First shot at source maps generation in dart2js.

lib/compiler/implementation/dart2js.dart

Index: lib/compiler/implementation/dart2js.dart
diff --git a/lib/compiler/implementation/dart2js.dart b/lib/compiler/implementation/dart2js.dart
index 2bfd2c0c79d3edf4381cc603809b7203e3c86ca3..04ba44abd5e27b2adcb6853dcce3ee0f60da0b92 100644
--- a/lib/compiler/implementation/dart2js.dart
+++ b/lib/compiler/implementation/dart2js.dart
@@ -71,6 +71,7 @@ void compile(List<String> argv) {
   bool verbose = false;
   Uri libraryRoot = cwd;
   Uri out = cwd.resolve('out.js');
+  Uri sourceMapOut = null;
   Uri packageRoot = null;
   List<String> options = new List<String>();
   bool explicitOut = false;
@@ -92,6 +93,11 @@ void compile(List<String> argv) {
     out = cwd.resolve(nativeToUriPath(extractParameter(argument)));
   }
 
+  setSourceMapOutput(String argument) {
+    sourceMapOut = cwd.resolve(nativeToUriPath(extractParameter(argument)));
+    passThrough(argument);
+  }
+
   handleShortOptions(String argument) {
     var shortOptions = argument.substring(1).splitChars();
     for (var shortOption in shortOptions) {
@@ -121,6 +127,7 @@ void compile(List<String> argv) {
     new OptionHandler('--verbose', (_) => verbose = true),
     new OptionHandler('--library-root=.+', setLibraryRoot),
     new OptionHandler('--out=.+|-o.+', setOutput),
+    new OptionHandler('--source-map-out=.+', setSourceMapOutput),

[ahe, 2012/06/20 11:56:59]

I just talked to the bigwigs. We want to turn on source maps always. So we don't
need an option.

[podivilov, 2012/06/20 14:15:15]

Done.

     new OptionHandler('--allow-mock-compilation', passThrough),
     new OptionHandler('--unparse-validation', passThrough),
     new OptionHandler('--no-colors', (_) => enableColors = false),
@@ -181,6 +188,13 @@ void compile(List<String> argv) {
 
   void handler(Uri uri, int begin, int end, String message,
                api.Diagnostic kind) {
+    if (kind.name === 'source map') {
+      // TODO(podivilov): We should find a better way to return source maps from
+      // emitter. Using diagnostic handler for that purpose is a temporary hack.
+      writeString(sourceMapOut, message);
+      return;
+    }
+
     if (isAborting) return;
     isAborting = kind === api.Diagnostic.CRASH;
     bool fatal = (kind.ordinal & FATAL) != 0;
@@ -228,11 +242,14 @@ void compile(List<String> argv) {
 
   // TODO(ahe): We expect the future to be complete and call value
   // directly. In effect, we don't support truly asynchronous API.
-  String code = api.compile(uri, libraryRoot, packageRoot, provider, handler,
-                            options).value;
+  String code = api.compile(
+      uri, libraryRoot, packageRoot, provider, handler, options).value;

[ahe, 2012/06/20 11:56:59]

This change seem unnecessary.

[podivilov, 2012/06/20 14:15:15]

Done.

   if (code === null) {
     fail('Error: Compilation failed.');
   }
+  if (sourceMapOut !== null) {
+    code = '$code\n//@ sourceMappingURL=$sourceMapOut';
+  }
   writeString(out, code);
   int jsBytesWritten = code.length;
   info('compiled $dartBytesRead bytes Dart -> $jsBytesWritten bytes JS '