tests/language/async_star_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.

library async_star_test;

import "package:unittest/unittest.dart";
import "dart:async";

main() {
  group("basic", () {
    test("empty", () {
      f() async* {}
      return f().toList().then((v) {
        expect(v, equals([]));
      });
    });

    test("single", () {
      f() async* { yield 42; }
      return f().toList().then((v) {
        expect(v, equals([42]));
      });
    });

    test("call delays", () {
      var list = [];
      f() async* { list.add(1); yield 2; }
      var res = f().forEach(list.add);
      list.add(0);
      return res.whenComplete(() {
        expect(list, equals([0, 1, 2]));
      });
    });

    test("throws", () {
      f() async* { yield 1; throw 2; }
      var completer = new Completer();
      var list = [];
      f().listen(list.add,
                 onError: (v) => list.add("$v"),
                 onDone: completer.complete);
      return completer.future.whenComplete(() {
        expect(list, equals([1, "2"]));
      });
    });

    test("multiple", () {
      f() async* {
        for (int i = 0; i < 10; i++) {
          yield i;
        }
      }
      return expectList(f(), new List.generate(10, id));
    });

    test("allows await", () {
      f() async* {
        var x = await new Future.value(42);
        yield x;
        x = await new Future.value(42);
      }
      return expectList(f(), [42]);
    });

    test("allows await in loop", () {
      f() async* {
        for (int i = 0; i < 10; i++) {
          yield await i;
        }
      }
      return expectList(f(), new List.generate(10, id));
    });

    test("allows yield*", () {
      f() async* {
        yield* new Stream.fromIterable([1, 2, 3]);
      }
      return expectList(f(), [1, 2, 3]);
    });

    test("allows yield* of async*", () {
      f(n) async* {
        yield n;
        if (n == 0) return;
        yield* f(n - 1);
        yield n;
      }
      return expectList(f(3), [3, 2, 1, 0, 1, 2, 3]);
    });

    test("Cannot yield* non-stream", () {
      f(s) async* {
        yield* s;
      }
      return f(42).transform(getErrors).single.then((v) {
        // Not implementing Stream.
        expect(v is Error, isTrue);
      });
    });

   test("Cannot yield* non-stream", () {
      f(s) async* {
        yield* s;
      }
      return f(new NotAStream()).transform(getErrors).single.then((v) {
        // Not implementing Stream.
        expect(v is Error, isTrue);
      });
    });
  });

  group("yield statement context", () {
    test("plain", () {
      f() async* {
        yield 0;
      }
      return expectList(f(), [0]);
    });

    test("if-then-else", () {
      f(b) async* {
        if (b) yield 0; else yield 1;
      }
      return expectList(f(true), [0]).whenComplete(() {
        expectList(f(false), [1]);
      });
    });

    test("block", () {
      f() async* {
        yield 0;
        { yield 1; }
        yield 2;
      }
      return expectList(f(), [0, 1, 2]);
    });

    test("labeled", () {
      f() async* {
        label1: yield 0;
      }
      return expectList(f(), [0]);
    });

    test("for-loop", () {
      f() async* {
        for (int i = 0; i < 3; i++) yield i;
      }
      return expectList(f(), [0, 1, 2]);
    });

    test("for-in-loop", () {
      f() async* {
        for (var i in [0, 1, 2]) yield i;
      }
      return expectList(f(), [0, 1, 2]);
    });

    test("await for-in-loop", () {
      f() async* {
        await for (var i in new Stream.fromIterable([0, 1, 2])) yield i;
      }
      return expectList(f(), [0, 1, 2]);
    });

    test("while-loop", () {
      f() async* {
        int i = 0;
        while (i < 3) yield i++;
      }
      return expectList(f(), [0, 1, 2]);
    });

    test("do-while-loop", () {
      f() async* {
        int i = 0;
        do yield i++; while (i < 3);
      }
      return expectList(f(), [0, 1, 2]);
    });

    test("try-catch-finally", () {
      f() async* {
        try { yield 0; } catch (e) { yield 1; } finally { yield 2; }
      }
      return expectList(f(), [0, 2]);
    });

    test("try-catch-finally 2", () {
      f() async* {
        try { yield throw 0; } catch (e) { yield 1; } finally { yield 2; }
      }
      return expectList(f(), [1, 2]);
    });

    test("switch-case", () {
      f(v) async* {
        switch (v) {
          case 0:
            yield 0;
            continue label1;
          label1:
          case 1:
            yield 1;
            break;
          default:
            yield 2;
        }
      }
      return expectList(f(0), [0, 1]).whenComplete(() {
        return expectList(f(1), [1]);
      }).whenComplete(() {
        return expectList(f(2), [2]);
      });
    });

    test("dead-code return", () {
      f() async* {
        return;
        yield 1;
      }
      return expectList(f(), []);
    });

    test("dead-code throw", () {
      f() async* {
        try {
          throw 0;
          yield 1;
        } catch (_) {}
      }
      return expectList(f(), []);
    });

    test("dead-code break", () {
      f() async* {
        while (true) {
          break;
          yield 1;
        }
      }
      return expectList(f(), []);
    });

    test("dead-code break 2", () {
      f() async* {
        label: {
          break label;
          yield 1;
        }
      }
      return expectList(f(), []);
    });

    test("dead-code continue", () {
      f() async* {
        do {
          continue;
          yield 1;
        } while (false);
      }
      return expectList(f(), []);
    });
  });

  group("yield expressions", () {
    test("local variable", () {
      f() async* {
        var x = 42;
        yield x;
      }
      return expectList(f(), [42]);
    });

    test("constant variable", () {
      f() async* {
        const x = 42;
        yield x;
      }
      return expectList(f(), [42]);
    });

    test("function call", () {
      g() => 42;
      f() async* {
        yield g();
      }
      return expectList(f(), [42]);
    });

    test("unary operator", () {
      f() async* {
        var x = -42;
        yield -x;
      }
      return expectList(f(), [42]);
    });

    test("binary operator", () {
      f() async* {
        var x = 21;
        yield x + x;
      }
      return expectList(f(), [42]);
    });

    test("ternary operator", () {
      f() async* {
        var x = 21;
        yield x == 21 ? x + x : x;
      }
      return expectList(f(), [42]);
    });

    test("suffix post-increment", () {
      f() async* {
        var x = 42;
        yield x++;
      }
      return expectList(f(), [42]);
    });

    test("suffix pre-increment", () {
      f() async* {
        var x = 41;
        yield ++x;
      }
      return expectList(f(), [42]);
    });

    test("assignment", () {
      f() async* {
        var x = 37;
        yield x = 42;
      }
      return expectList(f(), [42]);
    });

    test("assignment op", () {
      f() async* {
        var x = 41;
        yield x += 1;
      }
      return expectList(f(), [42]);
    });

    test("await", () {
      f() async* {
        yield await new Future.value(42);
      }
      return expectList(f(), [42]);
    });

    test("index operator", () {
      f() async* {
        var x = [42];
        yield x[0];
      }
      return expectList(f(), [42]);
    });

    test("function expression block", () {
      var o = new Object();
      f() async* {
        yield () { return o; };
      }
      return f().first.then((v) {
        expect(v(), same(o));
      });
    });

    test("function expression arrow", () {
      var o = new Object();
      f() async* {
        yield () => o;
      }
      return f().first.then((v) {
        expect(v(), same(o));
      });
    });

    test("function expression block async", () {
      var o = new Object();
      f() async* {
        yield () async { return o; };
      }
      return f().first.then((v) => v()).then((v) {
        expect(v, same(o));
      });
    });

    test("function expression arrow async", () {
      var o = new Object();
      f() async* {
        yield () async => o;
      }
      return f().first.then((v) => v()).then((v) {
        expect(v, same(o));
      });
    });

    test("function expression block async*", () {
      var o = new Object();
      f() async* {
        yield () async* { yield o; };
      }
      return f().first.then((v) => v().first).then((v) {
        expect(v, same(o));
      });
    });
  });

  group("loops", () {
    test("simple yield", () {
      f() async* {
        for (int i = 0; i < 3; i++) {
          yield i;
        }
      }
      return expectList(f(), [0, 1, 2]);
    });

    test("yield in double loop", () {
      f() async* {
        for (int i = 0; i < 3; i++) {
          for (int j = 0; j < 2; j++) {
            yield i * 2 + j;
          }
        }
      }
      return expectList(f(), [0, 1, 2, 3, 4, 5]);
    });

    test("yield in try body", () {
      var list = [];
      f() async* {
        for (int i = 0; i < 3; i++) {
          try {
            yield i;
          } finally {
            list.add("$i");
          }
        }
      }
      return expectList(f(), [0, 1, 2]).whenComplete(() {
        expect(list, equals(["0", "1", "2"]));
      });
    });

    test("yield in catch", () {
      var list = [];
      f() async* {
        for (int i = 0; i < 3; i++) {
          try {
            throw i;
          } catch (e) {
            yield e;
          } finally {
            list.add("$i");
          }
        }
      }
      return expectList(f(), [0, 1, 2]).whenComplete(() {
        expect(list, equals(["0", "1", "2"]));
      });
    });

    test("yield in finally", () {
      var list = [];
      f() async* {
        for (int i = 0; i < 3; i++) {
          try {
            throw i;
          } finally {
            yield i;
            list.add("$i");
            continue;
          }
        }
      }
      return expectList(f(), [0, 1, 2]).whenComplete(() {
        expect(list, equals(["0", "1", "2"]));
      });
    });

    test("keep yielding after cancel", () {
      f() async* {
        for (int i = 0; i < 10; i++) {
          try {
            yield i;
          } finally {
            continue;
          }
        }
      }
      return expectList(f().take(3), [0, 1, 2]);
    });
  });

  group("canceling", () {
    // Stream.take(n) automatically cancels after seeing the n'th value.

    test("cancels at yield", () {
      Completer exits = new Completer();
      var list = [];
      f() async* {
        try {
          list.add(0);
          yield list.add(1);
          list.add(2);
        } finally {
          exits.complete(3);
        }
      }
      // No events must be fired synchronously in response to a listen.
      var subscription = f().listen((v) { fail("Received event $v"); },
                                   onDone: () { fail("Received done"); });
      // No events must be delivered after a cancel.
      subscription.cancel();
      return exits.future.then((v) {
        expect(v, equals(3));
        expect(list, equals([0, 1]));
      });
    });

    test("does cancel eventually", () {
      var exits = new Completer();
      var list = [];
      f() async* {
        int i = 0;
        try {
          while (true) yield i++;
        } finally {
          list.add("a");
          exits.complete(i);
        }
      }
      return expectList(f().take(5), [0, 1, 2, 3, 4])
          .then((_) => exits.future)
          .then((v) {
            expect(v, greaterThan(4));
            expect(list, ["a"]);
          });
    });

    group("at index", () {
      f() async* {
        try {
          yield await new Future.microtask(() => 1);
        } finally {
          try {
            yield await new Future.microtask(() => 2);
          } finally {
            yield await new Future.microtask(() => 3);
          }
        }
      }
      test("- all, sanity check", () {
        return expectList(f(), [1, 2, 3]);
      });
      test("after end", () {
        return expectList(f().take(4), [1, 2, 3]);
      });
      test("at end", () {
        return expectList(f().take(3), [1, 2, 3]);
      });
      test("before end", () {
        return expectList(f().take(2), [1, 2]);
      });
      test("early", () {
        return expectList(f().take(1), [1]);
      });
      test("at start", () {
        return expectList(f().take(0), []);
      });
    });
  });

  group("pausing", () {
    test("pauses execution at yield for at least a microtask", () {
      var list = [];
      f() async* {
        list.add(1);
        yield 2;
        list.add(3);
        yield 4;
        list.add(5);
      }
      var done = new Completer();
      var sub = f().listen((v) {
        if (v == 2) {
          expect(list, equals([1]));
        } else if (v == 4) {
          expect(list, equals([1, 3]));
        } else {
          fail("Unexpected value $v");
        }
      }, onDone: () {
        expect(list, equals([1, 3, 5]));
        done.complete();
      });
      return done.future;
    });

    test("pause stops execution at yield", () {
      var list = [];
      f() async* {
        list.add(1);
        yield 2;
        list.add(3);
        yield 4;
        list.add(5);
      }
      var done = new Completer();
      var sub;
      sub = f().listen((v) {
        if (v == 2) {
          expect(list, equals([1]));
          sub.pause();
          new Timer(MS * 300, () {
            expect(list.length, lessThan(3));
            sub.resume();
          });
        } else if (v == 4) {
          expect(list, equals([1, 3]));
        } else {
          fail("Unexpected value $v");
        }
      }, onDone: () {
        expect(list, equals([1, 3, 5]));
        done.complete();
      });
      return done.future;
    });

    test("pause stops execution at yield 2", () {
      var list = [];
      f() async* {
        int i = 0;
        while (true) {
          yield i;
          list.add(i);
          i++;
        }
      }
      int expected = 0;
      var done = new Completer();
      var sub;
      sub = f().listen((v) {
        expect(v, equals(expected++));
        if (v % 5 == 0) {
          sub.pause(new Future.delayed(MS * 300));
        } else if (v == 17) {
          sub.cancel();
          done.complete();
        }
      }, onDone: () {
        fail("Unexpected done!");
      });
      return done.future.whenComplete(() {
        expect(list.length == 18 || list.length == 19, isTrue);
      });
    });
  });

  group("await for", () {
    mkStream(int n) async* {
      for (int i = 0; i < n; i++) yield i;
    }

    test("simple stream", () {
      f(s) async {
        var r = 0;
        await for(var v in s) r += v;
        return r;
      }
      return f(mkStream(5)).then((v) {
        expect(v, equals(10));
      });
    });

    test("simple stream, await", () {
      f(s) async {
        var r = 0;
        await for(var v in s) r += await new Future.microtask(() => v);
        return r;
      }
      return f(mkStream(5)).then((v) {
        expect(v, equals(10));
      });
    });

    test("simple stream reyield", () {
      f(s) async* {
        var r = 0;
        await for(var v in s) yield r += v;
      }
      return expectList(f(mkStream(5)), [0, 1, 3, 6, 10]);
    });

    test("simple stream, await, reyield", () {
      f(s) async* {
        var r = 0;
        await for(var v in s) yield r += await new Future.microtask(() => v);
      }
      return expectList(f(mkStream(5)), [0, 1, 3, 6, 10]);
    });

    test("nested", () {
      f() async {
        var r = 0;
        await for (var i in mkStream(5)) {
          await for (var j in mkStream(3)) {
            r += i * j;
          }
        }
        return r;
      }
      return f().then((v) {
        expect(v, equals((1 + 2 + 3 + 4) * (1 + 2)));
      });
    });

    test("nested, await", () {
      f() async {
        var r = 0;
        await for (var i in mkStream(5)) {
          await for (var j in mkStream(3)) {
            r += await new Future.microtask(() => i * j);
          }
        }
        return r;
      }
      return f().then((v) {
        expect(v, equals((1 + 2 + 3 + 4) * (1 + 2)));
      });
    });

    test("nested, await * 2", () {
      f() async {
        var r = 0;
        await for (var i in mkStream(5)) {
          var ai = await new Future.microtask(() => i);
          await for (var j in mkStream(3)) {
            r += await new Future.microtask(() => ai * j);
          }
        }
        return r;
      }
      return f().then((v) {
        expect(v, equals((1 + 2 + 3 + 4) * (1 + 2)));
      });
    });
  });
}

// Obscuring identity function.
id(x) {
  try {
    if (x != null) throw x;
  } catch (e) {
    return e;
  }
  return null;
}

expectList(stream, list) {
  return stream.toList().then((v) {
    expect(v, equals(list));
  });
}

const MS = const Duration(milliseconds: 1);

var getErrors = new StreamTransformer.fromHandlers(
  handleData:(data, sink) { fail("Unexpected value"); },
  handleError: (e, s, sink) { sink.add(e); },
  handleDone: (sink) { sink.close(); });

class NotAStream {
  listen(oData, {onError, onDone, cancelOnError}) {
    fail("Not implementing Stream.");
  }
}