Use ansi color in the dartanalyzer cli output.

pkg/analyzer_cli/lib/src/ansi.dart

+// Copyright (c) 2017, 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.
+
+import 'dart:io';
+
+/// Public for testing.
+bool runningTests = false;
+
+bool terminalSupportsAnsi() {
+  return !runningTests &&
+      !Platform.isWindows &&

[karlklose, 2017/03/24 09:08:08]

Here is the detection code we use in fasta, which also works on (recent builds
of) Windows 10:
https://github.com/dart-lang/sdk/blob/master/pkg/front_end/lib/src/fasta/colo...

[devoncarew, 2017/03/25 22:33:17]

Thanks! Looks comprehensive. I know package:test and flutter have their own
detection code as well. We should likely unify where possible.

+      stdioType(stdout) == StdioType.TERMINAL;
+}
+
+class AnsiLogger {

[Brian Wilkerson, 2017/03/23 17:09:51]

Seems like this would be useful across multiple tools. There are two packages on
pub that provide some level of support:
- https://pub.dartlang.org/packages/ansicolor
- https://pub.dartlang.org/packages/console
Should we be using one of them?

[devoncarew, 2017/03/25 22:33:17]

Perhaps? I do like how lightweight our impl is, and that it doesn't introduce
dependencies. Would prefer to keep this minimal impl for now.

+  final bool useAnsi;
+
+  String get cyan => _code('\u001b[36m');
+  String get green => _code('\u001b[32m');
+  String get magenta => _code('\u001b[35m');
+  String get red => _code('\u001b[31m');
+  String get yellow => _code('\u001b[33m');
+  String get blue => _code('\u001b[34m');
+  String get gray => _code('\u001b[1;30m');
+  String get none => _code('\u001b[0m');
+  String get noColor => _code('\u001b[39m');
+  String get bold => _code('\u001b[1m');
+
+  AnsiLogger(this.useAnsi);
+
+  String get bullet => (runningTests || !Platform.isWindows) ? '•' : '-';
+
+  String _code(String ansiCode) => useAnsi ? ansiCode : '';
+}