Add colors based on severity

lib/src/builder/build_step_impl.dart

@@ -102,10 +102,9 @@ class BuildStepImpl implements BuildStep {
       await _resolvers.get(toBarbackTransform(this), [toBarbackAssetId(id)]));
 
   /// Should be called after `build` has completed. This will wait until for
-  /// [_outputsCompleted] and will also close the [logger].
+  /// [_outputsCompleted].
   Future complete() async {
     await _outputsCompleted;
-    await _logger?.clearListeners();
   }
 
   /// Checks that [id] is a valid input, and throws an [InvalidInputException]

lib/src/generate/build_impl.dart

@@ -105,7 +105,7 @@ class BuildImpl {
               'one of its dependencies. This could be caused by a pub get or '
               'any other change. Please terminate the build script and restart '
               'it.';
-          _logger.warning(message);
+          _logger.severe(message);
           return new BuildResult(BuildStatus.Failure, buildType, [],
               exception: message);
         }
@@ -135,8 +135,10 @@ class BuildImpl {
           new Asset(_assetGraphId, JSON.encode(_assetGraph.serialize()));
       await _writer.writeAsString(assetGraphAsset);
 
+      _logger.info('Build succeeded');
       return result;
     } catch (e, s) {
+      _logger.severe('Build failed: $e\n\n$s');
       return new BuildResult(BuildStatus.Failure, buildType, [],
           exception: e, stackTrace: s);
     } finally {

lib/src/generate/options.dart

@@ -48,7 +48,23 @@ class BuildOptions {
     /// Set up logging
     logLevel ??= Level.INFO;
     Logger.root.level = logLevel;
-    onLog ??= stdout.writeln;
+    onLog ??= (LogRecord record) {
+      var color;
+      if (record.level < Level.WARNING) {
+        color = _cyan;
+      } else if (record.level < Level.SEVERE) {
+        color = _yellow;
+      } else {
+        color = _red;
+      }
+      var message = '$color[${record.level}]$_endColor ${record.loggerName}: '
+          '${record.message}\n';
+      if (record.level >= Level.SEVERE) {
+        stderr.write(message);
+      } else {
+        stdout.write(message);
+      }
+    };
     logListener = Logger.root.onRecord.listen(onLog);
 
     /// Set up other defaults.
@@ -67,3 +83,8 @@ class BuildOptions {
     directoryWatcherFactory ??= defaultDirectoryWatcherFactory;
   }
 }
+
+final _cyan = Platform.isWindows ? '' : '\u001b[36m';
+final _yellow = Platform.isWindows ? '' : '\u001b[33m';
+final _red = Platform.isWindows ? '' : '\u001b[31m';
+final _endColor = Platform.isWindows ? '' : '\u001b[0m';

lib/src/generate/watch_impl.dart

@@ -142,11 +142,6 @@ class WatchImpl {
       _currentBuild =
           _buildImpl.runBuild(validAsOf: validAsOf, updates: updatedInputsCopy);
       _currentBuild.then((result) {
-        if (result.status == BuildStatus.Success) {
-          _logger.info('Build completed successfully');
-        } else {
-          _logger.warning('Build failed');
-        }
         _resultStreamController.add(result);
         _currentBuild = null;
         if (_nextBuildScheduled) {
@@ -169,7 +164,7 @@ class WatchImpl {
       var watcher = _directoryWatcherFactory(package.location.toFilePath());
       watchers.add(watcher);
       _allListeners.add(watcher.events.listen((WatchEvent e) {
-        _logger.fine('Got WatchEvent for path ${e.path}');
+        _logger.finest('Got WatchEvent for path ${e.path}');
         var id = new AssetId(package.name, path.normalize(e.path));
         var node = _assetGraph.get(id);
         // Short circuit for deletes of nodes that aren't in the graph.

lib/src/server/server.dart

@@ -5,7 +5,6 @@ import 'dart:async';
 import 'dart:io';
 import 'package:shelf/shelf.dart';
 import 'package:shelf/shelf_io.dart';
-import 'package:shelf_static/shelf_static.dart';
 
 import '../generate/options.dart';
 import '../generate/watch_impl.dart';