Removed fixed dependencies

packages/analyzer/lib/src/dart/sdk/sdk.dart

Index: packages/analyzer/lib/src/dart/sdk/sdk.dart
diff --git a/packages/analyzer/lib/src/dart/sdk/sdk.dart b/packages/analyzer/lib/src/dart/sdk/sdk.dart
new file mode 100644
index 0000000000000000000000000000000000000000..dbf811c7c01b1df326812e8ab4b61baa542adab7
--- /dev/null
+++ b/packages/analyzer/lib/src/dart/sdk/sdk.dart
@@ -0,0 +1,886 @@
+// Copyright (c) 2016, 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.generated.sdk2;
+
+import 'dart:collection';
+import 'dart:convert';
+import 'dart:io' as io;
+
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/error/listener.dart';
+import 'package:analyzer/exception/exception.dart';
+import 'package:analyzer/file_system/file_system.dart';
+import 'package:analyzer/file_system/memory_file_system.dart';
+import 'package:analyzer/src/context/context.dart';
+import 'package:analyzer/src/dart/scanner/reader.dart';
+import 'package:analyzer/src/dart/scanner/scanner.dart';
+import 'package:analyzer/src/generated/engine.dart';
+import 'package:analyzer/src/generated/java_engine_io.dart';
+import 'package:analyzer/src/generated/parser.dart';
+import 'package:analyzer/src/generated/sdk.dart';
+import 'package:analyzer/src/generated/source_io.dart';
+import 'package:analyzer/src/summary/idl.dart' show PackageBundle;
+import 'package:analyzer/src/summary/summary_sdk.dart';
+import 'package:path/path.dart' as pathos;
+import 'package:yaml/yaml.dart';
+
+/**
+ * An abstract implementation of a Dart SDK in which the available libraries are
+ * stored in a library map. Subclasses are responsible for populating the
+ * library map.
+ */
+abstract class AbstractDartSdk implements DartSdk {
+  /**
+   * The resource provider used to access the file system.
+   */
+  ResourceProvider resourceProvider;
+
+  /**
+   * A mapping from Dart library URI's to the library represented by that URI.
+   */
+  LibraryMap libraryMap = new LibraryMap();
+
+  /**
+   * The [AnalysisOptions] to use to create the [context].
+   */
+  AnalysisOptions _analysisOptions;
+
+  /**
+   * The flag that specifies whether an SDK summary should be used. This is a
+   * temporary flag until summaries are enabled by default.
+   */
+  bool _useSummary = false;
+
+  /**
+   * The [AnalysisContext] which is used for all of the sources in this SDK.
+   */
+  InternalAnalysisContext _analysisContext;
+
+  /**
+   * The mapping from Dart URI's to the corresponding sources.
+   */
+  Map<String, Source> _uriToSourceMap = new HashMap<String, Source>();
+
+  PackageBundle _sdkBundle;
+
+  /**
+   * Set the [options] for this SDK analysis context.  Throw [StateError] if the
+   * context has been already created.
+   */
+  void set analysisOptions(AnalysisOptions options) {
+    if (_analysisContext != null) {
+      throw new StateError(
+          'Analysis options cannot be changed after context creation.');
+    }
+    _analysisOptions = options;
+  }
+
+  @override
+  AnalysisContext get context {
+    if (_analysisContext == null) {
+      _analysisContext = new SdkAnalysisContext(_analysisOptions);
+      SourceFactory factory = new SourceFactory([new DartUriResolver(this)]);
+      _analysisContext.sourceFactory = factory;
+      if (_useSummary) {
+        bool strongMode = _analysisOptions?.strongMode ?? false;
+        PackageBundle sdkBundle = getLinkedBundle();
+        if (sdkBundle != null) {
+          _analysisContext.resultProvider = new SdkSummaryResultProvider(
+              _analysisContext, sdkBundle, strongMode);
+        }
+      }
+    }
+    return _analysisContext;
+  }
+
+  @override
+  List<SdkLibrary> get sdkLibraries => libraryMap.sdkLibraries;
+
+  /**
+   * Return the path separator used by the resource provider.
+   */
+  String get separator => resourceProvider.pathContext.separator;
+
+  @override
+  List<String> get uris => libraryMap.uris;
+
+  /**
+   * Return `true` if the SDK summary will be used when available.
+   */
+  bool get useSummary => _useSummary;
+
+  /**
+   * Specify whether SDK summary should be used.
+   */
+  void set useSummary(bool use) {
+    if (_analysisContext != null) {
+      throw new StateError(
+          'The "useSummary" flag cannot be changed after context creation.');
+    }
+    _useSummary = use;
+  }
+
+  /**
+   * Add the extensions from one or more sdk extension files to this sdk. The
+   * [extensions] should be a table mapping the names of extensions to the paths
+   * where those extensions can be found.
+   */
+  void addExtensions(Map<String, String> extensions) {
+    extensions.forEach((String uri, String path) {
+      SdkLibraryImpl library = new SdkLibraryImpl(uri);
+      library.path = path;
+      libraryMap.setLibrary(uri, library);
+    });
+  }
+
+  @override
+  Source fromFileUri(Uri uri) {
+    File file =
+        resourceProvider.getFile(resourceProvider.pathContext.fromUri(uri));
+    String path = _getPath(file);
+    if (path == null) {
+      return null;
+    }
+    try {
+      return file.createSource(Uri.parse(path));
+    } on FormatException catch (exception, stackTrace) {
+      AnalysisEngine.instance.logger.logInformation(
+          "Failed to create URI: $path",
+          new CaughtException(exception, stackTrace));
+    }
+    return null;
+  }
+
+  @override
+  PackageBundle getLinkedBundle() {
+    if (_useSummary) {
+      bool strongMode = _analysisOptions?.strongMode ?? false;
+      _sdkBundle ??= getSummarySdkBundle(strongMode);
+      return _sdkBundle;
+    }
+    return null;
+  }
+
+  String getRelativePathFromFile(File file);
+
+  @override
+  SdkLibrary getSdkLibrary(String dartUri) => libraryMap.getLibrary(dartUri);
+
+  /**
+   * Return the [PackageBundle] for this SDK, if it exists, or `null` otherwise.
+   * This method should not be used outside of `analyzer` and `analyzer_cli`
+   * packages.
+   */
+  PackageBundle getSummarySdkBundle(bool strongMode);
+
+  Source internalMapDartUri(String dartUri) {
+    // TODO(brianwilkerson) Figure out how to unify the implementations in the
+    // two subclasses.
+    String libraryName;
+    String relativePath;
+    int index = dartUri.indexOf('/');
+    if (index >= 0) {
+      libraryName = dartUri.substring(0, index);
+      relativePath = dartUri.substring(index + 1);
+    } else {
+      libraryName = dartUri;
+      relativePath = "";
+    }
+    SdkLibrary library = getSdkLibrary(libraryName);
+    if (library == null) {
+      return null;
+    }
+    String srcPath;
+    if (relativePath.isEmpty) {
+      srcPath = library.path;
+    } else {
+      String libraryPath = library.path;
+      int index = libraryPath.lastIndexOf(separator);
+      if (index == -1) {
+        index = libraryPath.lastIndexOf('/');
+        if (index == -1) {
+          return null;
+        }
+      }
+      String prefix = libraryPath.substring(0, index + 1);
+      srcPath = '$prefix$relativePath';
+    }
+    String filePath = srcPath.replaceAll('/', separator);
+    try {
+      File file = resourceProvider.getFile(filePath);
+      return file.createSource(Uri.parse(dartUri));
+    } on FormatException {
+      return null;
+    }
+  }
+
+  @override
+  Source mapDartUri(String dartUri) {
+    Source source = _uriToSourceMap[dartUri];
+    if (source == null) {
+      source = internalMapDartUri(dartUri);
+      _uriToSourceMap[dartUri] = source;
+    }
+    return source;
+  }
+
+  String _getPath(File file) {
+    List<SdkLibrary> libraries = libraryMap.sdkLibraries;
+    int length = libraries.length;
+    List<String> paths = new List(length);
+    String filePath = getRelativePathFromFile(file);
+    if (filePath == null) {
+      return null;
+    }
+    for (int i = 0; i < length; i++) {
+      SdkLibrary library = libraries[i];
+      String libraryPath = library.path.replaceAll('/', separator);
+      if (filePath == libraryPath) {
+        return library.shortName;
+      }
+      paths[i] = libraryPath;
+    }
+    for (int i = 0; i < length; i++) {
+      SdkLibrary library = libraries[i];
+      String libraryPath = paths[i];
+      int index = libraryPath.lastIndexOf(separator);
+      if (index >= 0) {
+        String prefix = libraryPath.substring(0, index + 1);
+        if (filePath.startsWith(prefix)) {
+          String relPath =
+              filePath.substring(prefix.length).replaceAll(separator, '/');
+          return '${library.shortName}/$relPath';
+        }
+      }
+    }
+    return null;
+  }
+}
+
+/**
+ * An SDK backed by URI mappings derived from an `_embedder.yaml` file.
+ */
+class EmbedderSdk extends AbstractDartSdk {
+  static const String _DART_COLON_PREFIX = 'dart:';
+
+  static const String _EMBEDDED_LIB_MAP_KEY = 'embedded_libs';
+  final Map<String, String> _urlMappings = new HashMap<String, String>();
+
+  PackageBundle _embedderBundle;
+
+  EmbedderSdk(
+      ResourceProvider resourceProvider, Map<Folder, YamlMap> embedderYamls) {
+    this.resourceProvider = resourceProvider;
+    embedderYamls?.forEach(_processEmbedderYaml);
+    if (embedderYamls?.length == 1) {
+      Folder libFolder = embedderYamls.keys.first;
+      _loadEmbedderBundle(libFolder);
+    }
+  }
+
+  @override
+  // TODO(danrubel) Determine SDK version
+  String get sdkVersion => '0';
+
+  /**
+   * The url mappings for this SDK.
+   */
+  Map<String, String> get urlMappings => _urlMappings;
+
+  @override
+  String getRelativePathFromFile(File file) => file.path;
+
+  @override
+  PackageBundle getSummarySdkBundle(bool strongMode) {
+    if (strongMode) {
+      return _embedderBundle;
+    }
+    return null;
+  }
+
+  @override
+  Source internalMapDartUri(String dartUri) {
+    String libraryName;
+    String relativePath;
+    int index = dartUri.indexOf('/');
+    if (index >= 0) {
+      libraryName = dartUri.substring(0, index);
+      relativePath = dartUri.substring(index + 1);
+    } else {
+      libraryName = dartUri;
+      relativePath = "";
+    }
+    SdkLibrary library = getSdkLibrary(libraryName);
+    if (library == null) {
+      return null;
+    }
+    String srcPath;
+    if (relativePath.isEmpty) {
+      srcPath = library.path;
+    } else {
+      String libraryPath = library.path;
+      int index = libraryPath.lastIndexOf(separator);
+      if (index == -1) {
+        index = libraryPath.lastIndexOf('/');
+        if (index == -1) {
+          return null;
+        }
+      }
+      String prefix = libraryPath.substring(0, index + 1);
+      srcPath = '$prefix$relativePath';
+    }
+    String filePath = srcPath.replaceAll('/', separator);
+    try {
+      File file = resourceProvider.getFile(filePath);
+      return file.createSource(Uri.parse(dartUri));
+    } on FormatException {
+      return null;
+    }
+  }
+
+  void _loadEmbedderBundle(Folder libFolder) {
+    File bundleFile = libFolder.parent.getChildAssumingFile('sdk.ds');
+    if (bundleFile.exists) {
+      try {
+        List<int> bytes = bundleFile.readAsBytesSync();
+        _embedderBundle = new PackageBundle.fromBuffer(bytes);
+      } on FileSystemException {}
+    }
+  }
+
+  /**
+   * Install the mapping from [name] to [libDir]/[file].
+   */
+  void _processEmbeddedLibs(String name, String file, Folder libDir) {
+    if (!name.startsWith(_DART_COLON_PREFIX)) {
+      // SDK libraries must begin with 'dart:'.
+      return;
+    }
+    String libPath = libDir.canonicalizePath(file);
+    _urlMappings[name] = libPath;
+    SdkLibraryImpl library = new SdkLibraryImpl(name);
+    library.path = libPath;
+    libraryMap.setLibrary(name, library);
+  }
+
+  /**
+   * Given the 'embedderYamls' from [EmbedderYamlLocator] check each one for the
+   * top level key 'embedded_libs'. Under the 'embedded_libs' key are key value
+   * pairs. Each key is a 'dart:' library uri and each value is a path
+   * (relative to the directory containing `_embedder.yaml`) to a dart script
+   * for the given library. For example:
+   *
+   * embedded_libs:
+   *   'dart:io': '../../sdk/io/io.dart'
+   *
+   * If a key doesn't begin with `dart:` it is ignored.
+   */
+  void _processEmbedderYaml(Folder libDir, YamlMap map) {
+    YamlNode embedded_libs = map[_EMBEDDED_LIB_MAP_KEY];
+    if (embedded_libs is YamlMap) {
+      embedded_libs.forEach((k, v) => _processEmbeddedLibs(k, v, libDir));
+    }
+  }
+}
+
+/**
+ * A Dart SDK installed in a specified directory. Typical Dart SDK layout is
+ * something like...
+ *
+ *     dart-sdk/
+ *        bin/
+ *           dart[.exe]  <-- VM
+ *        lib/
+ *           core/
+ *              core.dart
+ *              ... other core library files ...
+ *           ... other libraries ...
+ *        util/
+ *           ... Dart utilities ...
+ *     Chromium/   <-- Dartium typically exists in a sibling directory
+ */
+class FolderBasedDartSdk extends AbstractDartSdk {
+  /**
+   * The name of the directory within the SDK directory that contains
+   * executables.
+   */
+  static String _BIN_DIRECTORY_NAME = "bin";
+
+  /**
+   * The name of the directory within the SDK directory that contains
+   * documentation for the libraries.
+   */
+  static String _DOCS_DIRECTORY_NAME = "docs";
+
+  /**
+   * The name of the directory within the SDK directory that contains the
+   * sdk_library_metadata directory.
+   */
+  static String _INTERNAL_DIR = "_internal";
+
+  /**
+   * The name of the sdk_library_metadata directory that contains the package
+   * holding the libraries.dart file.
+   */
+  static String _SDK_LIBRARY_METADATA_DIR = "sdk_library_metadata";
+
+  /**
+   * The name of the directory within the sdk_library_metadata that contains
+   * libraries.dart.
+   */
+  static String _SDK_LIBRARY_METADATA_LIB_DIR = "lib";
+
+  /**
+   * The name of the directory within the SDK directory that contains the
+   * libraries.
+   */
+  static String _LIB_DIRECTORY_NAME = "lib";
+
+  /**
+   * The name of the libraries file.
+   */
+  static String _LIBRARIES_FILE = "libraries.dart";
+
+  /**
+   * The name of the pub executable on windows.
+   */
+  static String _PUB_EXECUTABLE_NAME_WIN = "pub.bat";
+
+  /**
+   * The name of the pub executable on non-windows operating systems.
+   */
+  static String _PUB_EXECUTABLE_NAME = "pub";
+
+  /**
+   * The name of the file within the SDK directory that contains the version
+   * number of the SDK.
+   */
+  static String _VERSION_FILE_NAME = "version";
+
+  /**
+   * The directory containing the SDK.
+   */
+  Folder _sdkDirectory;
+
+  /**
+   * The directory within the SDK directory that contains the libraries.
+   */
+  Folder _libraryDirectory;
+
+  /**
+   * The revision number of this SDK, or `"0"` if the revision number cannot be
+   * discovered.
+   */
+  String _sdkVersion;
+
+  /**
+   * The file containing the pub executable.
+   */
+  File _pubExecutable;
+
+  /**
+   * Initialize a newly created SDK to represent the Dart SDK installed in the
+   * [sdkDirectory]. The flag [useDart2jsPaths] is `true` if the dart2js path
+   * should be used when it is available
+   */
+  FolderBasedDartSdk(ResourceProvider resourceProvider, this._sdkDirectory,
+      [bool useDart2jsPaths = false]) {
+    this.resourceProvider = resourceProvider;
+    libraryMap = initialLibraryMap(useDart2jsPaths);
+  }
+
+  /**
+   * Return the directory containing the SDK.
+   */
+  Folder get directory => _sdkDirectory;
+
+  /**
+   * Return the directory containing documentation for the SDK.
+   */
+  Folder get docDirectory =>
+      _sdkDirectory.getChildAssumingFolder(_DOCS_DIRECTORY_NAME);
+
+  /**
+   * Return the directory within the SDK directory that contains the libraries.
+   */
+  Folder get libraryDirectory {
+    if (_libraryDirectory == null) {
+      _libraryDirectory =
+          _sdkDirectory.getChildAssumingFolder(_LIB_DIRECTORY_NAME);
+    }
+    return _libraryDirectory;
+  }
+
+  /**
+   * Return the file containing the Pub executable, or `null` if it does not exist.
+   */
+  File get pubExecutable {
+    if (_pubExecutable == null) {
+      _pubExecutable = _sdkDirectory
+          .getChildAssumingFolder(_BIN_DIRECTORY_NAME)
+          .getChildAssumingFile(OSUtilities.isWindows()
+              ? _PUB_EXECUTABLE_NAME_WIN
+              : _PUB_EXECUTABLE_NAME);
+    }
+    return _pubExecutable;
+  }
+
+  /**
+   * Return the revision number of this SDK, or `"0"` if the revision number
+   * cannot be discovered.
+   */
+  @override
+  String get sdkVersion {
+    if (_sdkVersion == null) {
+      _sdkVersion = DartSdk.DEFAULT_VERSION;
+      File revisionFile =
+          _sdkDirectory.getChildAssumingFile(_VERSION_FILE_NAME);
+      try {
+        String revision = revisionFile.readAsStringSync();
+        if (revision != null) {
+          _sdkVersion = revision.trim();
+        }
+      } on FileSystemException {
+        // Fall through to return the default.
+      }
+    }
+    return _sdkVersion;
+  }
+
+  /**
+   * Determine the search order for trying to locate the [_LIBRARIES_FILE].
+   */
+  Iterable<File> get _libraryMapLocations sync* {
+    yield libraryDirectory
+        .getChildAssumingFolder(_INTERNAL_DIR)
+        .getChildAssumingFolder(_SDK_LIBRARY_METADATA_DIR)
+        .getChildAssumingFolder(_SDK_LIBRARY_METADATA_LIB_DIR)
+        .getChildAssumingFile(_LIBRARIES_FILE);
+    yield libraryDirectory
+        .getChildAssumingFolder(_INTERNAL_DIR)
+        .getChildAssumingFile(_LIBRARIES_FILE);
+  }
+
+  @override
+  String getRelativePathFromFile(File file) {
+    String filePath = file.path;
+    String libPath = libraryDirectory.path;
+    if (!filePath.startsWith("$libPath$separator")) {
+      return null;
+    }
+    return filePath.substring(libPath.length + 1);
+  }
+
+  /**
+   * Return the [PackageBundle] for this SDK, if it exists, or `null` otherwise.
+   * This method should not be used outside of `analyzer` and `analyzer_cli`
+   * packages.
+   */
+  PackageBundle getSummarySdkBundle(bool strongMode) {
+    String rootPath = directory.path;
+    String name = strongMode ? 'strong.sum' : 'spec.sum';
+    String path =
+        resourceProvider.pathContext.join(rootPath, 'lib', '_internal', name);
+    try {
+      File file = resourceProvider.getFile(path);
+      if (file.exists) {
+        List<int> bytes = file.readAsBytesSync();
+        return new PackageBundle.fromBuffer(bytes);
+      }
+    } catch (exception, stackTrace) {
+      AnalysisEngine.instance.logger.logError(
+          'Failed to load SDK analysis summary from $path',
+          new CaughtException(exception, stackTrace));
+    }
+    return null;
+  }
+
+  /**
+   * Read all of the configuration files to initialize the library maps. The
+   * flag [useDart2jsPaths] is `true` if the dart2js path should be used when it
+   * is available. Return the initialized library map.
+   */
+  LibraryMap initialLibraryMap(bool useDart2jsPaths) {
+    List<String> searchedPaths = <String>[];
+    var lastStackTrace = null;
+    var lastException = null;
+    for (File librariesFile in _libraryMapLocations) {
+      try {
+        String contents = librariesFile.readAsStringSync();
+        return new SdkLibrariesReader(useDart2jsPaths)
+            .readFromFile(librariesFile, contents);
+      } catch (exception, stackTrace) {
+        searchedPaths.add(librariesFile.path);
+        lastException = exception;
+        lastStackTrace = stackTrace;
+      }
+    }
+    StringBuffer buffer = new StringBuffer();
+    buffer.writeln('Could not initialize the library map from $searchedPaths');
+    if (resourceProvider is MemoryResourceProvider) {
+      (resourceProvider as MemoryResourceProvider).writeOn(buffer);
+    }
+    AnalysisEngine.instance.logger.logError(
+        buffer.toString(), new CaughtException(lastException, lastStackTrace));
+    return new LibraryMap();
+  }
+
+  @override
+  Source internalMapDartUri(String dartUri) {
+    String libraryName;
+    String relativePath;
+    int index = dartUri.indexOf('/');
+    if (index >= 0) {
+      libraryName = dartUri.substring(0, index);
+      relativePath = dartUri.substring(index + 1);
+    } else {
+      libraryName = dartUri;
+      relativePath = "";
+    }
+    SdkLibrary library = getSdkLibrary(libraryName);
+    if (library == null) {
+      return null;
+    }
+    try {
+      File file = libraryDirectory.getChildAssumingFile(library.path);
+      if (!relativePath.isEmpty) {
+        file = file.parent.getChildAssumingFile(relativePath);
+      }
+      return file.createSource(Uri.parse(dartUri));
+    } on FormatException {
+      return null;
+    }
+  }
+
+  /**
+   * Return the default directory for the Dart SDK, or `null` if the directory
+   * cannot be determined (or does not exist). The default directory is provided
+   * by a system property named `com.google.dart.sdk`.
+   */
+  static Folder defaultSdkDirectory(ResourceProvider resourceProvider) {
+    // TODO(brianwilkerson) This is currently only being used in the analysis
+    // server's Driver class to find the default SDK. The command-line analyzer
+    // uses cli_utils to find the SDK. Not sure why they're different.
+    String sdkProperty = getSdkProperty(resourceProvider);
+    if (sdkProperty == null) {
+      return null;
+    }
+    Folder sdkDirectory = resourceProvider.getFolder(sdkProperty);
+    if (!sdkDirectory.exists) {
+      return null;
+    }
+    return sdkDirectory;
+  }
+
+  static String getSdkProperty(ResourceProvider resourceProvider) {
+    String exec = io.Platform.resolvedExecutable;
+    if (exec.length == 0) {
+      return null;
+    }
+    pathos.Context pathContext = resourceProvider.pathContext;
+    if (pathContext.style != pathos.context.style) {
+      // This will only be true if pathContext == posix and
+      // pathos.context == windows, which only happens when running tests.
+      if (exec.startsWith(new RegExp('[a-zA-Z]:'))) {
+        exec = exec.substring(2);
+      }
+      exec = pathContext.fromUri(pathos.context.toUri(exec));
+    }
+    // Might be "xcodebuild/ReleaseIA32/dart" with "sdk" sibling
+    String outDir = pathContext.dirname(pathContext.dirname(exec));
+    String sdkPath = pathContext.join(pathContext.dirname(outDir), "sdk");
+    if (resourceProvider.getFolder(sdkPath).exists) {
+      return sdkPath;
+    }
+    // probably be "dart-sdk/bin/dart"
+    return pathContext.dirname(pathContext.dirname(exec));
+  }
+}
+
+/**
+ * An object used to locate SDK extensions.
+ *
+ * Given a package map, it will check in each package's `lib` 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 a path (relative
+ * to the directory containing `_sdkext`) to a dart script 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 SdkExtensionFinder {
+  /**
+   * The name of the extension file.
+   */
+  static const String SDK_EXT_NAME = '_sdkext';
+
+  /**
+   * The prefix required for all keys in an extension file that will not be
+   * ignored.
+   */
+  static const String DART_COLON_PREFIX = 'dart:';
+
+  /**
+   * A table mapping the names of extensions to the paths where those extensions
+   * can be found.
+   */
+  final Map<String, String> _urlMappings = <String, String>{};
+
+  /**
+   * The absolute paths of the extension files that contributed to the
+   * [_urlMappings].
+   */
+  final List<String> extensionFilePaths = <String>[];
+
+  /**
+   * Initialize a newly created finder to look in the packages in the given
+   * [packageMap] for SDK extension files.
+   */
+  SdkExtensionFinder(Map<String, List<Folder>> packageMap) {
+    if (packageMap == null) {
+      return;
+    }
+    packageMap.forEach(_processPackage);
+  }
+
+  /**
+   * Return a table mapping the names of extensions to the paths where those
+   * extensions can be found.
+   */
+  Map<String, String> get urlMappings =>
+      new Map<String, String>.from(_urlMappings);
+
+  /**
+   * Given a package [name] and a list of folders ([libDirs]), add any found sdk
+   * extensions.
+   */
+  void _processPackage(String name, List<Folder> libDirs) {
+    for (var libDir in libDirs) {
+      var sdkExt = _readDotSdkExt(libDir);
+      if (sdkExt != null) {
+        _processSdkExt(sdkExt, libDir);
+      }
+    }
+  }
+
+  /**
+   * Given the JSON for an SDK extension ([sdkExtJSON]) and a folder ([libDir]),
+   * 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;
+    }
+    bool contributed = false;
+    sdkExt.forEach((k, v) {
+      if (k is String && v is String && _processSdkExtension(libDir, k, v)) {
+        contributed = true;
+      }
+    });
+    if (contributed) {
+      extensionFilePaths.add(libDir.getChild(SDK_EXT_NAME).path);
+    }
+  }
+
+  /**
+   * Install the mapping from [name] to [libDir]/[file].
+   */
+  bool _processSdkExtension(Folder libDir, String name, String file) {
+    if (!name.startsWith(DART_COLON_PREFIX)) {
+      // SDK extensions must begin with 'dart:'.
+      return false;
+    }
+    _urlMappings[name] = libDir.canonicalizePath(file);
+    return true;
+  }
+
+  /**
+   * Read the contents of [libDir]/[SDK_EXT_NAME] as a string, or `null` if the
+   * file doesn't exist.
+   */
+  String _readDotSdkExt(Folder libDir) {
+    File file = libDir.getChild(SDK_EXT_NAME);
+    try {
+      return file.readAsStringSync();
+    } on FileSystemException {
+      // File can't be read.
+      return null;
+    }
+  }
+}
+
+/**
+ * An object used to read and parse the libraries file
+ * (dart-sdk/lib/_internal/sdk_library_metadata/lib/libraries.dart) for information
+ * about the libraries in an SDK. The library information is represented as a
+ * Dart file containing a single top-level variable whose value is a const map.
+ * The keys of the map are the names of libraries defined in the SDK and the
+ * values in the map are info objects defining the library. For example, a
+ * subset of a typical SDK might have a libraries file that looks like the
+ * following:
+ *
+ *     final Map<String, LibraryInfo> LIBRARIES = const <LibraryInfo> {
+ *       // Used by VM applications
+ *       "builtin" : const LibraryInfo(
+ *         "builtin/builtin_runtime.dart",
+ *         category: "Server",
+ *         platforms: VM_PLATFORM),
+ *
+ *       "compiler" : const LibraryInfo(
+ *         "compiler/compiler.dart",
+ *         category: "Tools",
+ *         platforms: 0),
+ *     };
+ */
+class SdkLibrariesReader {
+  /**
+   * A flag indicating whether the dart2js path should be used when it is
+   * available.
+   */
+  final bool _useDart2jsPaths;
+
+  /**
+   * Initialize a newly created library reader to use the dart2js path if
+   * [_useDart2jsPaths] is `true`.
+   */
+  SdkLibrariesReader(this._useDart2jsPaths);
+
+  /**
+   * Return the library map read from the given [file], given that the content
+   * of the file is already known to be [libraryFileContents].
+   */
+  LibraryMap readFromFile(File file, String libraryFileContents) =>
+      readFromSource(file.createSource(), libraryFileContents);
+
+  /**
+   * Return the library map read from the given [source], given that the content
+   * of the file is already known to be [libraryFileContents].
+   */
+  LibraryMap readFromSource(Source source, String libraryFileContents) {
+    BooleanErrorListener errorListener = new BooleanErrorListener();
+    Scanner scanner = new Scanner(
+        source, new CharSequenceReader(libraryFileContents), errorListener);
+    Parser parser = new Parser(source, errorListener);
+    CompilationUnit unit = parser.parseCompilationUnit(scanner.tokenize());
+    SdkLibrariesReader_LibraryBuilder libraryBuilder =
+        new SdkLibrariesReader_LibraryBuilder(_useDart2jsPaths);
+    // If any syntactic errors were found then don't try to visit the AST
+    // structure.
+    if (!errorListener.errorReported) {
+      unit.accept(libraryBuilder);
+    }
+    return libraryBuilder.librariesMap;
+  }
+}