(Fix #215) better error printing in editor & extension, adds mapping for editor

lib/src/messages.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 messages;
 
+import 'dart:json';
+
 import 'package:html5lib/dom_parsing.dart' show SourceSpan;
 import 'package:logging/logging.dart' show Level;
 
 import 'file_system/path.dart';
 import 'options.dart';
 import 'utils.dart';
 
 // TODO(jmesserly): remove the global messages. We instead use some
 // object that tracks compilation state.
 
@@ skipping 31 matching lines @@
     if (span == null) {
       if (file != null) output.add('$file: ');
       output.add(message);
     } else {
       output.add(span.toMessageString(
           file.toString(), message, useColors: colors));
     }
 
     return output.toString();
   }
+
+  String toJson() {
+    if (file == null) return toString();
+
+    var kind = (level == Level.SEVERE ? 'error' :
+        (level == Level.WARNING ? 'warning' : 'info'));
+    var json = {
+      'method': kind,
+      'params': {
+        'file': file.toString(),
+        'message': message,
+        'line': span == null ? 1 : span.line + 1,
+      }
+    };
+    if (span != null) {
+      json['params']['charStart'] = span.start;
+      json['params']['charEnd'] = span.end;
+    }
+    return JSON.stringify([json]);
+  }
 }
 
-typedef void PrintHandler(Object obj);
-
 /**
  * This class tracks and prints information, warnings, and errors emitted by the
  * compiler.
  */
 class Messages {
-  /** Called on every error. Set to blank function to supress printing. */
-  final PrintHandler printHandler;
-
   final CompilerOptions options;
+  final bool shouldPrint;
 
   final List<Message> messages = <Message>[];
 
-  Messages({CompilerOptions options, this.printHandler: print})
+  Messages({CompilerOptions options, this.shouldPrint: true})
       : options = options != null ? options : new CompilerOptions();
 
   // Convenience methods for testing
   int get length => messages.length;
   Message operator[](int index) => messages[index];
   void clear() {
     messages.clear();
   }
 
   /** [message] is considered a static compile-time error by the Dart lang. */
   void error(String message, SourceSpan span, {Path file}) {
     var msg = new Message(Level.SEVERE, message, file: file, span: span,
         useColors: options.useColors);
 
     messages.add(msg);
-
-    printHandler(msg);
+    if (shouldPrint) {

[Jennifer Messerly, 2012/12/06 19:59:54]

Put this in a helper function?
(since we had that bug once where the code paths got out of sync :) )

[Siggi Cherem (dart-lang), 2012/12/06 20:03:14]

Done.

+      print(options.jsonFormat ? msg.toJson() : msg);
+    }
   }
 
   /** [message] is considered a type warning by the Dart lang. */
   void warning(String message, SourceSpan span, {Path file}) {
     if (options.warningsAsErrors) {
       error(message, span, file: file);
     } else {
       var msg = new Message(Level.WARNING, message, file: file,
           span: span, useColors: options.useColors);
 
       messages.add(msg);
-
-      printHandler(msg);
+      if (shouldPrint) {
+        print(options.jsonFormat ? msg.toJson() : msg);
+      }
     }
   }
 
   /**
    * [message] at [file] will tell the user about what the compiler
    * is doing.
    */
   void info(String message, SourceSpan span, {Path file}) {
     var msg = new Message(Level.INFO, message, file: file, span: span,
         useColors: options.useColors);
 
     messages.add(msg);
+    if (shouldPrint && options.verbose) {
+      print(options.jsonFormat ? msg.toJson() : msg);
+    }
+  }
 
-    if (options.verbose) printHandler(msg);
-  }
 }