First shot at source maps generation in dart2js.

lib/compiler/compiler.dart

Index: lib/compiler/compiler.dart
diff --git a/lib/compiler/compiler.dart b/lib/compiler/compiler.dart
index 4038fad3606ba13f5963af77807f6fcf7c9e30ca..3eb2d359fc251f79639a7c002019415c27a2ff93 100644
--- a/lib/compiler/compiler.dart
+++ b/lib/compiler/compiler.dart
@@ -6,6 +6,8 @@
 
 #import('dart:uri');
 #import('implementation/apiimpl.dart');
+#import('implementation/source_file.dart');
+#import('implementation/util/source_map_builder.dart');
 
 // Unless explicitly allowed, passing null for any argument to the
 // methods of library will result in a NullPointerException being
@@ -31,20 +33,29 @@ typedef Future<String> ReadUriFromString(Uri uri);
 typedef void DiagnosticHandler(Uri uri, int begin, int end,
                                String message, bool fatal);
 
+class CompiledScript {

[podivilov, 2012/06/19 16:37:54]

This is ugly, not sure how to return sourceMap from compile. class Compilation
suggested by Bob may help here.

[ahe, 2012/06/19 17:00:41]

Yes. Johnni will handle that.

In the meantime, how about using a custom Diagnostic (new API I just added)?

I would really prefer if we avoid modifying this file.

[podivilov, 2012/06/20 09:37:14]

Done.

+  String code;
+  String sourceMap;
+  CompiledScript(this.code, this.sourceMap);
+}
+
 /**
  * Returns [script] compiled to JavaScript. If the compilation fails,
  * null is returned and [handler] will have been invoked at least once
  * with [:fatal == true:].
  */
-Future<String> compile(Uri script,
-                       Uri libraryRoot,
-                       Uri packageRoot,
-                       ReadUriFromString provider,
-                       DiagnosticHandler handler,
-                       [List<String> options = const []]) {
+Future<CompiledScript> compile(Uri script,
+                               Uri libraryRoot,
+                               Uri packageRoot,
+                               ReadUriFromString provider,
+                               DiagnosticHandler handler,
+                               [List<String> options = const []]) {
   Compiler compiler = new Compiler(provider, handler, libraryRoot, packageRoot,
                                    options);
   compiler.run(script);
   String code = compiler.assembledCode;
-  return new Future.immediate(code);
+  SourceFile compiledFile = new SourceFile(null, code);

[podivilov, 2012/06/19 16:37:54]

We could pass SourceMapListener interface/handler to compile and remove source
map building details from this path. WDYT?

+  String sourceMap = new SourceMapBuilder().build(

[ahe, 2012/06/19 17:00:41]

This code does not belong here. I think the source map should be created by
emitter.assembleProgram(). I would communicate the result back to dart2js.dart
by adding something like this to the end of assembleProgram:

compiler.reportDiagnostic(null, new SourceMapBuilder().build(sourceMappings),
new api.Diagnostic(-1, 'source map'));

[podivilov, 2012/06/20 09:37:14]

Done.

+      compiler.backend.emitter.sourceMappings, compiledFile);
+  return new Future.immediate(new CompiledScript(code, sourceMap));
 }