Tutorial(streams): update for Dart 2 and analayze/test code

Contributes to #407, #637, #664

examples/misc/lib/tutorial/cat_no_hash.dart

@@ -0,0 +1,14 @@
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+Future<void> main(List<String> args) async {
+  var file = new File(args[0]);
+  var lines = file
+      .openRead()
+      .transform(utf8.decoder) //!<br>
+      .transform(const LineSplitter());
+  await for (var line in lines) {
+    if (!line.startsWith('#')) print(line);
+  }
+}

examples/misc/lib/tutorial/misc.dart

@@ -1,4 +1,4 @@
-// ignore_for_file: type_annotate_public_apis, unused_element
+// ignore_for_file: annotate_overrides, type_annotate_public_apis, unused_element
 // NOTE: Declarations in this file are analyzed but not tested.
 
 import 'dart:async';
@@ -33,3 +33,50 @@ void futuresTutorial() {
       .catchError((e) => handleError(e));
   // #enddocregion Future-wait
 }
+
+void streamsTutorial() {
+  // #docregion lastPositive
+  Future<int> lastPositive(Stream<int> stream) =>
+      stream.lastWhere((x) => x >= 0);
+  // #enddocregion lastPositive
+
+  void log(e) {}
+
+  // #docregion mapLogErrors
+  Stream<S> mapLogErrors<S, T>(
+    Stream<T> stream,
+    S Function(T event) convert,
+  ) async* {
+    var streamWithoutErrors = stream.handleError((e) => log(e));
+    await for (var event in streamWithoutErrors) {
+      yield convert(event);
+    }
+  }
+  // #enddocregion mapLogErrors
+}
+
+abstract class MyStream<T> extends Stream<T> {
+  // #docregion mock-stream-method-implementations
+  Future<bool> contains(Object needle) async {
+    await for (var event in this) {
+      if (event == needle) return true;
+    }
+    return false;
+  }
+
+  Future forEach(void Function(T element) action) async {
+    await for (var event in this) {
+      action(event);
+    }
+  }
+
+  Future<List<T>> toList() async {
+    final result = <T>[];
+    await this.forEach(result.add);
+    return result;
+  }
+
+  Future<String> join([String separator = ""]) async =>
+      (await this.toList()).join(separator);
+  // #enddocregion mock-stream-method-implementations
+}

examples/misc/lib/tutorial/stream_interface.dart

@@ -0,0 +1,60 @@
+// ignore_for_file: annotate_overrides, type_annotate_public_apis
+import 'dart:async';
+
+// TODO(chalin): I believe that handleError's test argument should be declared
+// as follows, but it isn't: {bool Function(dynamic error) test}.
+
+abstract class MyStream<T> implements Stream<T> {
+  // #docregion main-stream-members
+  Future<T> get first;
+  Future<bool> get isEmpty;
+  Future<T> get last;
+  Future<int> get length;
+  Future<T> get single;
+  Future<bool> any(bool Function(T element) test);
+  Stream<E> asyncExpand<E>(Stream<E> Function(T event) convert);
+  Stream<E> asyncMap<E>(FutureOr<E> Function(T event) convert);
+  Stream<R> cast<R>();
+  Future<bool> contains(Object needle);
+  Stream<T> distinct([bool Function(T previous, T next) equals]);
+  Future<E> drain<E>([E futureValue]);
+  Future<T> elementAt(int index);
+  Future<bool> every(bool Function(T element) test);
+  Stream<S> expand<S>(Iterable<S> Function(T element) convert);
+  Future<T> firstWhere(bool Function(T element) test, {T Function() orElse});
+  Future<S> fold<S>(S initialValue, S Function(S previous, T element) combine);
+  Future forEach(void Function(T element) action);
+  Future<String> join([String separator = ""]);
+  Future<T> lastWhere(bool Function(T element) test, {T Function() orElse});
+  Stream<S> map<S>(S Function(T event) convert);
+  Future pipe(StreamConsumer<T> streamConsumer);
+  Future<T> reduce(T Function(T previous, T element) combine);
+  Stream<R> retype<R>();
+  Future<T> singleWhere(bool Function(T element) test, {T Function() orElse});
+  Stream<T> skip(int count);
+  Stream<T> skipWhile(bool Function(T element) test);
+  Stream<T> take(int count);
+  Stream<T> takeWhile(bool Function(T element) test);
+  Future<List<T>> toList();
+  Future<Set<T>> toSet();
+  Stream<T> where(bool Function(T event) test);
+  // #enddocregion main-stream-members
+
+  bool get isBroadcast;
+
+  Stream<T> asBroadcastStream(
+      {void Function(StreamSubscription<T> subscription) onListen,
+      void Function(StreamSubscription<T> subscription) onCancel});
+
+  // #docregion special-stream-members
+  Stream<T> handleError(Function onError, {bool test(error)});
+  Stream<T> timeout(Duration timeLimit,
+      {void Function(EventSink<T> sink) onTimeout});
+  Stream<S> transform<S>(StreamTransformer<T, S> streamTransformer);
+  // #enddocregion special-stream-members
+
+  // #docregion listen
+  StreamSubscription<T> listen(void Function(T event) onData,
+      {Function onError, void Function() onDone, bool cancelOnError});
+  // #enddocregion listen
+}

examples/misc/lib/tutorial/sum_stream.dart

@@ -0,0 +1,25 @@
+// ignore_for_file: type_annotate_public_apis
+// #docregion
+import 'dart:async';
+
+// #docregion sumStream
+Future<int> sumStream(Stream<int> stream) async {
+  var sum = 0;
+  await for (var value in stream) {
+    sum += value;
+  }
+  return sum;
+}
+// #enddocregion sumStream
+
+Stream<int> countStream(int to) async* {
+  for (int i = 1; i <= to; i++) {
+    yield i;
+  }
+}
+
+main() async {
+  var stream = countStream(10);
+  var sum = await sumStream(stream);
+  print(sum); // 55
+}

examples/misc/lib/tutorial/sum_stream_with_catch.dart

@@ -0,0 +1,31 @@
+// ignore_for_file: type_annotate_public_apis
+// #docregion
+import 'dart:async';
+
+Future<int> sumStream(Stream<int> stream) async {
+  var sum = 0;
+  try {
+    await for (var value in stream) {
+      sum += value;
+    }
+  } catch (e) {
+    return -1;
+  }
+  return sum;
+}
+
+Stream<int> countStream(int to) async* {
+  for (int i = 1; i <= to; i++) {
+    if (i == 4) {
+      throw new Exception('Intentional exception');
+    } else {
+      yield i;
+    }
+  }
+}
+
+main() async {
+  var stream = countStream(10);
+  var sum = await sumStream(stream);
+  print(sum); // -1
+}

examples/misc/test/tutorial/streams_test.dart

@@ -0,0 +1,11 @@
+// ignore_for_file: type_annotate_public_apis
+import 'package:test/test.dart';
+import 'package:examples/tutorial/sum_stream.dart' as sum_stream;
+import 'package:examples/tutorial/sum_stream_with_catch.dart'
+    as sum_stream_with_catch;
+
+void main() {
+  test('sumStream', () => expect(sum_stream.main, prints('55\n')));
+  test('sumStream with catch',
+      () => expect(sum_stream_with_catch.main, prints('-1\n')));
+}