Move SdkExtUriResolver from analysis_server to analyzer so it can be used in analyzer_cli

pkg/analysis_server/lib/src/sdk_ext.dart

-// 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: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;
-
-class _SdkExtFileBasedSource extends FileBasedSource {
-  _SdkExtFileBasedSource(JavaFile file, Uri uri)
-      : super(file, uri);
-}
-
-/// 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 _SdkExtFileBasedSource(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 _SdkExtFileBasedSource(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) {
-    if (source is _SdkExtFileBasedSource) {
-      return source.uri;
-    }
-    return null;
-  }
-
-  /// 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;
-  }
-}