Add StreamOutput

Author: haarts

lib/logger.dart

@@ -6,6 +6,7 @@ export 'src/ansi_color.dart';
 export 'src/filters/debug_filter.dart';
 export 'src/filters/production_filter.dart';
 export 'src/outputs/console_output.dart';
+export 'src/outputs/stream_output.dart';
 export 'src/outputs/memory_output.dart';
 export 'src/printers/pretty_printer.dart';
 export 'src/printers/simple_printer.dart';

lib/src/outputs/stream_output.dart

@@ -0,0 +1,34 @@
+import 'dart:async';
+
+import 'package:logger/src/logger.dart';
+import 'package:logger/src/log_output.dart';
+
+class StreamOutput extends LogOutput {
+  StreamController<List<String>> _controller;
+  bool _shouldForward = false;
+
+  StreamOutput() {
+    _controller = StreamController<List<String>>(
+      onListen: () => _shouldForward = true,
+      onPause: () => _shouldForward = false,
+      onResume: () => _shouldForward = true,
+      onCancel: () => _shouldForward = false,
+    );
+  }
+
+  Stream<List<String>> get stream => _controller.stream;
+
+  @override
+  void output(OutputEvent event) {
+    if (!_shouldForward) {
+      return;
+    }
+
+    _controller.add(event.lines);
+  }
+
+  @override
+  void destroy() {
+    _controller.close();
+  }
+}

test/outputs/stream_output_test.dart

@@ -0,0 +1,39 @@
+import 'package:test/test.dart';
+import 'package:logger/logger.dart';
+
+void main() {
+  test('writes to a Stream', () {
+    var out = StreamOutput();
+
+    out.stream.listen((var e) {
+      expect(e, ['hi there']);
+    });
+
+    out.output(OutputEvent(Level.debug, ['hi there']));
+  });
+
+  test('respects listen', () {
+    var out = StreamOutput();
+
+    out.output(OutputEvent(Level.debug, ['dropped']));
+
+    out.stream.listen((var e) {
+      expect(e, ['hi there']);
+    });
+
+    out.output(OutputEvent(Level.debug, ['hi there']));
+  });
+
+  test('respects pause', () {
+    var out = StreamOutput();
+
+    var sub = out.stream.listen((var e) {
+      expect(e, ['hi there']);
+    });
+
+    sub.pause();
+    out.output(OutputEvent(Level.debug, ['dropped']));
+    sub.resume();
+    out.output(OutputEvent(Level.debug, ['hi there']));
+  });
+}