public async Task AsyncExceptionIsPropagatedToGetNextCall()
{
TaskCompletionSource <int> tcs = new TaskCompletionSource <int>();
IAsyncEnumerator <int> enumerator = AwaitAndYieldItem();
AsyncItem <int> itemTask = enumerator.GetNextAsync();
tcs.SetException(new Exception("The punch has been spiked"));
Func <Task <Optional <int> > > awaitFaultyItemAct = async() => await itemTask;
awaitFaultyItemAct.ShouldThrow <Exception>();
Optional <int> itemAfterException = await enumerator.GetNextAsync().WithSyncContext();
itemAfterException.HasValue.Should().BeFalse();
async IAsyncEnumerator <int> AwaitAndYieldItem()
{
int awaitedItem = await tcs.Task.ConfigureAwait(false);
await AsyncYield.Item(awaitedItem);
return(await AsyncYield.Break <int>());
}
}
public async Task TrueAwaitsAreSupported()
{
const int expectedValue = 42;
TaskCompletionSource <int> tcs = new TaskCompletionSource <int>();
IAsyncEnumerator <int> enumerator = AwaitTaskThenYieldItem();
AsyncItem <int> nextItemTask = enumerator.GetNextAsync();
nextItemTask.IsCompleted.Should().BeFalse();
tcs.SetResult(expectedValue);
Optional <int> yieldedItem = await nextItemTask.WithSyncContext();
yieldedItem.HasValue.Should().BeTrue();
yieldedItem.Value.Should().Be(expectedValue);
async IAsyncEnumerator <int> AwaitTaskThenYieldItem()
{
int awaitedValue = await tcs.Task.ConfigureAwait(false);
await AsyncYield.Item(awaitedValue);
return(await AsyncYield.Break <int>());
}
}
public static Task <T> GetNextAsync <T>(this IAsyncEnumerator <T> @this, CancellationToken token)
{
return(@this.GetNextAsync().AsTask().ContinueWith <Task <T> >(
continuationFunction: ante => ante,
cancellationToken: token,
continuationOptions: TaskContinuationOptions.ExecuteSynchronously,
TaskScheduler.Default).Unwrap());
}
public void GetNextThrowsIfCalledBeforePreviousGetNextCompletes()
{
TaskCompletionSource <int>[] taskSources = Enumerable.Range(0, 2).Select(_ => new TaskCompletionSource <int>()).ToArray();
IAsyncEnumerator <int> enumerator = TaskDependentEnumerator();
AsyncItem <int> firstItemTask = enumerator.GetNextAsync();
Func <Task <Optional <int> > > despicableAct = async() => await enumerator.GetNextAsync();
despicableAct.ShouldThrow <PreviousItemNotCompletedException>();
async IAsyncEnumerator <int> TaskDependentEnumerator()
{
foreach (TaskCompletionSource <int> tcs in taskSources)
{
int item = await tcs.Task.ConfigureAwait(false);
await AsyncYield.Item(item);
}
return(await AsyncYield.Break <int>());
}
}
public static async Task ForEach <TItem, TState>(this IAsyncEnumerator <TItem> asyncEnumerator, TState state, Action <TItem, TState> action)
{
while (true)
{
Optional <TItem> item = await asyncEnumerator.GetNextAsync();
if (!item.HasValue)
{
break;
}
action(item.Value, state);
}
}
public async Task SynchronousExceptionIsPropagatedToGetNextCall()
{
const int expectedValue = 42;
IAsyncEnumerator <int> enumerator = YieldItemThenThrow();
Optional <int> item = await enumerator.GetNextAsync().WithSyncContext();
item.Value.Should().Be(expectedValue);
Func <Task <Optional <int> > > nextItemAct = async() => await enumerator.GetNextAsync();
nextItemAct.ShouldThrow <Exception>();
Optional <int> itemAfterException = await enumerator.GetNextAsync().WithSyncContext();
itemAfterException.HasValue.Should().BeFalse();
async IAsyncEnumerator <int> YieldItemThenThrow()
{
await AsyncYield.Item(expectedValue);
throw new Exception("All you enumerator are belong to us");
}
}
public async Task CanCallGetNextAsyncInfinitelyAfterSequenceHasEnded()
{
IAsyncEnumerator <int> enumerator = EmptyEnumerator();
for (int i = 0; i < 10; i++)
{
Optional <int> asyncItem = await enumerator.GetNextAsync().WithSyncContext();
asyncItem.HasValue.Should().BeFalse();
}
async IAsyncEnumerator <int> EmptyEnumerator()
{
return(await AsyncYield.Break <int>());
}
}
public async Task ExecutionDoesNotStartUntilNextAsyncIsCalled()
{
bool executionStarted = false;
IAsyncEnumerator <int> enumerator = SideEffectEnumerator();
executionStarted.Should().BeFalse();
Optional <int> nextItem = await enumerator.GetNextAsync().WithSyncContext();
executionStarted.Should().BeTrue();
async IAsyncEnumerator <int> SideEffectEnumerator()
{
executionStarted = true;
await AsyncYield.Item(42);
return(await AsyncYield.Break <int>());
}
}
