri fileUri = new Uri.file(mapping);
+    if (!fileUri.isAbsolute) return null;
+
+    JavaFile javaFile = new JavaFile.fromUri(fileUri);
+    return new FileBasedSource(javaFile);

[Brian Wilkerson, 2015/07/07 19:59:11]

This needs to be "new FileBasedSource(javaFile, uri)" in order to preserve the
original URI.

[Cutch, 2015/07/07 20:33:48]

Done.

+  }
+
+  // Given a package name and a list of folders, add any sdk extensions.
+  void _processPackage(String name, List<Folder> libDirs) {
+    for (var libDir in libDirs) {
+      var sdkExt = _readDotSdkExt(libDir);
+      if (sdkExt != null) {
+        _processSdkExt(sdkExt, libDir);
+      }
+    }
+  }
+
+  // Read the contents of $libDir/$DOT_SDK_EXT_NAME as a string.
+  // Returns null if the file doesn't exist.
+  String _readDotSdkExt(Folder libDir) {
+    var file = libDir.getChild(DOT_SDK_EXT_NAME);
+    try {
+      return file.readAsStringSync();
+    } on FileSystemException catch (e) {
+      // File can't be read.
+      return null;
+    }
+  }
+
+  // Given the JSON for an SDK extension and a folder, setup the uri mapping.
+  void _processSdkExt(String sdkExtJSON, Folder libDir) {
+    var sdkExt;
+    try {
+      sdkExt = JSON.decode(sdkExtJSON);
+    } catch (e) {
+      return;
+    }
+    if ((sdkExt == null) || (sdkExt is! Map)) {
+      return;
+    }
+    sdkExt.forEach((k, v) => _processSdkExtension(k, v, libDir));
+  }
+
+  void _processSdkExtension(String name, String file, Folder libDir) {
+    if (!name.startsWith(DART_COLON_PREFIX)) {
+      // SDK extensions must begin with 'dart:'.
+      return;
+    }
+    var key = name;
+    var value = libDir.canonicalizePath(file);
+    _urlMappings[key] = value;
+  }
+}