Zip async correctness fix#129122
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…path ZipEndOfCentralDirectoryBlock.ReadBlockAsync called the synchronous Stream.ReadExactly when copying the archive comment after the EOCD header. This blocks the calling thread on the underlying stream and silently ignores the supplied CancellationToken. Switch to ReadExactlyAsync with ConfigureAwait(false), matching the rest of the async path. Adds a regression test using CallTrackingStream to verify the async open path never invokes the synchronous Stream.Read or ReadByte when reading an archive with a non-empty comment. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
…p-async-correctness-fix
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Tagging subscribers to this area: @karelz, @dotnet/area-system-io-compression |
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Pull request overview
Fixes async ZIP reading correctness by ensuring the archive comment is read asynchronously (avoiding synchronous Stream.Read* calls) on the async code path, and adds a regression test to validate the behavior.
Changes:
- Switch
ZipEndOfCentralDirectoryBlock.ReadBlockAsyncto useReadExactlyAsync(..., cancellationToken)when reading the archive-level comment. - Add a unit test that asserts
ZipArchive.CreateAsync(...)+ZipArchive.Commentdoes not invoke synchronousStream.Read/Stream.ReadByteon the provided stream.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| src/libraries/System.IO.Compression/src/System/IO/Compression/ZipBlocks.Async.cs | Replaces a synchronous ReadExactly with await ReadExactlyAsync(..., cancellationToken) to keep the async path fully async. |
| src/libraries/System.IO.Compression/tests/ZipArchive/zip_ReadTests.cs | Adds a regression test using CallTrackingStream to ensure async ZIP open + comment retrieval doesn’t call sync read APIs. |
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| ZipArchive readArchive = await ZipArchive.CreateAsync(tracker, ZipArchiveMode.Read, leaveOpen: true, entryNameEncoding: null); | ||
| Assert.Equal(ExpectedComment, readArchive.Comment); | ||
| await readArchive.DisposeAsync(); | ||
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iremyux
approved these changes
Jun 8, 2026
rzikm
approved these changes
Jun 8, 2026
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| await using MemoryStream ms = new MemoryStream(zipBytes); | ||
| await using CallTrackingStream tracker = new CallTrackingStream(ms); |
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I think there is something like AsyncOnlyStream that throws when any synchronous method is used that might be better fit for this kind of test.
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fix mix of sync/async reads when reading zip comment