First shot at source maps generation in dart2js.

lib/compiler/implementation/dart2js.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('dart2js');
 
 #import('dart:io');
 #import('dart:uri');
 #import('dart:utf');
 
@@ skipping 53 matching lines @@
   }
 }
 
 void compile(List<String> argv) {
   Uri cwd = getCurrentDirectory();
   bool throwOnError = false;
   bool showWarnings = true;
   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;
   bool wantHelp = false;
 
   passThrough(String argument) => options.add(argument);
 
   setLibraryRoot(String argument) {
     libraryRoot = cwd.resolve(extractPath(argument));
   }
 
   setPackageRoot(String argument) {
     packageRoot = cwd.resolve(extractPath(argument));
   }
 
   setOutput(String argument) {
     explicitOut = true;
     out = cwd.resolve(nativeToUriPath(extractParameter(argument)));
   }
 
+  setSourceMapOutput(String argument) {
+    sourceMapOut = cwd.resolve(nativeToUriPath(extractParameter(argument)));
+  }
+
   handleShortOptions(String argument) {
     var shortOptions = argument.substring(1).splitChars();
     for (var shortOption in shortOptions) {
       switch (shortOption) {
         case 'v':
           verbose = true;
           break;
         case 'h':
         case '?':
           wantHelp = true;
           break;
         case 'c':
           passThrough('--enable-checked-mode');
           break;
         default:
           throw 'Internal error: "$shortOption" did not match';
       }
     }
   }
 
   List<String> arguments = <String>[];
   List<OptionHandler> handlers = <OptionHandler>[
     new OptionHandler('-[chv?]+', handleShortOptions),
     new OptionHandler('--throw-on-error', (_) => throwOnError = true),
     new OptionHandler('--suppress-warnings', (_) => showWarnings = false),
     new OptionHandler('--output-type=dart|--output-type=js', passThrough),
     new OptionHandler('--verbose', (_) => verbose = true),
     new OptionHandler('--library-root=.+', setLibraryRoot),
     new OptionHandler('--out=.+|-o.+', setOutput),
+    new OptionHandler('--source-map-out=.+', setSourceMapOutput),
     new OptionHandler('--allow-mock-compilation', passThrough),
     new OptionHandler('--unparse-validation', passThrough),
     new OptionHandler('--no-colors', (_) => colors.enabled = false),

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

I think you accidentally copied a line here.

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

Done.

+    new OptionHandler('--no-colors', (_) => colors.enabled = false),
     new OptionHandler('--enable[_-]checked[_-]mode|--checked',
                       (_) => passThrough('--enable-checked-mode')),
     new OptionHandler(@'--help|/\?|/h', (_) => wantHelp = true),
     new OptionHandler(@'--package-root=.+|-p.+', setPackageRoot),
     // The following two options must come last.
     new OptionHandler('-.*', (String argument) {
       helpAndFail('Error: Unknown option "$argument".');
     }),
     new OptionHandler('.*', (String argument) {
       arguments.add(nativeToUriPath(argument));
@@ skipping 30 matching lines @@
       new SourceFile(relativize(cwd, uri), source);
     return new Future.immediate(source);
   }
 
   void info(var message) {
     if (verbose) print('${colors.green("info:")} $message');
   }
 
   bool isAborting = false;
 
   void handler(Uri uri, int begin, int end, String message, bool fatal) {

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

Earlier today, I created changed "fatal" to kind.

How about we hack in sources maps using this approach:

if (kind.name == 'source map') {
  // store source map.
  return;
}

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

Done.

     if (isAborting) return;
     if (uri === null && !fatal) {
       info(message);
       return;
     }
     if (uri === null) {
       assert(fatal);
       print(message);
     } else if (fatal || showWarnings) {
       SourceFile file = sourceFiles[uri.toString()];
       print(file.getLocationMessage(message, begin, end, true));
     }
     if (fatal && throwOnError) {
       isAborting = true;
       throw new AbortLeg(message);
     }
   }
 
   Uri uri = cwd.resolve(arguments[0]);
   if (packageRoot === null) {
     packageRoot = uri.resolve('./packages/');
   }
 
   info('compiling $uri');
   info('package root is $packageRoot');
 
   // 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;
+  api.CompiledScript script = api.compile(
+      uri, libraryRoot, packageRoot, provider, handler, options).value;
+  String code = script.code;
   if (code === null) {
     fail('Error: Compilation failed.');
   }
+  if (sourceMapOut !== null) {
+    writeString(sourceMapOut, script.sourceMap);
+    code = '$code\n//@ sourceMappingURL=$sourceMapOut';
+  }
   writeString(out, code);
   int jsBytesWritten = code.length;
   info('compiled $dartBytesRead bytes Dart -> $jsBytesWritten bytes JS '
        'in ${relativize(cwd, out)}');
   if (!explicitOut) {
     String input = uriPathToNative(arguments[0]);
     String output = relativize(cwd, out);
     print('Dart file $input compiled to JavaScript: $output');
   }
 }
@@ skipping 118 matching lines @@
     } catch (var ignored) {
       print('Internal error: error while printing exception');
     }
     try {
       print(trace);
     } finally {
       exit(253); // 253 is recognized as a crash by our test scripts.
     }
   }
 }