Add linter by default for polymer's pub-build, also cleans up the linter code.

pkg/polymer/lib/src/build/runner.dart

 // Copyright (c) 2013, 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.
 
 /**
  * Definitions used to run the polymer linter and deploy tools without using
  * pub serve or pub deploy.
  */
 library polymer.src.build.runner;
 
@@ skipping 24 matching lines @@
 
   /** Whether to run transformers on the test folder. */
   final bool transformTests;
 
   /** Whether to apply transformers on polymer dependencies. */
   final bool transformPolymerDependencies;
 
   /** Directory where to generate code, if any. */
   final String outDir;
 
+  /**
+   * Whether to print error messages using a json-format that tools, such as the
+   * Dart Editor, can process.
+   */
+  final String machineFormat;
+
   BarbackOptions(this.phases, this.outDir, {currentPackage, packageDirs,
-      this.transformTests: false, this.transformPolymerDependencies: false})
+      this.transformTests: false, this.transformPolymerDependencies: false,
+      this.machineFormat: false})
       : currentPackage = (currentPackage != null
           ? currentPackage : readCurrentPackageFromPubspec()),
         packageDirs = (packageDirs != null
           ? packageDirs : _readPackageDirsFromPub(currentPackage));
 
 }
 
 /**
  * Creates a barback system as specified by [options] and runs it.  Returns a
  * future that contains the list of assets generated after barback runs to
  * completion.
  */
 Future<AssetSet> runBarback(BarbackOptions options) {
   var barback = new Barback(new _PolymerPackageProvider(options.packageDirs));
   _initBarback(barback, options);
-  _attachListeners(barback);
+  _attachListeners(barback, options);
   if (options.outDir == null) return barback.getAllAssets();
   return _emitAllFiles(barback, options);
 }
 
 /** Extract the current package from the pubspec.yaml file. */
 String readCurrentPackageFromPubspec([String dir]) {
   var pubspec = new File(
       dir == null ? 'pubspec.yaml' : path.join(dir, 'pubspec.yaml'));
   if (!pubspec.existsSync()) {
     print('error: pubspec.yaml file not found, please run this script from '
@@ skipping 91 matching lines @@
   }
 
   // In case of the current package, include also 'web'.
   addAssets(options.currentPackage, 'web');
   if (options.transformTests) addAssets(options.currentPackage, 'test');
 
   barback.updateSources(assets);
 }
 
 /** Attach error listeners on [barback] so we can report errors. */
-void _attachListeners(Barback barback) {
+void _attachListeners(Barback barback, BarbackOptions options) {
   // Listen for errors and results
   barback.errors.listen((e) {
     var trace = null;
     if (e is Error) trace = e.stackTrace;
     if (trace != null) {
       print(Trace.format(trace));
     }
     print('error running barback: $e');
     exit(1);
   });
 
   barback.results.listen((result) {
     if (!result.succeeded) {
       print("build failed with errors: ${result.errors}");
       exit(1);
     }
   });
+
+  barback.log.listen((entry) {
+    if (options.machineFormat) {
+      print(_jsonFormatter(entry));
+    } else {
+      print(_consoleFormatter(entry));
+    }
+  });
 }
 
 /**
  * Emits all outputs of [barback] and copies files that we didn't process (like
  * polymer's libraries).
  */
 Future _emitAllFiles(Barback barback, BarbackOptions options) {
   return barback.getAllAssets().then((assets) {
     // Delete existing output folder before we generate anything
     var dir = new Directory(options.outDir);
@@ skipping 102 matching lines @@
 Future _copyFile(String inpath, String outpath) {
   _ensureDir(path.dirname(outpath));
   return new File(inpath).openRead().pipe(new File(outpath).openWrite());
 }
 
 /** Write contents of an [asset] into a file at [filepath]. */
 Future _writeAsset(String filepath, Asset asset) {
   _ensureDir(path.dirname(filepath));
   return asset.read().pipe(new File(filepath).openWrite());
 }
+
+String _kindFromEntry(LogEntry entry) {
+  var level = entry.level;
+  return level == LogLevel.ERROR ? 'error'
+      : (level == LogLevel.WARNING ? 'warning' : 'info');
+}
+
+/**
+ * Formatter that generates messages using a format that can be parsed
+ * by tools, such as the Dart Editor, for reporting error messages.
+ */
+String _jsonFormatter(LogEntry entry) {
+  var kind = _kindFromEntry(entry);
+  var span = entry.span;
+  return JSON.encode((span == null)
+      ? [{'method': kind, 'params': {'message': entry.message}}]
+      : [{'method': kind,
+          'params': {
+            'file': span.sourceUrl,
+            'message': entry.message,
+            'line': span.start.line + 1,
+            'charStart': span.start.offset,
+            'charEnd': span.end.offset,
+          }}]);
+}
+
+/**
+ * Formatter that generates messages that are easy to read on the console (used
+ * by default).
+ */
+String _consoleFormatter(LogEntry entry) {
+  var kind = _kindFromEntry(entry);
+  var useColors = stdioType(stdout) == StdioType.TERMINAL;
+  var levelColor = (kind == 'error') ? _RED_COLOR : _MAGENTA_COLOR;
+  var output = new StringBuffer();
+  if (useColors) output.write(levelColor);
+  output..write(kind)..write(' ');
+  if (useColors) output.write(_NO_COLOR);
+  if (entry.span == null) {
+    output.write(entry.message);
+  } else {
+    output.write(entry.span.getLocationMessage(entry.message,
+          useColors: useColors,
+          color: levelColor));
+  }
+  return output.toString();
+}
+
+const String _RED_COLOR = '\u001b[31m';
+const String _MAGENTA_COLOR = '\u001b[35m';
+const String _NO_COLOR = '\u001b[0m';