Add new features to package:async.

test/stream_completer_test.dart

+// Copyright (c) 2015, 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" show StreamCompleter;
+import "package:test/test.dart";
+
+main() {
+  test("a stream is linked before listening", () async {
+    var completer = new StreamCompleter();
+    completer.setSourceStream(createStream());
+    expect(completer.stream.toList(), completion([1, 2, 3, 4]));
+  });
+
+  test("listened to before a stream is linked", () async {
+    var completer = new StreamCompleter();
+    Future done = completer.stream.toList();

[nweiz, 2015/06/18 23:44:27]

Nit: "var"

[Lasse Reichstein Nielsen, 2015/06/30 10:34:14]

I have actually found full typing to catch bugs in my tests.
But ok :)

+    await flushMicrotasks();
+    completer.setSourceStream(createStream());
+    expect(done, completion([1, 2, 3, 4]));
+  });
+
+  test("cancel before linking a stream doesn't listen on stream", () async {
+    var completer = new StreamCompleter();
+    var subscription = completer.stream.listen(null);
+    subscription.pause();  // Should be ignored.
+    subscription.cancel();
+    completer.setSourceStream(new UnusableStream());  // Doesn't throw.
+  });
+
+  test("listen and pause before linking stream", () async {

[nweiz, 2015/06/18 23:44:27]

Also test that this pause triggers "onPause" in the source stream.

[Lasse Reichstein Nielsen, 2015/06/30 10:34:14]

Done.

+    var controller = new StreamCompleter();
+    var events = [];
+    var subscription = controller.stream.listen(events.add);
+    var done = subscription.asFuture();
+    subscription.pause();
+    controller.setSourceStream(createStream());
+    await flushMicrotasks();
+    expect(events, []);
+    subscription.resume();
+    await done;
+    expect(events, [1, 2, 3, 4]);
+  });
+
+  test("pause more than once", () async {
+    var completer = new StreamCompleter();
+    var events = [];
+    var subscription = completer.stream.listen(events.add);
+    Future done = subscription.asFuture();
+    subscription.pause();
+    subscription.pause();
+    subscription.pause();
+    completer.setSourceStream(createStream());
+    for (int i = 0; i < 3; i++) {
+      await flushMicrotasks();
+      expect(events, []);
+      subscription.resume();
+    }
+    await done;
+    expect(events, [1, 2, 3, 4]);
+  });
+
+  test("cancel new stream before source is done.", () async {
+    var completer = new StreamCompleter();
+    var listened = false;
+    var canceled = false;
+    var lastEvent = -1;
+    var controller = new StreamController(onListen: () { listened = true; },

[nweiz, 2015/06/18 23:44:27]

It's not actually in the style guide right now, but I asked Bob and Kathy and
the intention is that "() { ... }" isn't allowed (since there should always be a
newline after a statement). I think Kathy's going to update the style guide to
reflect that.

[Lasse Reichstein Nielsen, 2015/06/30 10:34:14]

That's silly.
I'll rewrite it to
   () => listened = true
which is being less precise (it suggests that the return value is significant)
just to get around the style guide.

So, mark me up as opposed to that ruling.

+                                          onCancel: () { canceled = true; });
+    var subscription;
+    subscription = completer.stream.listen(
+        (v) {

[nweiz, 2015/06/18 23:44:27]

"v" -> "value"

[Lasse Reichstein Nielsen, 2015/06/30 10:34:14]

Done.

+          expect(v, lessThan(3));
+          lastEvent = v;
+          if (v == 2) {
+            subscription.cancel();
+          }
+        },
+        onError: unreachable("error"),
+        onDone: unreachable("done"),
+        cancelOnError: true);
+    completer.setSourceStream(controller.stream);
+    expect(listened, isTrue);
+
+    await flushMicrotasks();
+    expect(canceled, isFalse);
+    controller.add(1);
+
+    await flushMicrotasks();
+    expect(lastEvent, 1);
+    expect(canceled, isFalse);
+    controller.add(2);
+
+    await flushMicrotasks();
+    expect(lastEvent, 2);
+    expect(canceled, isTrue);
+  });
+
+  test("complete with setEmpty before listening", () async {
+    var completer = new StreamCompleter();
+    completer.setEmpty();
+    var done = new Completer();
+    completer.stream.listen(
+        unreachable("data"),
+        onError: unreachable("error"),
+        onDone: done.complete);
+    await done.future;
+  });
+
+  test("complete with setEmpty after listening", () async {
+    var completer = new StreamCompleter();
+    var done = new Completer();
+    completer.stream.listen(
+        unreachable("data"),
+        onError: unreachable("error"),
+        onDone: done.complete);
+    completer.setEmpty();
+    await done.future;
+  });
+
+  test("source stream isn't listened to until completer stream is.", () async {

[nweiz, 2015/06/18 23:44:27]

Nit: no period

[Lasse Reichstein Nielsen, 2015/06/30 10:34:14]

Done.

+    var completer = new StreamCompleter();
+    bool listened = false;

[nweiz, 2015/06/18 23:44:27]

Nit: "var"

[Lasse Reichstein Nielsen, 2015/06/30 10:34:14]

Done.

+    var controller;
+    controller = new StreamController(onListen: () {
+      listened = true;
+      () async { controller.close(); } ();  // In later microtask.

[nweiz, 2015/06/18 23:44:27]

I think "scheduleMicrotask" is a little more explicit here.

[Lasse Reichstein Nielsen, 2015/06/30 10:34:14]

And it has exactly the same length. Scary.

+    });
+
+    completer.setSourceStream(controller.stream);
+    await flushMicrotasks();
+    expect(listened, isFalse);
+    var subscription = completer.stream.listen(null);
+    expect(listened, isTrue);
+    await subscription.asFuture();
+  });
+
+  test("cancelOnError true when listening before linking stream", () async {
+    var completer = new StreamCompleter();
+    var listened = false;
+    var canceled = false;
+    var lastEvent = -1;
+    var controller = new StreamController(onListen: () { listened = true; },
+                                          onCancel: () { canceled = true; });
+    var subscription = completer.stream.listen(
+        (v) {
+          expect(v, lessThan(3));
+          lastEvent = v;
+        },
+        onError: (v) {
+          expect(v, "3");
+          lastEvent = v;
+        },
+        onDone: unreachable("done"),
+        cancelOnError: true);
+    completer.setSourceStream(controller.stream);
+    expect(listened, isTrue);
+
+    await flushMicrotasks();
+    expect(canceled, isFalse);
+    controller.add(1);
+
+    await flushMicrotasks();
+    expect(lastEvent, 1);
+    expect(canceled, isFalse);
+    controller.add(2);
+
+    await flushMicrotasks();
+    expect(lastEvent, 2);
+    expect(canceled, isFalse);
+    controller.addError("3");
+
+    await flushMicrotasks();
+    expect(lastEvent, "3");
+    expect(canceled, isTrue);
+  });
+
+  test("cancelOnError true when listening after linking stream", () async {
+    var completer = new StreamCompleter();
+    var listened = false;
+    var canceled = false;
+    var lastEvent = -1;
+    var controller = new StreamController(onListen: () { listened = true; },
+                                          onCancel: () { canceled = true; });
+    completer.setSourceStream(controller.stream);
+    controller.add(1);
+    expect(listened, isFalse);
+
+    var subscription = completer.stream.listen(
+        (v) {
+          expect(v, lessThan(3));
+          lastEvent = v;
+        },
+        onError: (v) {
+          expect(v, "3");
+          lastEvent = v;
+        },
+        onDone: unreachable("done"),
+        cancelOnError: true);
+
+    expect(listened, isTrue);
+
+    await flushMicrotasks();
+    expect(lastEvent, 1);
+    expect(canceled, isFalse);
+    controller.add(2);
+
+    await flushMicrotasks();
+    expect(lastEvent, 2);
+    expect(canceled, isFalse);
+    controller.addError("3");
+
+    await flushMicrotasks();
+    expect(canceled, isTrue);
+  });
+
+  test("linking a stream after setSourceStream before listen", () async {
+    var completer = new StreamCompleter();
+    completer.setSourceStream(createStream());
+    expect(() { completer.setSourceStream(createStream()); }, throws);
+    expect(() { completer.setEmpty(createStream()); }, throws);
+    await completer.stream.toList();
+    // Still fails after source is done
+    expect(() { completer.setSourceStream(createStream()); }, throws);
+    expect(() { completer.setEmpty(createStream()); }, throws);
+  });
+
+  test("linking a stream after setSourceStream after listen", () async {
+    var completer = new StreamCompleter();
+    var list = completer.stream.toList();
+    completer.setSourceStream(createStream());
+    expect(() { completer.setSourceStream(createStream()); }, throws);
+    expect(() { completer.setEmpty(createStream()); }, throws);
+    await list;
+    // Still fails after source is done.
+    expect(() { completer.setSourceStream(createStream()); }, throws);
+    expect(() { completer.setEmpty(createStream()); }, throws);
+  });
+
+  test("linking a stream after setEmpty before listen", () async {
+    var completer = new StreamCompleter();
+    completer.setEmpty();
+    expect(() { completer.setSourceStream(createStream()); }, throws);
+    expect(() { completer.setEmpty(createStream()); }, throws);
+    await completer.stream.toList();
+    // Still fails after source is done
+    expect(() { completer.setSourceStream(createStream()); }, throws);
+    expect(() { completer.setEmpty(createStream()); }, throws);
+  });
+
+  test("linking a stream after setEmpty() after listen", () async {
+    var completer = new StreamCompleter();
+    var list = completer.stream.toList();
+    completer.setEmpty();
+    expect(() { completer.setSourceStream(createStream()); }, throws);
+    expect(() { completer.setEmpty(createStream()); }, throws);
+    await list;
+    // Still fails after source is done.
+    expect(() { completer.setSourceStream(createStream()); }, throws);
+    expect(() { completer.setEmpty(createStream()); }, throws);
+  });
+
+  test("Listening more than once after setting stream", () async {

[nweiz, 2015/06/18 23:44:27]

Nit: "listening" (also below)

[Lasse Reichstein Nielsen, 2015/06/30 10:34:14]

Done.

+    var completer = new StreamCompleter();
+    completer.setSourceStream(createStream());
+    var list = completer.stream.toList();
+    expect(() { completer.stream.toList(); }, throws);
+    await list;
+    expect(() { completer.stream.toList(); }, throws);
+  });
+
+  test("Listening more than once before setting stream", () async {
+    var completer = new StreamCompleter();
+    var list = completer.stream.toList();
+    expect(() { completer.stream.toList(); }, throws);
+  });
+
+  test("setting onData etc. before and after setting stream", () async {
+    var completer = new StreamCompleter();
+    var controller = new StreamController();
+    var subscription = completer.stream.listen(null);
+    var lastEvent = 0;
+    subscription.onData((v) { lastEvent = v; });
+    subscription.onError((v) { lastEvent = "$v"; });
+    subscription.onDone(() { lastEvent = -1; });
+    completer.setSourceStream(controller.stream);
+    await flushMicrotasks();
+    controller.add(1);
+    await flushMicrotasks();
+    expect(lastEvent, 1);
+    controller.addError(2);
+    await flushMicrotasks();
+    expect(lastEvent, "2");
+    subscription.onData((v) { lastEvent = -v; });
+    subscription.onError((v) { lastEvent = "${-v}"; });
+    controller.add(1);
+    await flushMicrotasks();
+    expect(lastEvent, -1);
+    controller.addError(2);
+    await flushMicrotasks();
+    expect(lastEvent, "-2");
+    controller.close();
+    await flushMicrotasks();
+    expect(lastEvent, -1);
+  });
+
+  test("pause w/ resume future accross setting stream", () async {
+    var completer = new StreamCompleter();
+    var resume = new Completer();
+    var subscription = completer.stream.listen(unreachable("data"));
+    var lastEvent = 0;
+    subscription.pause(resume.future);
+    await flushMicrotasks();
+    completer.setSourceStream(createStream());
+    await flushMicrotasks();
+    resume.complete();
+    var events = [];
+    subscription.onData(events.add);
+    await subscription.asFuture();
+    expect(events, [1, 2, 3, 4]);
+  });
+
+  test("asFuture with error accross setting stream", () async {
+    var completer = new StreamCompleter();
+    var controller = new StreamController();
+    var subscription = completer.stream.listen(unreachable("data"),
+                                               cancelOnError: false);
+    var done = subscription.asFuture();
+    expect(controller.hasListener, isFalse);
+    completer.setSourceStream(controller.stream);
+    await flushMicrotasks();
+    expect(controller.hasListener, isTrue);
+    controller.addError(42);
+    await done.then(unreachable("data"), onError: (error) {
+      expect(error, 42);
+    });
+    expect(controller.hasListener, isFalse);
+  });
+}
+
+/// A zero-millisecond timer should wait until after all microtasks.
+Future flushMicrotasks() => new Future.delayed(Duration.ZERO);

[nweiz, 2015/06/18 23:44:27]

Consider moving this (and maybe [unreachable] and [UnusuableStream] as well)
into a test/utils.dart file.

[Lasse Reichstein Nielsen, 2015/06/30 10:34:14]

Done.

+
+Stream<int> createStream() async* {
+  yield 1;
+  await flushMicrotasks();
+  yield 2;
+  await flushMicrotasks();
+  yield 3;
+  await flushMicrotasks();
+  yield 4;
+}
+
+unreachable(String name) => ([a, b]) { fail("Unreachable: $name"); };
+
+class UnusableStream extends Stream {
+  listen(onData, {onError, onDone, cancelOnError}) {
+    throw new UnimplementedError("Gotcha!");
+  }
+}