(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() {
+    var kind = (level == Level.SEVERE ? 'error' :
+        (level == Level.WARNING ? 'warning' : 'info'));
+    var json = {
+      'method': kind,
+      'params': {
+        'file': file.toString(),
+        'line': span.line + 1,

[Jennifer Messerly, 2012/12/06 04:00:08]

Not all messages have a span. IIRC, info messages and failure to open a file do
not usually have it.

[Siggi Cherem (dart-lang), 2012/12/06 18:46:42]

good point - this made me realize that we have places where we don't even have a
file associated with the error (e.g. you provide bad path information on the
command line.)

Some of those errors can also be present if you have an incorrect build.dart, I
wonder if we should report those errors in the build.dart file location.

+        'message': message,
+        'charStart': span.start,
+        '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;

[Jennifer Messerly, 2012/12/06 04:00:08]

I think we should keep printHandler, so we can print messages as we go.

It would be fine to change the details though. i.e. it could be required, or it
could be an enum instead of a function (with 3 options -- don't print, print to
JSON, print normally).

Actually, could we derive this information from CompilerOptions? And if
CompilerOptions is not passed -- we're in silent mode (for tests)

-
   final CompilerOptions options;
 
   final List<Message> messages = <Message>[];
 
-  Messages({CompilerOptions options, this.printHandler: print})
+  Messages({CompilerOptions options})
       : 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);
   }
 
   /** [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);
     }
   }
 
   /**
    * [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 (options.verbose) printHandler(msg);
   }
 }