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..868c81117fd19c1af25bf566b3f2bd2209c027d8
--- /dev/null
+++ b/pkg/analysis_server/lib/src/sdk_ext.dart
@@ -0,0 +1,160 @@
+// 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 analysis_server.src.sdk_ext;
+
+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';
+import 'package:analyzer/src/generated/java_io.dart' show JavaFile;
+import 'package:analyzer/src/generated/source_io.dart' show FileBasedSource;
+import 'package:path/path.dart' as pathos;
+
+/// Given a packageMap (see [PackageMapProvider]), 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 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>{};
+
+  /// Construct a [SdkExtUriResolver] from a package map
+  /// (see [PackageMapProvider]).
+  SdkExtUriResolver(Map<String, List<Folder>> packageMap) {
+    if (packageMap == null) {
+      return;
+    }
+    packageMap.forEach(_processPackage);
+  }
+
+  /// Programmatically add a new SDK extension given a JSON description
+  /// ([sdkExtJSON]) and a lib directory ([libDir]).
+  void addSdkExt(String sdkExtJSON, Folder libDir) {
+    _processSdkExt(sdkExtJSON, libDir);
+  }
+
+  /// Return the path mapping for [libName] or null if there is none.
+  String operator[](String libName) => _urlMappings[libName];
+
+  /// Number of sdk extensions.
+  int get length => _urlMappings.length;
+
+  /// Resolve a 'part' statement inside an sdk extension.
+  Source _resolvePart(Uri libraryEntry, String partPath, Uri importUri) {
+    // Library part.
+    var directory = pathos.dirname(libraryEntry.path);
+    var partUri = new Uri.file(pathos.join(directory, partPath));
+    assert(partUri.isAbsolute);
+    JavaFile javaFile = new JavaFile.fromUri(partUri);
+    return new FileBasedSource(javaFile, importUri);
+  }
+
+  /// Resolve an import of an sdk extension.
+  Source _resolveEntry(Uri libraryEntry, Uri importUri) {
+    // Library entry.
+    JavaFile javaFile = new JavaFile.fromUri(libraryEntry);
+    return new FileBasedSource(javaFile, importUri);
+  }
+
+  @override
+  Source resolveAbsolute(Uri importUri) {
+    // Split import uri into library name and (optionally) a part path.
+    var uri = importUri.toString();
+    String libraryName;
+    String partPath;
+    int index = uri.indexOf('/');
+    if (index >= 0) {
+      libraryName = uri.substring(0, index);
+      partPath = uri.substring(index + 1);
+    } else {
+      libraryName = uri;
+    }
+    // Lookup library name in mappings.
+    String mapping = _urlMappings[libraryName];
+    if (mapping == null) {
+      // Not found.
+      return null;
+    }
+    // This mapping points to the main entry file of the sdk extension.
+    Uri libraryEntry = new Uri.file(mapping);
+    if (!libraryEntry.isAbsolute) {
+      // We expect an absolute path.
+      return null;
+    }
+
+    if (index >= 0) {
+      return _resolvePart(libraryEntry, partPath, importUri);
+    } else {
+      return _resolveEntry(libraryEntry, importUri);
+    }
+  }
+
+  @override
+  Uri restoreAbsolute(Source source) {
+    return source.uri;
+  }
+
+  /// 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);
+      }
+    }
+  }
+
+  /// 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 ([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;
+    }
+    sdkExt.forEach((k, v) => _processSdkExtension(k, v, libDir));
+  }
+
+  /// Install the mapping from [name] to [libDir]/[file].
+  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;
+  }
+}