fixes #201, add support for custom URL mapping

lib/src/options.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.
 
 /// Set of flags and options passed to the compiler
 library dev_compiler.src.options;
 
 import 'dart:io';
 
 import 'package:args/args.dart';
@@ skipping 218 matching lines @@
 
   /// Whether to emit the source map files.
   @override
   final bool emitSourceMaps;
 
   /// Location for runtime files, such as `dart_runtime.js`. By default this is
   /// inferred to be under `lib/runtime/` in the location of the `dev_compiler`
   /// package (if we can infer where that is located).
   final String runtimeDir;
 
+  /// Custom URI mappings, such as "dart:foo" -> "path/to/foo.dart"
+  final Map<String, String> customUrlMappings;
+
   CompilerOptions({this.allowConstCasts: true, this.checkSdk: false,
       this.dumpInfo: false, this.dumpInfoFile, this.dumpSrcDir,
       this.forceCompile: false, this.formatOutput: false,
       this.ignoreTypes: false,
       this.wrapClosures: RulesOptions.wrapClosuresDefault, this.outputDir,
       this.outputDart: false, this.useColors: true,
       this.covariantGenerics: true, this.relaxedCasts: true,
       this.useMultiPackage: false, this.packageRoot: 'packages/',
       this.packagePaths: const <String>[], this.resources: const <String>[],
       this.inferDownwards: RulesOptions.inferDownwardsDefault,
       this.inferFromOverrides: ResolverOptions.inferFromOverridesDefault,
       this.inferTransitively: ResolverOptions.inferTransitivelyDefault,
       this.onlyInferConstsAndFinalFields: ResolverOptions.onlyInferConstAndFinalFieldsDefault,
       this.nonnullableTypes: TypeOptions.NONNULLABLE_TYPES, this.help: false,
       this.useMockSdk: false, this.dartSdkPath, this.logLevel: Level.SEVERE,
       this.emitSourceMaps: true, this.entryPointFile: null,
       this.serverMode: false, this.useImplicitHtml: false,
       this.enableHashing: false, this.host: 'localhost', this.port: 8080,
-      this.runtimeDir});
+      this.runtimeDir, this.customUrlMappings: const {}});
 }
 
 /// Parses options from the command-line
 CompilerOptions parseOptions(List<String> argv) {
   ArgResults args = argParser.parse(argv);
+  bool showUsage = args['help'];
+
   var serverMode = args['server'];
   var enableHashing = args['hashing'];
   if (enableHashing == null) {
     enableHashing = serverMode;
   }
   // TODO(jmesserly): shouldn't level always default to warning?
   var logLevel = serverMode ? Level.WARNING : Level.SEVERE;
   var levelName = args['log'];
   if (levelName != null) {
     levelName = levelName.toUpperCase();
     logLevel = Level.LEVELS.firstWhere((l) => l.name == levelName,
         orElse: () => logLevel);
   }
   var useColors = stdioType(stdout) == StdioType.TERMINAL;
   var sdkPath = args['dart-sdk'];
   if (sdkPath == null && !args['mock-sdk']) {
     sdkPath = getSdkDir(argv).path;
   }
   var runtimeDir = args['runtime-dir'];
   if (runtimeDir == null) {
     runtimeDir = _computeRuntimeDir();
   }
   var outputDir = args['out'];
   if (outputDir == null && serverMode) {
     outputDir = Directory.systemTemp.createTempSync("dev_compiler_out_").path;
   }
   var dumpInfo = args['dump-info'];
   if (dumpInfo == null) dumpInfo = serverMode;
 
+  var customUrlMappings = <String, String>{};
+  for (var mapping in args['url-mapping']) {
+    var splitMapping = mapping.split(',');
+    if (splitMapping.length != 2) {
+      showUsage = true;
+      continue;
+    }
+    customUrlMappings[splitMapping[0]] = splitMapping[1];
+  }
+
   var entryPointFile = args.rest.length == 0 ? null : args.rest.first;
 
   return new CompilerOptions(
       allowConstCasts: args['allow-const-casts'],
       checkSdk: args['sdk-check'],
       dumpInfo: dumpInfo,
       dumpInfoFile: args['dump-info-file'],
       dumpSrcDir: args['dump-src-to'],
       forceCompile: args['force-compile'] || serverMode,
       formatOutput: args['dart-gen-fmt'],
       ignoreTypes: args['ignore-types'],
       wrapClosures: args['wrap-closures'],
       outputDart: args['dart-gen'],
       outputDir: outputDir,
       covariantGenerics: args['covariant-generics'],
       relaxedCasts: args['relaxed-casts'],
       useColors: useColors,
+      customUrlMappings: customUrlMappings,
       useMultiPackage: args['use-multi-package'],
       packageRoot: args['package-root'],
       packagePaths: args['package-paths'].split(','),
       resources: args['resources']
           .split(',')
           .where((s) => s.isNotEmpty)
           .toList(),
       inferDownwards: args['infer-downwards'],
       inferFromOverrides: args['infer-from-overrides'],
       inferTransitively: args['infer-transitively'],
       onlyInferConstsAndFinalFields: args['infer-only-finals'],
       nonnullableTypes: optionsToList(args['nonnullable'],
           defaultValue: TypeOptions.NONNULLABLE_TYPES),
-      help: args['help'],
+      help: showUsage,
       useMockSdk: args['mock-sdk'],
       dartSdkPath: sdkPath,
       logLevel: logLevel,
       emitSourceMaps: args['source-maps'],
       entryPointFile: entryPointFile,
       serverMode: serverMode,
       useImplicitHtml: serverMode && entryPointFile.endsWith('.dart'),
       enableHashing: enableHashing,
       host: args['host'],
       port: int.parse(args['port']),
@@ skipping 40 matching lines @@
   ..addOption('dart-sdk', help: 'Dart SDK Path', defaultsTo: null)
   ..addFlag('dart-gen',
       abbr: 'd', help: 'Generate dart output', defaultsTo: false)
   ..addFlag('dart-gen-fmt',
       help: 'Generate readable dart output', defaultsTo: true)
   ..addOption('dump-src-to', help: 'Dump dart src code', defaultsTo: null)
   ..addOption('package-root',
       abbr: 'p',
       help: 'Package root to resolve "package:" imports',
       defaultsTo: 'packages/')
+  ..addOption('url-mapping',
+      help: '--url-mapping=libraryUri,/path/to/library.dart uses library.dart\n'
+      'as the source for an import of of "libraryUri".',
+      allowMultiple: true,
+      splitCommas: false)
   ..addFlag('use-multi-package',
       help: 'Whether to use the multi-package resolver for "package:" imports',
       defaultsTo: false)
   ..addOption('package-paths',
       help: 'if using the multi-package resolver, the list of directories to\n'
       'look for packages in.', defaultsTo: '')
   ..addOption('resources',
       help: 'Additional resources to serve', defaultsTo: '')
   ..addFlag('source-maps',
       help: 'Whether to emit source map files', defaultsTo: true)
@@ skipping 65 matching lines @@
     // The pub-cache directory is two levels up, but we verify that the layout
     // looks correct.
     if (path.basename(dir) != 'dev_compiler') return null;
     dir = path.dirname(dir);
     if (path.basename(dir) != 'global_packages') return null;
     dir = path.dirname(dir);
     return path.join(dir, cacheDir, 'lib', 'runtime');
   }
   return null;
 }