fix: handle shared file contents across handles#1507
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Each MockFileStream kept its own MemoryStream buffer that was only synced to the shared MockFileData.Contents on flush, so a second handle opened with FileShare.ReadWrite never saw writes made through another handle. On top of that, InternalFlush unconditionally wrote its buffer back, so a read-only handle's Flush could clobber another handle's writes. Track the last-synced Contents reference and reload the buffer from it on every read entry point (Read, ReadByte, ReadAsync, span overloads) when another handle has replaced it. InternalFlush now writes back only when the buffer actually differs from the last synced snapshot, matching the no-op behavior of a real FileStream.Flush with no pending writes.
Test Results 31 files ± 0 31 suites ±0 17s ⏱️ -4s For more details on these failures, see this check. Results for commit 7b85ec1. ± Comparison against base commit 9cb6266. ♻️ This comment has been updated with latest results. |
The shared-contents regression test ignored the byte count returned by Stream.Read, which the analyzer flags as CA2022 (inexact read) and the build treats as an error. Capture the count and assert it equals the requested length.
The shared-contents fix added public overrides to MockFileStream (ReadByte and ReadAsync(byte[]) on all frameworks; Read(Span) and ReadAsync(Memory) where FEATURE_SPAN is defined). Regenerate the expected public API surface via the AcceptApiChanges test so VerifyPublicApiForTestingHelpers passes.
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This is addressed in release v22.2.0. |
This was referenced Jul 12, 2026
This was referenced Jul 13, 2026
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Each MockFileStream kept its own MemoryStream buffer that was only synced to the shared MockFileData.Contents on flush, so a second handle opened with FileShare.ReadWrite never saw writes made through another handle. On top of that, InternalFlush unconditionally wrote its buffer back, so a read-only handle's Flush could clobber another handle's writes.
Track the last-synced Contents reference and reload the buffer from it on every read entry point (Read, ReadByte, ReadAsync, span overloads) when another handle has replaced it. InternalFlush now writes back only when the buffer actually differs from the last synced snapshot, matching the no-op behavior of a real FileStream.Flush with no pending writes.