Initial --modules=es6 support

lib/src/options.dart

Index: lib/src/options.dart
diff --git a/lib/src/options.dart b/lib/src/options.dart
index cf6aaa6300b91ade67cf0ac39fb50c3b3b99c870..ca6e1c75a53a388353e2e002aa393f6a820b3487 100644
--- a/lib/src/options.dart
+++ b/lib/src/options.dart
@@ -56,6 +56,11 @@ class SourceResolverOptions {
       this.useImplicitHtml: false});
 }
 
+enum ModuleFormat { es6, dart }

[Jennifer Messerly, 2016/01/22 18:29:01]

Heh, not sure the enum adds much value. More an issue with Dart enums, though.

e.g. with a custom enum class, we could add a method that knows how to
instantiate the right module builder, for example. And we wouldn't need to make
its internal name exactly match its option representation. And the parse method
wouldn't need to live as another top-level name.

But, we'd lose out on the static checking that all cases are covered in switch,
maybe.

So, not sure this is worth changing. Just throwing that out there for
discussion. :)

[ochafik, 2016/01/23 12:24:18]

I agree, *if only* we had Java enums...

+
+ModuleFormat parseModuleFormat(String s) =>
+    ModuleFormat.values.firstWhere((v) => s == '$v'.split('.')[1]);

[Jennifer Messerly, 2016/01/22 18:29:01]

if parsing fails, are we okay because args option parser will have already
issued a nice error message before we get to this point?

[ochafik, 2016/01/23 12:24:18]

Yes we are, but cleaned up utils (moved to utils.dart) + added tests to stay on
the safe side.

+
 // TODO(jmesserly): refactor all codegen options here.
 class CodegenOptions {
   /// Whether to emit the source map files.
@@ -79,7 +84,7 @@ class CodegenOptions {
 
   /// Which module format to support.
   /// Currently 'es6' and 'dart' are supported.
-  final String moduleFormat;
+  final ModuleFormat moduleFormat;
 
   const CodegenOptions(
       {this.emitSourceMaps: true,
@@ -88,7 +93,7 @@ class CodegenOptions {
       this.destructureNamedParams: _DESTRUCTURE_NAMED_PARAMS_DEFAULT,
       this.outputDir,
       this.arrowFnBindThisWorkaround: false,
-      this.moduleFormat: 'dart'});
+      this.moduleFormat: ModuleFormat.dart});
 }
 
 /// Options for devrun.
@@ -158,7 +163,7 @@ class CompilerOptions {
   /// to this directory.
   final String inputBaseDir;
 
-  CompilerOptions(
+  const CompilerOptions(
       {this.sourceOptions: const SourceResolverOptions(),
       this.codegenOptions: const CodegenOptions(),
       this.runnerOptions: const RunnerOptions(),
@@ -239,7 +244,7 @@ CompilerOptions parseOptions(List<String> argv, {bool forceOutDir: false}) {
           destructureNamedParams: args['destructure-named-params'],
           outputDir: outputDir,
           arrowFnBindThisWorkaround: args['arrow-fn-bind-this'],
-          moduleFormat: args['modules']),
+          moduleFormat: parseModuleFormat(args['modules'])),
       sourceOptions: new SourceResolverOptions(
           useMockSdk: args['mock-sdk'],
           dartSdkPath: sdkPath,
@@ -309,7 +314,7 @@ final ArgParser argParser = new ArgParser()
       allowed: ['es6', 'dart'],
       allowedHelp: {
         'es6': 'es6 modules',
-        'custom-dart': 'a custom format used by dartdevc, similar to AMD'
+        'dart': 'a custom format used by dartdevc, similar to AMD'

[Jennifer Messerly, 2016/01/22 18:29:01]

Hmmm, I don't like calling this format "dart" ... as it implies Dart needs its
own module format, or something.
Perhaps "legacy", to make it clear this is historical baggage?

[ochafik, 2016/01/23 12:24:17]

Done (+ tied these values to the enum with a getEnumName)

       },
       defaultsTo: 'dart')