First shot at source maps generation in dart2js.

lib/compiler/compiler.dart

 // Copyright (c) 2012, 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('compiler');
 
 #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
 // thrown.
 
 /**
  * Returns the source corresponding to [uri]. If no such source exists
  * or if an error occur while fetching it, this method must throw an
  * exception.
  */
 typedef Future<String> ReadUriFromString(Uri uri);
 
 /**
  * Invoked by the compiler to report diagnostics. If [uri] is null, so
  * is [begin] and [end]. No other arguments may be null. If [uri] is
  * not null, neither are [begin] and [end]. [uri] indicates the
  * compilation unit from where the diagnostic originates. [begin] and
  * [end] are zero-based character offsets from the beginning of the
  * compilaton unit. [message] is the diagnostic message, and [fatal]
  * indicates whether or not this diagnostic will prevent the compiler
  * from returning null.
  */
 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));
 }