Expose `OperatingSystem.IsApplePlatform` publicly and Clean up watchOS by makazeu · Pull Request #135475 · dotnet/runtime

makazeu · 2026-10-09T07:29:23Z

As discussed in #113262 and the video, we're good to make this helper exposed publicly in OperatingSystem.

This pull request refactors platform checks throughout the codebase to consolidate Apple-related OS checks into a single method, OperatingSystem.IsApplePlatform(). It also removes support for watchOS, updating both implementation and tests accordingly. This streamlines platform detection logic, reduces duplication, and clarifies current platform support.

Platform detection refactoring:

Introduced and made public OperatingSystem.IsApplePlatform(), replacing multiple checks for individual Apple platforms (IsMacOS, IsIOS, IsTvOS, IsMacCatalyst) in both product and test code. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]
Updated comments and documentation to reflect the consolidated Apple platform detection, and removed references to watchOS where appropriate. [1] [2] [3] [4]

watchOS deprecation/removal:

Removed support for watchOS in platform detection APIs (IsWatchOS now always returns false and is documented as unsupported), in version checks, and in native code. [1] [2] [3] [4]

Test updates:

Updated and simplified tests to use the new IsApplePlatform() method and removed watchOS from test cases and assertions. [1] [2] [3]

These changes improve maintainability by centralizing Apple platform logic and clarify that watchOS is no longer a supported target.

dotnet#113262

azure-pipelines · 2026-10-09T07:30:06Z

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dotnet-policy-service · 2026-10-09T07:30:32Z

Tagging subscribers to this area: @dotnet/area-system-runtime
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Added a HashSet for all Apple platform names and updated tests to verify Apple platform detection.

Add Ref and tests for public IsApplePlatform API

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

vcsjones · 2026-10-09T13:51:22Z

I assume we are going to need a corresponding pull request from someone for the compatibility analyzer? I don't know if the analyzer will handle this without changes. https://github.com/dotnet/dotnet/blob/4fd6fbb479abbacd43b32fdc0ef6f68414cc028d/src/sdk/src/Microsoft.CodeAnalysis.NetAnalyzers/src/Microsoft.CodeAnalysis.NetAnalyzers/Microsoft.NetCore.Analyzers/InteropServices/PlatformCompatibilityAnalyzer.cs

…Pal.Unix.cs Co-authored-by: Jan Kotas <jkotas@microsoft.com>

makazeu · 2026-10-09T20:19:40Z

watchOS will NOT be added to IsApplePlatform since modern .NET doesn't support it, and all previous isWatchOS checks had been removed. #117653

jkotas · 2026-10-09T20:59:31Z

Revert isWatchOS change

I think it was a fine change - for consistency.

We do not currently build and test for watch OS, but the code for it still there.

jkotas · 2026-10-09T21:03:22Z

all previous isWatchOS checks had been removed

It looks odd when one place in the same file assumes that watchOS does not exist, but other place treats it as a thing.

makazeu · 2026-10-10T01:13:34Z

all previous isWatchOS checks had been removed

It looks odd when one place in the same file assumes that watchOS does not exist, but other place treats it as a thing.

Yeah, exactly. That’s why I initially added watchOS.

However, after thinking about @vcsjones 's comment on the compatibility analyzer, I decided to remove watchOS for now.

Let's assume the platform compatibility analyzer supports IsApplePlatform() and checks all five platforms, including watchOS:
Consider an API annotated as supported on the other 4 platforms. Even if the call site is guarded by OperatingSystem.IsApplePlatform(), the analyzer would still report a compatibility issue.

I wanted to avoid this situation. After all, new APIs won't explicitly include [SupportedOSPlatform("watchos")] anymore. @jkotas What do you think?

makazeu · 2026-10-10T01:27:14Z

I assume we are going to need a corresponding pull request from someone for the compatibility analyzer? I don't know if the analyzer will handle this without changes. https://github.com/dotnet/dotnet/blob/4fd6fbb479abbacd43b32fdc0ef6f68414cc028d/src/sdk/src/Microsoft.CodeAnalysis.NetAnalyzers/src/Microsoft.CodeAnalysis.NetAnalyzers/Microsoft.NetCore.Analyzers/InteropServices/PlatformCompatibilityAnalyzer.cs

Sure, I'll follow up on this, thanks!

jkotas · 2026-10-10T06:19:17Z

Let's assume the platform compatibility analyzer supports IsApplePlatform() and checks all five platforms, including watchOS

I do not think that this has any impact on platform compatibility analyzer user experience.

The platform compatibility analyzer only checks compatibly for platforms specified via <SupportedPlatform> item group. This set is Windows/macOS/Linux by default - https://github.com/dotnet/sdk/blob/main/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.SupportedPlatforms.props . It means that you can be calling APIs that are unsupported on SomeOtherOS and it won't warn by default. You have to opt-in your project into checking compatibility with SomeOtherOS.

makazeu · 2026-10-10T08:11:05Z

Let's assume the platform compatibility analyzer supports IsApplePlatform() and checks all five platforms, including watchOS

I do not think that this has any impact on platform compatibility analyzer user experience.

The platform compatibility analyzer only checks compatibly for platforms specified via <SupportedPlatform> item group. This set is Windows/macOS/Linux by default - https://github.com/dotnet/sdk/blob/main/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.SupportedPlatforms.props . It means that you can be calling APIs that are unsupported on SomeOtherOS and it won't warn by default. You have to opt-in your project into checking compatibility with SomeOtherOS.

@jkotas Thanks for the clear explanation! I hadn’t realized that the analyzer’s platform checks are scoped by <SupportedPlatform>— I learned something new here.

Given that, how would you prefer to handle watchOS in IsApplePlatform()? Should we keep it excluded for consistency with #117653, or include it for consistency with the remaining watchOS detection code? Including it would effectively reintroduce watchOS checks at the call sites converted to IsApplePlatform(), partially undoing that earlier cleanup.

jkotas · 2026-10-10T18:57:01Z

how would you prefer to handle watchOS in IsApplePlatform()?

Option 1: Add TARGET_WATCHOS to the ifdef in IsApplePlatform

Option 2: Delete TARGET_WATCHOS ifdef in IsWatchOS() and replace with a comment that says watchOS is no longer supported. Also, delete watchOS references in src\libraries\System.Private.CoreLib\src\System\Runtime\InteropServices\RuntimeInformation.Unix.cs, src\libraries\System.Runtime\tests\System.Runtime.Extensions.Tests\System\OperatingSystemTests.cs, src\native\eventpipe\ep-event-source.c, src\native\libs\System.Native\pal_time.c, src\native\libs\System.Security.Cryptography.Native.Apple\pal_ssl.c.

Pick the one you like better - either one is fine with me.

makazeu · 2026-10-11T03:22:21Z

Pick the one you like better - either one is fine with me.

I prefer option 2 - to do a deeper cleanup of watchOS.

Copilot

🟡 Changes recommended

IsApplePlatform lacks platform-guard annotations in both its implementation and reference declaration, so the compatibility analyzer cannot infer Apple-platform exclusions and consumers may still receive CA1416 warnings.

2 open issues

What changed in this PR

This PR exposes OperatingSystem.IsApplePlatform() publicly, as proposed in #113262, and adopts it across library code and tests. It also removes obsolete watchOS detection paths while retaining the public watchOS helpers as always-false checks.

Changes:

Adds the public Apple-platform helper and test assertions.
Consolidates repeated Apple OS checks across file-system and networking code.
Removes watchOS-specific detection branches and updates related documentation.

File	Description
src/native/libs/System.Security.Cryptography.Native.Apple/pal_ssl.c	Removes watchOS from a comment.
src/native/libs/System.Native/pal_time.c	Removes watchOS from a fallback comment.
src/native/eventpipe/ep-event-source.c	Removes watchOS event-source identification.
src/libraries/System.Runtime/tests/System.Runtime.Extensions.Tests/System/OperatingSystemTests.cs	Adds Apple-platform assertions and removes watchOS cases.
src/libraries/System.Runtime/ref/System.Runtime.cs	Declares the new public helper.
src/libraries/System.Private.CoreLib/src/System/Runtime/InteropServices/RuntimeInformation.Unix.cs	Removes the watchOS description branch.
src/libraries/System.Private.CoreLib/src/System/OperatingSystem.cs	Exposes the helper and makes watchOS checks always false.
src/libraries/System.Net.Sockets/src/System/Net/Sockets/SocketPal.Unix.cs	Simplifies the Apple-specific select workaround check.
src/libraries/System.Net.Quic/src/System/Net/Quic/Interop/msquic.cs	Consolidates Apple socket-address layout checks.
src/libraries/System.Net.Ping/tests/FunctionalTests/PingTest.cs	Simplifies ping-utility platform detection.
src/libraries/System.Net.NetworkInformation/tests/FunctionalTests/IPGlobalPropertiesTest.cs	Consolidates Apple exclusions for IPv6 statistics.
src/libraries/System.IO.MemoryMappedFiles/tests/MemoryMappedViewStream.Tests.cs	Simplifies Apple executable-memory permission handling.
src/libraries/System.IO.MemoryMappedFiles/tests/MemoryMappedViewAccessor.Tests.cs	Simplifies Apple executable-memory permission handling.
src/libraries/Common/src/System/IO/PathInternal.CaseSensitivity.cs	Uses the helper for file-system case-sensitivity detection.

_{Review effort: Balanced}

+        [NonVersionable]
+        public static bool IsApplePlatform() =>


        public static bool IsMacCatalystVersionAtLeast(int major, int minor = 0, int build = 0) { throw null; }
        public static bool IsMacOS() { throw null; }
        public static bool IsMacOSVersionAtLeast(int major, int minor = 0, int build = 0) { throw null; }
+        public static bool IsApplePlatform() { throw null; }


jkotas · 2026-11-04T01:37:04Z

@makazeu Could you please address copilot feedback?

Expose IsApplePlatforms publicly in OperatingSystem

9706bca

dotnet#113262

github-actions Bot added the area-System.Runtime label Oct 9, 2026

dotnet-policy-service Bot added the community-contribution Indicates that the PR has been added by a community member label Oct 9, 2026

makazeu and others added 4 commits October 9, 2026 17:07

Add IsApplePlatform method to System.Runtime ref

cc2c424

Add Apple platform names and update OS tests

9bd99b7

Added a HashSet for all Apple platform names and updated tests to verify Apple platform detection.

Add Ref and tests for public IsApplePlatform API

fdcba7a

Add Ref and tests for public IsApplePlatform API

Simplify Apple platform assertion

155f9df

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

makazeu changed the title ~~Expose IsApplePlatforms publicly in OperatingSystem~~ Expose IsApplePlatform publicly in OperatingSystem Oct 9, 2026

Add TARGET_WATCHOS to IsApplePlatform check

4ffd821

jkotas reviewed Oct 9, 2026

View reviewed changes

Comment thread src/libraries/System.Private.CoreLib/src/System/OperatingSystem.cs Resolved

Use public IsApplePlatform API

8d32b32

jkotas reviewed Oct 9, 2026

View reviewed changes

Comment thread src/libraries/System.Net.Sockets/src/System/Net/Sockets/SocketPal.Unix.cs Resolved

makazeu and others added 3 commits October 10, 2026 01:26

Update src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket…

94e7476

…Pal.Unix.cs Co-authored-by: Jan Kotas <jkotas@microsoft.com>

Merge branch 'main' into patch-1

edc9853

fix CI pipelines

850c8eb

Revert isWatchOS change

7f9917f

build-analysis Bot mentioned this pull request Oct 10, 2026

[ci-scan] Test failure: System.Net.Security.Tests.SslStream tests fail with "The remote certificate was rejected ..." #135096

Closed

makazeu mentioned this pull request Oct 10, 2026

Recognize IsApplePlatform as a four-platform OS guard dotnet/sdk#56576

Draft

makazeu changed the title ~~Expose IsApplePlatform publicly in OperatingSystem~~ Expose OperatingSystem.IsApplePlatform publicly and Clean up watchOS Oct 11, 2026

Remove watchOS support from OperatingSystem and related files

032eb2b

makazeu requested review from lateralusX, mdh1418 and noahfalk as code owners October 11, 2026 03:28

This was referenced Oct 11, 2026

SslStreamTlsResumeTests.DifferentEncryptionPolicy_NoResume failing #133418

Closed

Runtime_133587 SIGSEGV in mono #133910

Open

[ci-scan] Build break: unable to pull Helix prerequisite image #134176

Open

Merge branch 'main' into patch-1

1e85f75

This was referenced Nov 2, 2026

Test failure: IdsConversionsWithRegionTest America/Vancouver America/Los_Angeles mismatch #136758

Open

[browser] Wasm.Build.Tests timeout - Timed out after 10s waiting for 'WASM EXIT' #116697

Open

jkotas requested a balanced review from Copilot November 4, 2026 01:12

Merge branch 'main' into patch-1

a0cb7be

Copilot started reviewing on behalf of jkotas November 4, 2026 01:12

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Copilot AI reviewed Nov 4, 2026

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