Add a StreamSinkCompleter class.

test/stream_sink_completer_test.dart

+// Copyright (c) 2016, 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:async";
+
+import "package:async/async.dart";
+import "package:test/test.dart";
+
+import "utils.dart";
+
+main() {
+  var completer;
+  setUp(() {
+    completer = new StreamSinkCompleter();
+  });
+
+  group("when a stream is linked before events are added", () {
+    test("data events are forwarded", () {
+      var sink = new TestSink();
+      completer.setDestinationSink(sink);
+      completer.sink..add(1)..add(2)..add(3)..add(4);
+
+      expect(sink.results[0].asValue.value, equals(1));
+      expect(sink.results[1].asValue.value, equals(2));
+      expect(sink.results[2].asValue.value, equals(3));
+      expect(sink.results[3].asValue.value, equals(4));
+    });
+
+    test("error events are forwarded", () {
+      var sink = new TestSink();
+      completer.setDestinationSink(sink);
+      completer.sink..addError("oh no")..addError("that's bad");
+
+      expect(sink.results[0].asError.error, equals("oh no"));
+      expect(sink.results[1].asError.error, equals("that's bad"));
+    });
+
+    test("addStream is forwarded", () async {
+      var sink = new TestSink();
+      completer.setDestinationSink(sink);
+
+      var controller = new StreamController();
+      completer.sink.addStream(controller.stream);
+
+      controller.add(1);
+      controller.addError("oh no");
+      controller.add(2);
+      controller.addError("that's bad");
+      await flushMicrotasks();
+
+      expect(sink.results[0].asValue.value, equals(1));
+      expect(sink.results[1].asError.error, equals("oh no"));
+      expect(sink.results[2].asValue.value, equals(2));
+      expect(sink.results[3].asError.error, equals("that's bad"));
+      expect(sink.isClosed, isFalse);
+
+      controller.close();
+      await flushMicrotasks();
+      expect(sink.isClosed, isFalse);
+    });
+
+    test("close() is forwarded", () {
+      var sink = new TestSink();
+      completer.setDestinationSink(sink);
+      completer.sink.close();
+      expect(sink.isClosed, isTrue);
+    });
+
+    test("the future from the inner close() is returned", () async {
+      var closeCompleter = new Completer();
+      var sink = new TestSink(onDone: () => closeCompleter.future);
+      completer.setDestinationSink(sink);
+
+      var closeCompleted = false;
+      completer.sink.close().then(expectAsync((_) {
+        closeCompleted = true;
+      }));
+
+      await flushMicrotasks();
+      expect(closeCompleted, isFalse);
+
+      closeCompleter.complete();
+      await flushMicrotasks();
+      expect(closeCompleted, isTrue);
+    });
+
+    test("errors are forwarded from the inner close()", () {
+      var sink = new TestSink(onDone: () => throw "oh no");
+      completer.setDestinationSink(sink);
+      expect(completer.sink.done, throwsA("oh no"));
+      expect(completer.sink.close(), throwsA("oh no"));
+    });
+
+    test("errors aren't top-leveled if only close() is listened to", () async {
+      var sink = new TestSink(onDone: () => throw "oh no");
+      completer.setDestinationSink(sink);
+      expect(completer.sink.close(), throwsA("oh no"));
+
+      // Give the event loop a chance to top-level errors if it's going to.
+      await flushMicrotasks();

[Lasse Reichstein Nielsen, 2016/01/21 07:28:47]

I'd wait for a timer event here, to be sure all microtasks are done.
await new Future((){}); should do it, but you can probably give it a more
readable name.

[nweiz, 2016/01/21 20:59:05]

That's exactly what flushMicrotasks() does, actually :).

+    });
+
+    test("errors aren't top-leveled if only done is listened to", () async {
+      var sink = new TestSink(onDone: () => throw "oh no");
+      completer.setDestinationSink(sink);
+      completer.sink.close();
+      expect(completer.sink.done, throwsA("oh no"));
+
+      // Give the event loop a chance to top-level errors if it's going to.
+      await flushMicrotasks();
+    });
+  });
+
+  group("when a stream is linked after events are added", () {
+    test("data events are forwarded", () async {
+      completer.sink..add(1)..add(2)..add(3)..add(4);
+      await flushMicrotasks();
+
+      var sink = new TestSink();
+      completer.setDestinationSink(sink);
+      await flushMicrotasks();
+
+      expect(sink.results[0].asValue.value, equals(1));
+      expect(sink.results[1].asValue.value, equals(2));
+      expect(sink.results[2].asValue.value, equals(3));
+      expect(sink.results[3].asValue.value, equals(4));
+    });
+
+    test("error events are forwarded", () async {
+      completer.sink..addError("oh no")..addError("that's bad");
+      await flushMicrotasks();
+
+      var sink = new TestSink();
+      completer.setDestinationSink(sink);
+      await flushMicrotasks();
+
+      expect(sink.results[0].asError.error, equals("oh no"));
+      expect(sink.results[1].asError.error, equals("that's bad"));
+    });
+
+    test("addStream is forwarded", () async {
+      var controller = new StreamController();
+      completer.sink.addStream(controller.stream);
+
+      controller.add(1);
+      controller.addError("oh no");
+      controller.add(2);
+      controller.addError("that's bad");
+      controller.close();
+      await flushMicrotasks();
+
+      var sink = new TestSink();
+      completer.setDestinationSink(sink);
+      await flushMicrotasks();
+
+      expect(sink.results[0].asValue.value, equals(1));
+      expect(sink.results[1].asError.error, equals("oh no"));
+      expect(sink.results[2].asValue.value, equals(2));
+      expect(sink.results[3].asError.error, equals("that's bad"));
+      expect(sink.isClosed, isFalse);
+    });
+
+    test("close() is forwarded", () async {
+      completer.sink.close();
+      await flushMicrotasks();
+
+      var sink = new TestSink();
+      completer.setDestinationSink(sink);
+      await flushMicrotasks();
+
+      expect(sink.isClosed, isTrue);
+    });
+
+    test("the future from the inner close() is returned", () async {
+      var closeCompleted = false;
+      completer.sink.close().then(expectAsync((_) {
+        closeCompleted = true;
+      }));
+      await flushMicrotasks();
+
+      var closeCompleter = new Completer();
+      var sink = new TestSink(onDone: () => closeCompleter.future);
+      completer.setDestinationSink(sink);
+      await flushMicrotasks();
+      expect(closeCompleted, isFalse);
+
+      closeCompleter.complete();
+      await flushMicrotasks();
+      expect(closeCompleted, isTrue);
+    });
+
+    test("errors are forwarded from the inner close()", () async {
+      expect(completer.sink.done, throwsA("oh no"));
+      expect(completer.sink.close(), throwsA("oh no"));
+      await flushMicrotasks();
+
+      var sink = new TestSink(onDone: () => throw "oh no");
+      completer.setDestinationSink(sink);
+    });
+
+    test("errors aren't top-leveled if only close() is listened to", () async {
+      expect(completer.sink.close(), throwsA("oh no"));
+      await flushMicrotasks();
+
+      var sink = new TestSink(onDone: () => throw "oh no");
+      completer.setDestinationSink(sink);
+
+      // Give the event loop a chance to top-level errors if it's going to.
+      await flushMicrotasks();
+    });
+
+    test("errors aren't top-leveled if only done is listened to", () async {
+      completer.sink.close();
+      expect(completer.sink.done, throwsA("oh no"));
+      await flushMicrotasks();
+
+      var sink = new TestSink(onDone: () => throw "oh no");
+      completer.setDestinationSink(sink);
+
+      // Give the event loop a chance to top-level errors if it's going to.
+      await flushMicrotasks();
+    });
+  });
+
+  test("doesn't allow the destination sink to be set multiple times", () {
+    completer.setDestinationSink(new TestSink());
+    expect(() => completer.setDestinationSink(new TestSink()),
+        throwsStateError);
+    expect(() => completer.setDestinationSink(new TestSink()),
+        throwsStateError);
+  });

[Lasse Reichstein Nielsen, 2016/01/21 07:28:47]

Could you make more tests with the "done" getter:
- Cover all six orderings of add event, read done, setDestinationSink
- make the sink's onDone return something recognizable, so yo can see that the
onDone gets the correct result in all cases.

[nweiz, 2016/01/21 20:59:05]

Done. Four of these were already being tested, so I added explicit tests for the
last two.
I don't like checking the value, because the "done" future really shouldn't have
a value anyway (it would be a Future<void> if we had a way of representing
that). But I do check that it blocks as long as the returned future does, and I
check that any internal errors thrown are piped correctly.

+}