Move Zstandard APIs from System.IO.Compression.Zstandard to System.IO.Compression by rzikm · Pull Request #124634 · dotnet/runtime

rzikm · 2026-02-20T10:42:55Z

There is no real benefit from having the APIs in separate assembly because:

the Managed code size is rather small
it P/Invokes System.IO.Compression.Native just like System.IO.Compression managed assembly does
It would lead to circular dependency if we decide to implement Support Zstandard compression in ZipArchives #123532

….Compression Move Zstandard compression/decompression APIs from the separate System.IO.Compression.Zstandard assembly into the main System.IO.Compression assembly for better organization. Changes: - Move source files to src/System/IO/Compression/Zstandard/ subdirectory - Move test files to tests/Zstandard/ subdirectory - Add PNSE stubs for browser/wasi platforms - Update ref API with [UnsupportedOSPlatform] attributes - Merge resource strings into System.IO.Compression Strings.resx - Remove System.IO.Compression.Zstandard project reference from System.Net.Http - Remove System.IO.Compression.Zstandard from NetCoreAppLibrary.props and sfx.slnx - Delete the old System.IO.Compression.Zstandard directory Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

dotnet-policy-service · 2026-02-20T10:44:08Z

Tagging subscribers to this area: @karelz, @dotnet/area-system-io-compression
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

This PR consolidates Zstandard compression APIs into the main System.IO.Compression library, removing the separate System.IO.Compression.Zstandard assembly and updating build/test infrastructure accordingly.

Changes:

Move Zstandard implementation and tests under System.IO.Compression (including ref API surface updates).
Add browser/WASI PlatformNotSupportedException stubs while keeping full implementations on Windows/Unix TFMs.
Remove the old System.IO.Compression.Zstandard project artifacts and references (solutions, props, project references).

Reviewed changes

Copilot reviewed 23 out of 31 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/libraries/sfx.slnx	Removes `System.IO.Compression.Zstandard` ref project from the libraries solution.
src/libraries/System.Net.Http/src/System.Net.Http.csproj	Drops project reference to the removed `System.IO.Compression.Zstandard` project.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardTestUtils.cs	Adds shared helpers for Zstandard tests in the consolidated test project.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardEncoderDecoderTests.cs	Adds encoder/decoder coverage to `System.IO.Compression` tests.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardDictionaryTests.cs	Adds dictionary creation/training tests under `System.IO.Compression`.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardCompressionOptionsTests.cs	Adds validation tests for `ZstandardCompressionOptions`.
src/libraries/System.IO.Compression/tests/Zstandard/CompressionStreamUnitTests.Zstandard.cs	Adds `ZstandardStream` coverage integrated with existing stream test base.
src/libraries/System.IO.Compression/tests/System.IO.Compression.Tests.csproj	Integrates Zstandard test sources conditionally (excluding browser/WASI).
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardUtils.cs	Adds shared internal helpers for Zstandard implementation.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.cs	Adds platform attributes on `ZstandardStream`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.Decompress.cs	Adds decompression-side stream implementation under the consolidated assembly.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.Compress.cs	Adds compression-side stream implementation under the consolidated assembly.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardEncoder.cs	Adds platform attributes on `ZstandardEncoder`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardDictionary.cs	Adds platform attributes on `ZstandardDictionary`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardDecoder.cs	Adds platform attributes on `ZstandardDecoder`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardCompressionOptions.cs	Adds platform attributes on `ZstandardCompressionOptions`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/Zstandard.PlatformNotSupported.cs	Adds browser/WASI stubs throwing `PlatformNotSupportedException`.
src/libraries/System.IO.Compression/src/System.IO.Compression.csproj	Multi-target integration for Zstandard sources + stubs under `System.IO.Compression`.
src/libraries/System.IO.Compression/src/Resources/Strings.resx	Merges Zstandard resource strings into `System.IO.Compression` resources.
src/libraries/System.IO.Compression/ref/System.IO.Compression.cs	Adds Zstandard APIs to the `System.IO.Compression` reference surface with platform attributes.
src/libraries/System.IO.Compression/README.md	Updates README to reflect Zstandard support in `System.IO.Compression`.
src/libraries/System.IO.Compression/Directory.Build.props	Removes BOM/normalizes file header.
src/libraries/System.IO.Compression.Zstandard/tests/System.IO.Compression.Zstandard.Tests.csproj	Deletes old Zstandard test project (now integrated into `System.IO.Compression` tests).
src/libraries/System.IO.Compression.Zstandard/src/System.IO.Compression.Zstandard.csproj	Deletes old Zstandard implementation project (now merged into `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/src/Resources/Strings.resx	Deletes old resource file (strings moved to `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/ref/System.IO.Compression.Zstandard.csproj	Deletes old ref project.
src/libraries/System.IO.Compression.Zstandard/ref/System.IO.Compression.Zstandard.cs	Deletes old ref surface file (moved into `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/System.IO.Compression.Zstandard.slnx	Deletes old solution for the removed library.
src/libraries/System.IO.Compression.Zstandard/README.md	Deletes old library README (functionality now documented under `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/Directory.Build.props	Deletes old build props (no longer needed after consolidation).
src/libraries/NetCoreAppLibrary.props	Removes `System.IO.Compression.Zstandard` from the NetCoreApp library list.

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 23 out of 31 changed files in this pull request and generated 1 comment.

iremyux

LGTM

….Compression (dotnet#124634) There is no real benefit from having the APIs in separate assembly because: - the Managed code size is rather small - it P/Invokes System.IO.Compression.Native just like System.IO.Compression managed assembly does - It would lead to circular dependency if we decide to implement dotnet#123532 --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

rzikm · 2026-02-20T10:42:55Z

There is no real benefit from having the APIs in separate assembly because:

the Managed code size is rather small
it P/Invokes System.IO.Compression.Native just like System.IO.Compression managed assembly does
It would lead to circular dependency if we decide to implement Support Zstandard compression in ZipArchives #123532

….Compression Move Zstandard compression/decompression APIs from the separate System.IO.Compression.Zstandard assembly into the main System.IO.Compression assembly for better organization. Changes: - Move source files to src/System/IO/Compression/Zstandard/ subdirectory - Move test files to tests/Zstandard/ subdirectory - Add PNSE stubs for browser/wasi platforms - Update ref API with [UnsupportedOSPlatform] attributes - Merge resource strings into System.IO.Compression Strings.resx - Remove System.IO.Compression.Zstandard project reference from System.Net.Http - Remove System.IO.Compression.Zstandard from NetCoreAppLibrary.props and sfx.slnx - Delete the old System.IO.Compression.Zstandard directory Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

dotnet-policy-service · 2026-02-20T10:44:08Z

Tagging subscribers to this area: @karelz, @dotnet/area-system-io-compression
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

This PR consolidates Zstandard compression APIs into the main System.IO.Compression library, removing the separate System.IO.Compression.Zstandard assembly and updating build/test infrastructure accordingly.

Changes:

Move Zstandard implementation and tests under System.IO.Compression (including ref API surface updates).
Add browser/WASI PlatformNotSupportedException stubs while keeping full implementations on Windows/Unix TFMs.
Remove the old System.IO.Compression.Zstandard project artifacts and references (solutions, props, project references).

Reviewed changes

Copilot reviewed 23 out of 31 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/libraries/sfx.slnx	Removes `System.IO.Compression.Zstandard` ref project from the libraries solution.
src/libraries/System.Net.Http/src/System.Net.Http.csproj	Drops project reference to the removed `System.IO.Compression.Zstandard` project.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardTestUtils.cs	Adds shared helpers for Zstandard tests in the consolidated test project.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardEncoderDecoderTests.cs	Adds encoder/decoder coverage to `System.IO.Compression` tests.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardDictionaryTests.cs	Adds dictionary creation/training tests under `System.IO.Compression`.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardCompressionOptionsTests.cs	Adds validation tests for `ZstandardCompressionOptions`.
src/libraries/System.IO.Compression/tests/Zstandard/CompressionStreamUnitTests.Zstandard.cs	Adds `ZstandardStream` coverage integrated with existing stream test base.
src/libraries/System.IO.Compression/tests/System.IO.Compression.Tests.csproj	Integrates Zstandard test sources conditionally (excluding browser/WASI).
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardUtils.cs	Adds shared internal helpers for Zstandard implementation.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.cs	Adds platform attributes on `ZstandardStream`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.Decompress.cs	Adds decompression-side stream implementation under the consolidated assembly.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.Compress.cs	Adds compression-side stream implementation under the consolidated assembly.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardEncoder.cs	Adds platform attributes on `ZstandardEncoder`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardDictionary.cs	Adds platform attributes on `ZstandardDictionary`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardDecoder.cs	Adds platform attributes on `ZstandardDecoder`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardCompressionOptions.cs	Adds platform attributes on `ZstandardCompressionOptions`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/Zstandard.PlatformNotSupported.cs	Adds browser/WASI stubs throwing `PlatformNotSupportedException`.
src/libraries/System.IO.Compression/src/System.IO.Compression.csproj	Multi-target integration for Zstandard sources + stubs under `System.IO.Compression`.
src/libraries/System.IO.Compression/src/Resources/Strings.resx	Merges Zstandard resource strings into `System.IO.Compression` resources.
src/libraries/System.IO.Compression/ref/System.IO.Compression.cs	Adds Zstandard APIs to the `System.IO.Compression` reference surface with platform attributes.
src/libraries/System.IO.Compression/README.md	Updates README to reflect Zstandard support in `System.IO.Compression`.
src/libraries/System.IO.Compression/Directory.Build.props	Removes BOM/normalizes file header.
src/libraries/System.IO.Compression.Zstandard/tests/System.IO.Compression.Zstandard.Tests.csproj	Deletes old Zstandard test project (now integrated into `System.IO.Compression` tests).
src/libraries/System.IO.Compression.Zstandard/src/System.IO.Compression.Zstandard.csproj	Deletes old Zstandard implementation project (now merged into `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/src/Resources/Strings.resx	Deletes old resource file (strings moved to `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/ref/System.IO.Compression.Zstandard.csproj	Deletes old ref project.
src/libraries/System.IO.Compression.Zstandard/ref/System.IO.Compression.Zstandard.cs	Deletes old ref surface file (moved into `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/System.IO.Compression.Zstandard.slnx	Deletes old solution for the removed library.
src/libraries/System.IO.Compression.Zstandard/README.md	Deletes old library README (functionality now documented under `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/Directory.Build.props	Deletes old build props (no longer needed after consolidation).
src/libraries/NetCoreAppLibrary.props	Removes `System.IO.Compression.Zstandard` from the NetCoreApp library list.

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 23 out of 31 changed files in this pull request and generated 1 comment.

iremyux

LGTM

….Compression (dotnet#124634) There is no real benefit from having the APIs in separate assembly because: - the Managed code size is rather small - it P/Invokes System.IO.Compression.Native just like System.IO.Compression managed assembly does - It would lead to circular dependency if we decide to implement dotnet#123532 --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

rzikm · 2026-02-20T10:42:55Z

There is no real benefit from having the APIs in separate assembly because:

the Managed code size is rather small
it P/Invokes System.IO.Compression.Native just like System.IO.Compression managed assembly does
It would lead to circular dependency if we decide to implement Support Zstandard compression in ZipArchives #123532

….Compression Move Zstandard compression/decompression APIs from the separate System.IO.Compression.Zstandard assembly into the main System.IO.Compression assembly for better organization. Changes: - Move source files to src/System/IO/Compression/Zstandard/ subdirectory - Move test files to tests/Zstandard/ subdirectory - Add PNSE stubs for browser/wasi platforms - Update ref API with [UnsupportedOSPlatform] attributes - Merge resource strings into System.IO.Compression Strings.resx - Remove System.IO.Compression.Zstandard project reference from System.Net.Http - Remove System.IO.Compression.Zstandard from NetCoreAppLibrary.props and sfx.slnx - Delete the old System.IO.Compression.Zstandard directory Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

dotnet-policy-service · 2026-02-20T10:44:08Z

Tagging subscribers to this area: @karelz, @dotnet/area-system-io-compression
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

This PR consolidates Zstandard compression APIs into the main System.IO.Compression library, removing the separate System.IO.Compression.Zstandard assembly and updating build/test infrastructure accordingly.

Changes:

Move Zstandard implementation and tests under System.IO.Compression (including ref API surface updates).
Add browser/WASI PlatformNotSupportedException stubs while keeping full implementations on Windows/Unix TFMs.
Remove the old System.IO.Compression.Zstandard project artifacts and references (solutions, props, project references).

Reviewed changes

Copilot reviewed 23 out of 31 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/libraries/sfx.slnx	Removes `System.IO.Compression.Zstandard` ref project from the libraries solution.
src/libraries/System.Net.Http/src/System.Net.Http.csproj	Drops project reference to the removed `System.IO.Compression.Zstandard` project.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardTestUtils.cs	Adds shared helpers for Zstandard tests in the consolidated test project.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardEncoderDecoderTests.cs	Adds encoder/decoder coverage to `System.IO.Compression` tests.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardDictionaryTests.cs	Adds dictionary creation/training tests under `System.IO.Compression`.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardCompressionOptionsTests.cs	Adds validation tests for `ZstandardCompressionOptions`.
src/libraries/System.IO.Compression/tests/Zstandard/CompressionStreamUnitTests.Zstandard.cs	Adds `ZstandardStream` coverage integrated with existing stream test base.
src/libraries/System.IO.Compression/tests/System.IO.Compression.Tests.csproj	Integrates Zstandard test sources conditionally (excluding browser/WASI).
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardUtils.cs	Adds shared internal helpers for Zstandard implementation.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.cs	Adds platform attributes on `ZstandardStream`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.Decompress.cs	Adds decompression-side stream implementation under the consolidated assembly.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.Compress.cs	Adds compression-side stream implementation under the consolidated assembly.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardEncoder.cs	Adds platform attributes on `ZstandardEncoder`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardDictionary.cs	Adds platform attributes on `ZstandardDictionary`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardDecoder.cs	Adds platform attributes on `ZstandardDecoder`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardCompressionOptions.cs	Adds platform attributes on `ZstandardCompressionOptions`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/Zstandard.PlatformNotSupported.cs	Adds browser/WASI stubs throwing `PlatformNotSupportedException`.
src/libraries/System.IO.Compression/src/System.IO.Compression.csproj	Multi-target integration for Zstandard sources + stubs under `System.IO.Compression`.
src/libraries/System.IO.Compression/src/Resources/Strings.resx	Merges Zstandard resource strings into `System.IO.Compression` resources.
src/libraries/System.IO.Compression/ref/System.IO.Compression.cs	Adds Zstandard APIs to the `System.IO.Compression` reference surface with platform attributes.
src/libraries/System.IO.Compression/README.md	Updates README to reflect Zstandard support in `System.IO.Compression`.
src/libraries/System.IO.Compression/Directory.Build.props	Removes BOM/normalizes file header.
src/libraries/System.IO.Compression.Zstandard/tests/System.IO.Compression.Zstandard.Tests.csproj	Deletes old Zstandard test project (now integrated into `System.IO.Compression` tests).
src/libraries/System.IO.Compression.Zstandard/src/System.IO.Compression.Zstandard.csproj	Deletes old Zstandard implementation project (now merged into `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/src/Resources/Strings.resx	Deletes old resource file (strings moved to `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/ref/System.IO.Compression.Zstandard.csproj	Deletes old ref project.
src/libraries/System.IO.Compression.Zstandard/ref/System.IO.Compression.Zstandard.cs	Deletes old ref surface file (moved into `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/System.IO.Compression.Zstandard.slnx	Deletes old solution for the removed library.
src/libraries/System.IO.Compression.Zstandard/README.md	Deletes old library README (functionality now documented under `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/Directory.Build.props	Deletes old build props (no longer needed after consolidation).
src/libraries/NetCoreAppLibrary.props	Removes `System.IO.Compression.Zstandard` from the NetCoreApp library list.

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 23 out of 31 changed files in this pull request and generated 1 comment.

iremyux

LGTM

….Compression (dotnet#124634) There is no real benefit from having the APIs in separate assembly because: - the Managed code size is rather small - it P/Invokes System.IO.Compression.Native just like System.IO.Compression managed assembly does - It would lead to circular dependency if we decide to implement dotnet#123532 --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

rzikm · 2026-02-20T10:42:55Z

There is no real benefit from having the APIs in separate assembly because:

the Managed code size is rather small
it P/Invokes System.IO.Compression.Native just like System.IO.Compression managed assembly does
It would lead to circular dependency if we decide to implement Support Zstandard compression in ZipArchives #123532

….Compression Move Zstandard compression/decompression APIs from the separate System.IO.Compression.Zstandard assembly into the main System.IO.Compression assembly for better organization. Changes: - Move source files to src/System/IO/Compression/Zstandard/ subdirectory - Move test files to tests/Zstandard/ subdirectory - Add PNSE stubs for browser/wasi platforms - Update ref API with [UnsupportedOSPlatform] attributes - Merge resource strings into System.IO.Compression Strings.resx - Remove System.IO.Compression.Zstandard project reference from System.Net.Http - Remove System.IO.Compression.Zstandard from NetCoreAppLibrary.props and sfx.slnx - Delete the old System.IO.Compression.Zstandard directory Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

dotnet-policy-service · 2026-02-20T10:44:08Z

Tagging subscribers to this area: @karelz, @dotnet/area-system-io-compression
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

This PR consolidates Zstandard compression APIs into the main System.IO.Compression library, removing the separate System.IO.Compression.Zstandard assembly and updating build/test infrastructure accordingly.

Changes:

Move Zstandard implementation and tests under System.IO.Compression (including ref API surface updates).
Add browser/WASI PlatformNotSupportedException stubs while keeping full implementations on Windows/Unix TFMs.
Remove the old System.IO.Compression.Zstandard project artifacts and references (solutions, props, project references).

Reviewed changes

Copilot reviewed 23 out of 31 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/libraries/sfx.slnx	Removes `System.IO.Compression.Zstandard` ref project from the libraries solution.
src/libraries/System.Net.Http/src/System.Net.Http.csproj	Drops project reference to the removed `System.IO.Compression.Zstandard` project.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardTestUtils.cs	Adds shared helpers for Zstandard tests in the consolidated test project.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardEncoderDecoderTests.cs	Adds encoder/decoder coverage to `System.IO.Compression` tests.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardDictionaryTests.cs	Adds dictionary creation/training tests under `System.IO.Compression`.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardCompressionOptionsTests.cs	Adds validation tests for `ZstandardCompressionOptions`.
src/libraries/System.IO.Compression/tests/Zstandard/CompressionStreamUnitTests.Zstandard.cs	Adds `ZstandardStream` coverage integrated with existing stream test base.
src/libraries/System.IO.Compression/tests/System.IO.Compression.Tests.csproj	Integrates Zstandard test sources conditionally (excluding browser/WASI).
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardUtils.cs	Adds shared internal helpers for Zstandard implementation.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.cs	Adds platform attributes on `ZstandardStream`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.Decompress.cs	Adds decompression-side stream implementation under the consolidated assembly.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.Compress.cs	Adds compression-side stream implementation under the consolidated assembly.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardEncoder.cs	Adds platform attributes on `ZstandardEncoder`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardDictionary.cs	Adds platform attributes on `ZstandardDictionary`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardDecoder.cs	Adds platform attributes on `ZstandardDecoder`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardCompressionOptions.cs	Adds platform attributes on `ZstandardCompressionOptions`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/Zstandard.PlatformNotSupported.cs	Adds browser/WASI stubs throwing `PlatformNotSupportedException`.
src/libraries/System.IO.Compression/src/System.IO.Compression.csproj	Multi-target integration for Zstandard sources + stubs under `System.IO.Compression`.
src/libraries/System.IO.Compression/src/Resources/Strings.resx	Merges Zstandard resource strings into `System.IO.Compression` resources.
src/libraries/System.IO.Compression/ref/System.IO.Compression.cs	Adds Zstandard APIs to the `System.IO.Compression` reference surface with platform attributes.
src/libraries/System.IO.Compression/README.md	Updates README to reflect Zstandard support in `System.IO.Compression`.
src/libraries/System.IO.Compression/Directory.Build.props	Removes BOM/normalizes file header.
src/libraries/System.IO.Compression.Zstandard/tests/System.IO.Compression.Zstandard.Tests.csproj	Deletes old Zstandard test project (now integrated into `System.IO.Compression` tests).
src/libraries/System.IO.Compression.Zstandard/src/System.IO.Compression.Zstandard.csproj	Deletes old Zstandard implementation project (now merged into `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/src/Resources/Strings.resx	Deletes old resource file (strings moved to `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/ref/System.IO.Compression.Zstandard.csproj	Deletes old ref project.
src/libraries/System.IO.Compression.Zstandard/ref/System.IO.Compression.Zstandard.cs	Deletes old ref surface file (moved into `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/System.IO.Compression.Zstandard.slnx	Deletes old solution for the removed library.
src/libraries/System.IO.Compression.Zstandard/README.md	Deletes old library README (functionality now documented under `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/Directory.Build.props	Deletes old build props (no longer needed after consolidation).
src/libraries/NetCoreAppLibrary.props	Removes `System.IO.Compression.Zstandard` from the NetCoreApp library list.

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 23 out of 31 changed files in this pull request and generated 1 comment.

iremyux

LGTM

….Compression (dotnet#124634) There is no real benefit from having the APIs in separate assembly because: - the Managed code size is rather small - it P/Invokes System.IO.Compression.Native just like System.IO.Compression managed assembly does - It would lead to circular dependency if we decide to implement dotnet#123532 --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

rzikm · 2026-02-20T10:42:55Z

There is no real benefit from having the APIs in separate assembly because:

the Managed code size is rather small
it P/Invokes System.IO.Compression.Native just like System.IO.Compression managed assembly does
It would lead to circular dependency if we decide to implement Support Zstandard compression in ZipArchives #123532

….Compression Move Zstandard compression/decompression APIs from the separate System.IO.Compression.Zstandard assembly into the main System.IO.Compression assembly for better organization. Changes: - Move source files to src/System/IO/Compression/Zstandard/ subdirectory - Move test files to tests/Zstandard/ subdirectory - Add PNSE stubs for browser/wasi platforms - Update ref API with [UnsupportedOSPlatform] attributes - Merge resource strings into System.IO.Compression Strings.resx - Remove System.IO.Compression.Zstandard project reference from System.Net.Http - Remove System.IO.Compression.Zstandard from NetCoreAppLibrary.props and sfx.slnx - Delete the old System.IO.Compression.Zstandard directory Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

dotnet-policy-service · 2026-02-20T10:44:08Z

Tagging subscribers to this area: @karelz, @dotnet/area-system-io-compression
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

This PR consolidates Zstandard compression APIs into the main System.IO.Compression library, removing the separate System.IO.Compression.Zstandard assembly and updating build/test infrastructure accordingly.

Changes:

Move Zstandard implementation and tests under System.IO.Compression (including ref API surface updates).
Add browser/WASI PlatformNotSupportedException stubs while keeping full implementations on Windows/Unix TFMs.
Remove the old System.IO.Compression.Zstandard project artifacts and references (solutions, props, project references).

Reviewed changes

Copilot reviewed 23 out of 31 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/libraries/sfx.slnx	Removes `System.IO.Compression.Zstandard` ref project from the libraries solution.
src/libraries/System.Net.Http/src/System.Net.Http.csproj	Drops project reference to the removed `System.IO.Compression.Zstandard` project.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardTestUtils.cs	Adds shared helpers for Zstandard tests in the consolidated test project.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardEncoderDecoderTests.cs	Adds encoder/decoder coverage to `System.IO.Compression` tests.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardDictionaryTests.cs	Adds dictionary creation/training tests under `System.IO.Compression`.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardCompressionOptionsTests.cs	Adds validation tests for `ZstandardCompressionOptions`.
src/libraries/System.IO.Compression/tests/Zstandard/CompressionStreamUnitTests.Zstandard.cs	Adds `ZstandardStream` coverage integrated with existing stream test base.
src/libraries/System.IO.Compression/tests/System.IO.Compression.Tests.csproj	Integrates Zstandard test sources conditionally (excluding browser/WASI).
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardUtils.cs	Adds shared internal helpers for Zstandard implementation.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.cs	Adds platform attributes on `ZstandardStream`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.Decompress.cs	Adds decompression-side stream implementation under the consolidated assembly.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.Compress.cs	Adds compression-side stream implementation under the consolidated assembly.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardEncoder.cs	Adds platform attributes on `ZstandardEncoder`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardDictionary.cs	Adds platform attributes on `ZstandardDictionary`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardDecoder.cs	Adds platform attributes on `ZstandardDecoder`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardCompressionOptions.cs	Adds platform attributes on `ZstandardCompressionOptions`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/Zstandard.PlatformNotSupported.cs	Adds browser/WASI stubs throwing `PlatformNotSupportedException`.
src/libraries/System.IO.Compression/src/System.IO.Compression.csproj	Multi-target integration for Zstandard sources + stubs under `System.IO.Compression`.
src/libraries/System.IO.Compression/src/Resources/Strings.resx	Merges Zstandard resource strings into `System.IO.Compression` resources.
src/libraries/System.IO.Compression/ref/System.IO.Compression.cs	Adds Zstandard APIs to the `System.IO.Compression` reference surface with platform attributes.
src/libraries/System.IO.Compression/README.md	Updates README to reflect Zstandard support in `System.IO.Compression`.
src/libraries/System.IO.Compression/Directory.Build.props	Removes BOM/normalizes file header.
src/libraries/System.IO.Compression.Zstandard/tests/System.IO.Compression.Zstandard.Tests.csproj	Deletes old Zstandard test project (now integrated into `System.IO.Compression` tests).
src/libraries/System.IO.Compression.Zstandard/src/System.IO.Compression.Zstandard.csproj	Deletes old Zstandard implementation project (now merged into `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/src/Resources/Strings.resx	Deletes old resource file (strings moved to `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/ref/System.IO.Compression.Zstandard.csproj	Deletes old ref project.
src/libraries/System.IO.Compression.Zstandard/ref/System.IO.Compression.Zstandard.cs	Deletes old ref surface file (moved into `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/System.IO.Compression.Zstandard.slnx	Deletes old solution for the removed library.
src/libraries/System.IO.Compression.Zstandard/README.md	Deletes old library README (functionality now documented under `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/Directory.Build.props	Deletes old build props (no longer needed after consolidation).
src/libraries/NetCoreAppLibrary.props	Removes `System.IO.Compression.Zstandard` from the NetCoreApp library list.

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 23 out of 31 changed files in this pull request and generated 1 comment.

iremyux

LGTM

….Compression (dotnet#124634) There is no real benefit from having the APIs in separate assembly because: - the Managed code size is rather small - it P/Invokes System.IO.Compression.Native just like System.IO.Compression managed assembly does - It would lead to circular dependency if we decide to implement dotnet#123532 --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

rzikm · 2026-02-20T10:42:55Z

There is no real benefit from having the APIs in separate assembly because:

the Managed code size is rather small
it P/Invokes System.IO.Compression.Native just like System.IO.Compression managed assembly does
It would lead to circular dependency if we decide to implement Support Zstandard compression in ZipArchives #123532

….Compression Move Zstandard compression/decompression APIs from the separate System.IO.Compression.Zstandard assembly into the main System.IO.Compression assembly for better organization. Changes: - Move source files to src/System/IO/Compression/Zstandard/ subdirectory - Move test files to tests/Zstandard/ subdirectory - Add PNSE stubs for browser/wasi platforms - Update ref API with [UnsupportedOSPlatform] attributes - Merge resource strings into System.IO.Compression Strings.resx - Remove System.IO.Compression.Zstandard project reference from System.Net.Http - Remove System.IO.Compression.Zstandard from NetCoreAppLibrary.props and sfx.slnx - Delete the old System.IO.Compression.Zstandard directory Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

dotnet-policy-service · 2026-02-20T10:44:08Z

Tagging subscribers to this area: @karelz, @dotnet/area-system-io-compression
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

This PR consolidates Zstandard compression APIs into the main System.IO.Compression library, removing the separate System.IO.Compression.Zstandard assembly and updating build/test infrastructure accordingly.

Changes:

Move Zstandard implementation and tests under System.IO.Compression (including ref API surface updates).
Add browser/WASI PlatformNotSupportedException stubs while keeping full implementations on Windows/Unix TFMs.
Remove the old System.IO.Compression.Zstandard project artifacts and references (solutions, props, project references).

Reviewed changes

Copilot reviewed 23 out of 31 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/libraries/sfx.slnx	Removes `System.IO.Compression.Zstandard` ref project from the libraries solution.
src/libraries/System.Net.Http/src/System.Net.Http.csproj	Drops project reference to the removed `System.IO.Compression.Zstandard` project.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardTestUtils.cs	Adds shared helpers for Zstandard tests in the consolidated test project.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardEncoderDecoderTests.cs	Adds encoder/decoder coverage to `System.IO.Compression` tests.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardDictionaryTests.cs	Adds dictionary creation/training tests under `System.IO.Compression`.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardCompressionOptionsTests.cs	Adds validation tests for `ZstandardCompressionOptions`.
src/libraries/System.IO.Compression/tests/Zstandard/CompressionStreamUnitTests.Zstandard.cs	Adds `ZstandardStream` coverage integrated with existing stream test base.
src/libraries/System.IO.Compression/tests/System.IO.Compression.Tests.csproj	Integrates Zstandard test sources conditionally (excluding browser/WASI).
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardUtils.cs	Adds shared internal helpers for Zstandard implementation.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.cs	Adds platform attributes on `ZstandardStream`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.Decompress.cs	Adds decompression-side stream implementation under the consolidated assembly.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.Compress.cs	Adds compression-side stream implementation under the consolidated assembly.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardEncoder.cs	Adds platform attributes on `ZstandardEncoder`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardDictionary.cs	Adds platform attributes on `ZstandardDictionary`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardDecoder.cs	Adds platform attributes on `ZstandardDecoder`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardCompressionOptions.cs	Adds platform attributes on `ZstandardCompressionOptions`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/Zstandard.PlatformNotSupported.cs	Adds browser/WASI stubs throwing `PlatformNotSupportedException`.
src/libraries/System.IO.Compression/src/System.IO.Compression.csproj	Multi-target integration for Zstandard sources + stubs under `System.IO.Compression`.
src/libraries/System.IO.Compression/src/Resources/Strings.resx	Merges Zstandard resource strings into `System.IO.Compression` resources.
src/libraries/System.IO.Compression/ref/System.IO.Compression.cs	Adds Zstandard APIs to the `System.IO.Compression` reference surface with platform attributes.
src/libraries/System.IO.Compression/README.md	Updates README to reflect Zstandard support in `System.IO.Compression`.
src/libraries/System.IO.Compression/Directory.Build.props	Removes BOM/normalizes file header.
src/libraries/System.IO.Compression.Zstandard/tests/System.IO.Compression.Zstandard.Tests.csproj	Deletes old Zstandard test project (now integrated into `System.IO.Compression` tests).
src/libraries/System.IO.Compression.Zstandard/src/System.IO.Compression.Zstandard.csproj	Deletes old Zstandard implementation project (now merged into `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/src/Resources/Strings.resx	Deletes old resource file (strings moved to `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/ref/System.IO.Compression.Zstandard.csproj	Deletes old ref project.
src/libraries/System.IO.Compression.Zstandard/ref/System.IO.Compression.Zstandard.cs	Deletes old ref surface file (moved into `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/System.IO.Compression.Zstandard.slnx	Deletes old solution for the removed library.
src/libraries/System.IO.Compression.Zstandard/README.md	Deletes old library README (functionality now documented under `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/Directory.Build.props	Deletes old build props (no longer needed after consolidation).
src/libraries/NetCoreAppLibrary.props	Removes `System.IO.Compression.Zstandard` from the NetCoreApp library list.

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 23 out of 31 changed files in this pull request and generated 1 comment.

iremyux

LGTM

….Compression (dotnet#124634) There is no real benefit from having the APIs in separate assembly because: - the Managed code size is rather small - it P/Invokes System.IO.Compression.Native just like System.IO.Compression managed assembly does - It would lead to circular dependency if we decide to implement dotnet#123532 --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

rzikm · 2026-02-20T10:42:55Z

There is no real benefit from having the APIs in separate assembly because:

the Managed code size is rather small
it P/Invokes System.IO.Compression.Native just like System.IO.Compression managed assembly does
It would lead to circular dependency if we decide to implement Support Zstandard compression in ZipArchives #123532

….Compression Move Zstandard compression/decompression APIs from the separate System.IO.Compression.Zstandard assembly into the main System.IO.Compression assembly for better organization. Changes: - Move source files to src/System/IO/Compression/Zstandard/ subdirectory - Move test files to tests/Zstandard/ subdirectory - Add PNSE stubs for browser/wasi platforms - Update ref API with [UnsupportedOSPlatform] attributes - Merge resource strings into System.IO.Compression Strings.resx - Remove System.IO.Compression.Zstandard project reference from System.Net.Http - Remove System.IO.Compression.Zstandard from NetCoreAppLibrary.props and sfx.slnx - Delete the old System.IO.Compression.Zstandard directory Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

dotnet-policy-service · 2026-02-20T10:44:08Z

Tagging subscribers to this area: @karelz, @dotnet/area-system-io-compression
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

This PR consolidates Zstandard compression APIs into the main System.IO.Compression library, removing the separate System.IO.Compression.Zstandard assembly and updating build/test infrastructure accordingly.

Changes:

Move Zstandard implementation and tests under System.IO.Compression (including ref API surface updates).
Add browser/WASI PlatformNotSupportedException stubs while keeping full implementations on Windows/Unix TFMs.
Remove the old System.IO.Compression.Zstandard project artifacts and references (solutions, props, project references).

Reviewed changes

Copilot reviewed 23 out of 31 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/libraries/sfx.slnx	Removes `System.IO.Compression.Zstandard` ref project from the libraries solution.
src/libraries/System.Net.Http/src/System.Net.Http.csproj	Drops project reference to the removed `System.IO.Compression.Zstandard` project.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardTestUtils.cs	Adds shared helpers for Zstandard tests in the consolidated test project.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardEncoderDecoderTests.cs	Adds encoder/decoder coverage to `System.IO.Compression` tests.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardDictionaryTests.cs	Adds dictionary creation/training tests under `System.IO.Compression`.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardCompressionOptionsTests.cs	Adds validation tests for `ZstandardCompressionOptions`.
src/libraries/System.IO.Compression/tests/Zstandard/CompressionStreamUnitTests.Zstandard.cs	Adds `ZstandardStream` coverage integrated with existing stream test base.
src/libraries/System.IO.Compression/tests/System.IO.Compression.Tests.csproj	Integrates Zstandard test sources conditionally (excluding browser/WASI).
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardUtils.cs	Adds shared internal helpers for Zstandard implementation.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.cs	Adds platform attributes on `ZstandardStream`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.Decompress.cs	Adds decompression-side stream implementation under the consolidated assembly.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.Compress.cs	Adds compression-side stream implementation under the consolidated assembly.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardEncoder.cs	Adds platform attributes on `ZstandardEncoder`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardDictionary.cs	Adds platform attributes on `ZstandardDictionary`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardDecoder.cs	Adds platform attributes on `ZstandardDecoder`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardCompressionOptions.cs	Adds platform attributes on `ZstandardCompressionOptions`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/Zstandard.PlatformNotSupported.cs	Adds browser/WASI stubs throwing `PlatformNotSupportedException`.
src/libraries/System.IO.Compression/src/System.IO.Compression.csproj	Multi-target integration for Zstandard sources + stubs under `System.IO.Compression`.
src/libraries/System.IO.Compression/src/Resources/Strings.resx	Merges Zstandard resource strings into `System.IO.Compression` resources.
src/libraries/System.IO.Compression/ref/System.IO.Compression.cs	Adds Zstandard APIs to the `System.IO.Compression` reference surface with platform attributes.
src/libraries/System.IO.Compression/README.md	Updates README to reflect Zstandard support in `System.IO.Compression`.
src/libraries/System.IO.Compression/Directory.Build.props	Removes BOM/normalizes file header.
src/libraries/System.IO.Compression.Zstandard/tests/System.IO.Compression.Zstandard.Tests.csproj	Deletes old Zstandard test project (now integrated into `System.IO.Compression` tests).
src/libraries/System.IO.Compression.Zstandard/src/System.IO.Compression.Zstandard.csproj	Deletes old Zstandard implementation project (now merged into `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/src/Resources/Strings.resx	Deletes old resource file (strings moved to `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/ref/System.IO.Compression.Zstandard.csproj	Deletes old ref project.
src/libraries/System.IO.Compression.Zstandard/ref/System.IO.Compression.Zstandard.cs	Deletes old ref surface file (moved into `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/System.IO.Compression.Zstandard.slnx	Deletes old solution for the removed library.
src/libraries/System.IO.Compression.Zstandard/README.md	Deletes old library README (functionality now documented under `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/Directory.Build.props	Deletes old build props (no longer needed after consolidation).
src/libraries/NetCoreAppLibrary.props	Removes `System.IO.Compression.Zstandard` from the NetCoreApp library list.

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 23 out of 31 changed files in this pull request and generated 1 comment.

iremyux

LGTM

….Compression (dotnet#124634) There is no real benefit from having the APIs in separate assembly because: - the Managed code size is rather small - it P/Invokes System.IO.Compression.Native just like System.IO.Compression managed assembly does - It would lead to circular dependency if we decide to implement dotnet#123532 --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

rzikm · 2026-02-20T10:42:55Z

There is no real benefit from having the APIs in separate assembly because:

the Managed code size is rather small
it P/Invokes System.IO.Compression.Native just like System.IO.Compression managed assembly does
It would lead to circular dependency if we decide to implement Support Zstandard compression in ZipArchives #123532

….Compression Move Zstandard compression/decompression APIs from the separate System.IO.Compression.Zstandard assembly into the main System.IO.Compression assembly for better organization. Changes: - Move source files to src/System/IO/Compression/Zstandard/ subdirectory - Move test files to tests/Zstandard/ subdirectory - Add PNSE stubs for browser/wasi platforms - Update ref API with [UnsupportedOSPlatform] attributes - Merge resource strings into System.IO.Compression Strings.resx - Remove System.IO.Compression.Zstandard project reference from System.Net.Http - Remove System.IO.Compression.Zstandard from NetCoreAppLibrary.props and sfx.slnx - Delete the old System.IO.Compression.Zstandard directory Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

dotnet-policy-service · 2026-02-20T10:44:08Z

Tagging subscribers to this area: @karelz, @dotnet/area-system-io-compression
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

This PR consolidates Zstandard compression APIs into the main System.IO.Compression library, removing the separate System.IO.Compression.Zstandard assembly and updating build/test infrastructure accordingly.

Changes:

Move Zstandard implementation and tests under System.IO.Compression (including ref API surface updates).
Add browser/WASI PlatformNotSupportedException stubs while keeping full implementations on Windows/Unix TFMs.
Remove the old System.IO.Compression.Zstandard project artifacts and references (solutions, props, project references).

Reviewed changes

Copilot reviewed 23 out of 31 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/libraries/sfx.slnx	Removes `System.IO.Compression.Zstandard` ref project from the libraries solution.
src/libraries/System.Net.Http/src/System.Net.Http.csproj	Drops project reference to the removed `System.IO.Compression.Zstandard` project.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardTestUtils.cs	Adds shared helpers for Zstandard tests in the consolidated test project.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardEncoderDecoderTests.cs	Adds encoder/decoder coverage to `System.IO.Compression` tests.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardDictionaryTests.cs	Adds dictionary creation/training tests under `System.IO.Compression`.
src/libraries/System.IO.Compression/tests/Zstandard/ZstandardCompressionOptionsTests.cs	Adds validation tests for `ZstandardCompressionOptions`.
src/libraries/System.IO.Compression/tests/Zstandard/CompressionStreamUnitTests.Zstandard.cs	Adds `ZstandardStream` coverage integrated with existing stream test base.
src/libraries/System.IO.Compression/tests/System.IO.Compression.Tests.csproj	Integrates Zstandard test sources conditionally (excluding browser/WASI).
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardUtils.cs	Adds shared internal helpers for Zstandard implementation.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.cs	Adds platform attributes on `ZstandardStream`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.Decompress.cs	Adds decompression-side stream implementation under the consolidated assembly.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardStream.Compress.cs	Adds compression-side stream implementation under the consolidated assembly.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardEncoder.cs	Adds platform attributes on `ZstandardEncoder`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardDictionary.cs	Adds platform attributes on `ZstandardDictionary`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardDecoder.cs	Adds platform attributes on `ZstandardDecoder`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/ZstandardCompressionOptions.cs	Adds platform attributes on `ZstandardCompressionOptions`.
src/libraries/System.IO.Compression/src/System/IO/Compression/Zstandard/Zstandard.PlatformNotSupported.cs	Adds browser/WASI stubs throwing `PlatformNotSupportedException`.
src/libraries/System.IO.Compression/src/System.IO.Compression.csproj	Multi-target integration for Zstandard sources + stubs under `System.IO.Compression`.
src/libraries/System.IO.Compression/src/Resources/Strings.resx	Merges Zstandard resource strings into `System.IO.Compression` resources.
src/libraries/System.IO.Compression/ref/System.IO.Compression.cs	Adds Zstandard APIs to the `System.IO.Compression` reference surface with platform attributes.
src/libraries/System.IO.Compression/README.md	Updates README to reflect Zstandard support in `System.IO.Compression`.
src/libraries/System.IO.Compression/Directory.Build.props	Removes BOM/normalizes file header.
src/libraries/System.IO.Compression.Zstandard/tests/System.IO.Compression.Zstandard.Tests.csproj	Deletes old Zstandard test project (now integrated into `System.IO.Compression` tests).
src/libraries/System.IO.Compression.Zstandard/src/System.IO.Compression.Zstandard.csproj	Deletes old Zstandard implementation project (now merged into `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/src/Resources/Strings.resx	Deletes old resource file (strings moved to `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/ref/System.IO.Compression.Zstandard.csproj	Deletes old ref project.
src/libraries/System.IO.Compression.Zstandard/ref/System.IO.Compression.Zstandard.cs	Deletes old ref surface file (moved into `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/System.IO.Compression.Zstandard.slnx	Deletes old solution for the removed library.
src/libraries/System.IO.Compression.Zstandard/README.md	Deletes old library README (functionality now documented under `System.IO.Compression`).
src/libraries/System.IO.Compression.Zstandard/Directory.Build.props	Deletes old build props (no longer needed after consolidation).
src/libraries/NetCoreAppLibrary.props	Removes `System.IO.Compression.Zstandard` from the NetCoreApp library list.

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iremyux

LGTM

….Compression (dotnet#124634) There is no real benefit from having the APIs in separate assembly because: - the Managed code size is rather small - it P/Invokes System.IO.Compression.Native just like System.IO.Compression managed assembly does - It would lead to circular dependency if we decide to implement dotnet#123532 --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

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