lib/src/frontend/future_matchers.dart

// Copyright (c) 2012, 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:matcher/matcher.dart';

import '../backend/invoker.dart';
import 'expect.dart';

/// Matches a [Future] that completes successfully with a value.
///
/// Note that this creates an asynchronous expectation. The call to `expect()`
/// that includes this will return immediately and execution will continue.
/// Later, when the future completes, the actual expectation will run.
///
/// To test that a Future completes with an exception, you can use [throws] and
/// [throwsA].
final Matcher completes = const _Completes(null);

/// Matches a [Future] that completes succesfully with a value that matches
/// [matcher].
///
/// Note that this creates an asynchronous expectation. The call to
/// `expect()` that includes this will return immediately and execution will
/// continue. Later, when the future completes, the actual expectation will run.
///
/// To test that a Future completes with an exception, you can use [throws] and
/// [throwsA].
///
/// The [description] parameter is deprecated and shouldn't be used.
Matcher completion(matcher, [@deprecated String description]) =>
    new _Completes(wrapMatcher(matcher));

class _Completes extends Matcher {
  final Matcher _matcher;

  const _Completes(this._matcher);

  bool matches(item, Map matchState) {
    if (item is! Future) return false;
    Invoker.current.addOutstandingCallback();

    item.then((value) {
      if (_matcher != null) expect(value, _matcher);
      Invoker.current.removeOutstandingCallback();
    });

    return true;
  }

  Description describe(Description description) {
    if (_matcher == null) {
      description.add('completes successfully');
    } else {
      description.add('completes to a value that ').addDescriptionOf(_matcher);
    }
    return description;
  }
}