Add a StreamSinkTransformer class.

test/stream_sink_transformer_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 filevents.
+
+import "dart:async";
+
+import "package:async/async.dart";
+import "package:test/test.dart";
+
+import "utils.dart";
+
+void main() {
+  var controller;
+  setUp(() {
+    controller = new StreamController();
+  });
+
+  group("fromStreamTransformer", () {
+    test("transforms data events", () {
+      var transformer = new StreamSinkTransformer.fromStreamTransformer(
+          new StreamTransformer.fromHandlers(handleData: (i, sink) {
+            sink.add(i * 2);
+          }));
+      var sink = transformer.bind(controller.sink);
+
+      var results = [];
+      controller.stream.listen(results.add, onDone: expectAsync(() {
+        expect(results, equals([2, 4, 6]));
+      }));
+
+      sink.add(1);
+      sink.add(2);
+      sink.add(3);
+      sink.close();
+    });
+
+    test("transforms error events", () {
+      var transformer = new StreamSinkTransformer.fromStreamTransformer(
+          new StreamTransformer.fromHandlers(
+              handleError: (i, stackTrace, sink) {
+                sink.addError(i * 2, stackTrace);
+              }));
+      var sink = transformer.bind(controller.sink);
+
+      var results = [];
+      controller.stream.listen(expectAsync((_) {}, count: 0),
+          onError: (error, stackTrace) {
+            results.add(error);
+          },
+          onDone: expectAsync(() {
+            expect(results, equals([2, 4, 6]));
+          }));
+
+      sink.addError(1);
+      sink.addError(2);
+      sink.addError(3);
+      sink.close();
+    });
+
+    test("transforms done events", () {
+      var transformer = new StreamSinkTransformer.fromStreamTransformer(
+          new StreamTransformer.fromHandlers(
+              handleDone: (sink) {
+                sink.add(1);
+                sink.close();
+              }));
+      var sink = transformer.bind(controller.sink);
+
+      var results = [];
+      controller.stream.listen(results.add, onDone: expectAsync(() {
+        expect(results, equals([1]));
+      }));
+
+      sink.close();
+    });
+
+    test("forwards the future from inner.close", () async {
+      var transformer = new StreamSinkTransformer.fromStreamTransformer(
+          new StreamTransformer.fromHandlers());
+      var innerSink = new CompleterStreamSink();
+      var sink = transformer.bind(innerSink);
+
+      // The futures shouldn't complete until the inner sink's close future
+      // completes.
+      var doneResult = new ResultFuture(sink.done);
+      doneResult.catchError((_) {});
+      var closeResult = new ResultFuture(sink.close());
+      closeResult.catchError((_) {});
+      await flushMicrotasks();
+      expect(doneResult.isComplete, isFalse);
+      expect(closeResult.isComplete, isFalse);
+
+      // Once the inner sink is completed, the futures should fire. 
+      innerSink.completer.complete();
+      await flushMicrotasks();
+      expect(doneResult.isComplete, isTrue);
+      expect(closeResult.isComplete, isTrue);
+    });
+
+    test("doesn't top-level the future from inner.close", () async {
+      var transformer = new StreamSinkTransformer.fromStreamTransformer(
+          new StreamTransformer.fromHandlers(handleData: (_, sink) {
+            sink.close();
+          }));
+      var innerSink = new CompleterStreamSink();
+      var sink = transformer.bind(innerSink);
+
+      // This will close the inner sink, but it shouldn't top-level the error.
+      sink.add(1);
+      innerSink.completer.completeError("oh no");
+      await flushMicrotasks();
+
+      // The error should be piped through done and close even if they're called
+      // after the underlying sink is closed.
+      expect(sink.done, throwsA("oh no"));
+      expect(sink.close(), throwsA("oh no"));
+    });
+  });
+
+  group("fromHandlers", () {
+    test("transforms data events", () {
+      var transformer = new StreamSinkTransformer.fromHandlers(
+          handleData: (i, sink) {
+            sink.add(i * 2);
+          });
+      var sink = transformer.bind(controller.sink);
+
+      var results = [];
+      controller.stream.listen(results.add, onDone: expectAsync(() {
+        expect(results, equals([2, 4, 6]));
+      }));
+
+      sink.add(1);
+      sink.add(2);
+      sink.add(3);
+      sink.close();
+    });
+
+    test("transforms error events", () {
+      var transformer = new StreamSinkTransformer.fromHandlers(
+          handleError: (i, stackTrace, sink) {
+            sink.addError(i * 2, stackTrace);
+          });
+      var sink = transformer.bind(controller.sink);
+
+      var results = [];
+      controller.stream.listen(expectAsync((_) {}, count: 0),
+          onError: (error, stackTrace) {
+            results.add(error);
+          },
+          onDone: expectAsync(() {
+            expect(results, equals([2, 4, 6]));
+          }));
+
+      sink.addError(1);
+      sink.addError(2);
+      sink.addError(3);
+      sink.close();
+    });
+
+    test("transforms done events", () {
+      var transformer = new StreamSinkTransformer.fromHandlers(
+          handleDone: (sink) {
+            sink.add(1);
+            sink.close();
+          });
+      var sink = transformer.bind(controller.sink);
+
+      var results = [];
+      controller.stream.listen(results.add, onDone: expectAsync(() {
+        expect(results, equals([1]));
+      }));
+
+      sink.close();
+    });
+
+    test("forwards the future from inner.close", () async {
+      var transformer = new StreamSinkTransformer.fromHandlers();
+      var innerSink = new CompleterStreamSink();
+      var sink = transformer.bind(innerSink);
+
+      // The futures shouldn't complete until the inner sink's close future
+      // completes.
+      var doneResult = new ResultFuture(sink.done);
+      doneResult.catchError((_) {});
+      var closeResult = new ResultFuture(sink.close());
+      closeResult.catchError((_) {});
+      await flushMicrotasks();
+      expect(doneResult.isComplete, isFalse);
+      expect(closeResult.isComplete, isFalse);
+
+      // Once the inner sink is completed, the futures should fire. 
+      innerSink.completer.complete();
+      await flushMicrotasks();
+      expect(doneResult.isComplete, isTrue);
+      expect(closeResult.isComplete, isTrue);
+    });
+
+    test("doesn't top-level the future from inner.close", () async {
+      var transformer = new StreamSinkTransformer.fromHandlers(
+          handleData: (_, sink) {
+            sink.close();
+          });
+      var innerSink = new CompleterStreamSink();
+      var sink = transformer.bind(innerSink);
+
+      // This will close the inner sink, but it shouldn't top-level the error.
+      sink.add(1);
+      innerSink.completer.completeError("oh no");
+      await flushMicrotasks();
+
+      // The error should be piped through done and close even if they're called
+      // after the underlying sink is closed.
+      expect(sink.done, throwsA("oh no"));
+      expect(sink.close(), throwsA("oh no"));
+    });
+  });
+}