Skip to content

Propagate cancellation token in async Merge #880

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
FreeApophis merged 2 commits into from
Sep 15, 2026
Merged

Propagate cancellation token in async Merge #880

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
7ccbe65
Propagate cancellation token in async Merge
wxxb789 Aug 10, 2026
3841ba3
Merge branch 'main' into async-merge-cancellation
FreeApophis Sep 15, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
7 changes: 7 additions & 0 deletions Funcky.Test/Extensions/AsyncEnumerableExtensions/MergeTest.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -76,5 +76,12 @@ public Task MergeASequenceWithADifferentComparer()

return AsyncAssert.Equal(expected, sequence1.Merge(sequence2, DescendingIntComparer.Create()));
}

[Fact]
public async Task CancellationIsPropagated()
{
var canceledToken = new CancellationToken(canceled: true);
_ = await new AssertIsCancellationRequestedAsyncSequence<Unit>().Merge(AsyncEnumerable.Empty<Unit>()).ToListAsync(canceledToken);
}
}
#endif
18 changes: 13 additions & 5 deletions Funcky/Extensions/AsyncEnumerableExtensions/Merge.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
#if INTEGRATED_ASYNC
using System.Collections.Immutable;
using System.Runtime.CompilerServices;

namespace Funcky.Extensions;

Expand Down Expand Up @@ -56,13 +57,20 @@ public static IAsyncEnumerable<TSource> Merge<TSource>(this IAsyncEnumerable<TSo
/// <typeparam name="TSource">The type elements in the sequences.</typeparam>
/// <returns>The merged sequences in the same order as the given sequences.</returns>
[Pure]
public static async IAsyncEnumerable<TSource> Merge<TSource>(this IEnumerable<IAsyncEnumerable<TSource>> sources, Option<IComparer<TSource>> comparer = default)
public static IAsyncEnumerable<TSource> Merge<TSource>(this IEnumerable<IAsyncEnumerable<TSource>> sources, Option<IComparer<TSource>> comparer = default)
=> MergeInternal(sources, comparer);

[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static async IAsyncEnumerable<TSource> MergeInternal<TSource>(
IEnumerable<IAsyncEnumerable<TSource>> sources,
Option<IComparer<TSource>> comparer,
[EnumeratorCancellation] CancellationToken cancellationToken = default)
{
var enumerators = GetMergeEnumerators(sources);
var enumerators = GetMergeEnumerators(sources, cancellationToken);

try
{
await foreach (var element in MergeEnumerators(enumerators.RemoveRange(await enumerators.ToAsyncEnumerable().Where(async (f, _) => await HasMoreElements(f).ConfigureAwait(false)).ToListAsync().ConfigureAwait(false)), GetMergeComparer(comparer)).ConfigureAwait(false))
await foreach (var element in MergeEnumerators(enumerators.RemoveRange(await enumerators.ToAsyncEnumerable().Where(async (f, _) => await HasMoreElements(f).ConfigureAwait(false)).ToListAsync(cancellationToken).ConfigureAwait(false)), GetMergeComparer(comparer)).ConfigureAwait(false))
{
yield return element;
}
Expand All @@ -76,8 +84,8 @@ public static async IAsyncEnumerable<TSource> Merge<TSource>(this IEnumerable<IA
}
}

private static ImmutableList<IAsyncEnumerator<TSource>> GetMergeEnumerators<TSource>(IEnumerable<IAsyncEnumerable<TSource>> sources)
=> ImmutableList.Create<IAsyncEnumerator<TSource>>().AddRange(sources.Select(s => s.GetAsyncEnumerator()));
private static ImmutableList<IAsyncEnumerator<TSource>> GetMergeEnumerators<TSource>(IEnumerable<IAsyncEnumerable<TSource>> sources, CancellationToken cancellationToken)
=> ImmutableList.Create<IAsyncEnumerator<TSource>>().AddRange(sources.Select(s => s.GetAsyncEnumerator(cancellationToken)));

private static IComparer<TSource> GetMergeComparer<TSource>(Option<IComparer<TSource>> comparer = default)
=> comparer.GetOrElse(Comparer<TSource>.Default);
Expand Down
Loading