[linker] Remove Foundation member attributes

[rolfbjarne]

Remove Foundation.RequiredMemberAttribute and Foundation.OptionalMemberAttribute instances unconditionally using the platform assembly's embedded ILLink descriptor.

Add linked-output metadata coverage that verifies both Foundation attributes are removed while System.Runtime.CompilerServices.RequiredMemberAttribute remains unaffected.

🤖 Pull request created by Copilot

[vs-mobiletools-engineering-service2]

✅ API diff for current PR / commit

NET (empty diffs)

• iOS: vsdrops gist ( No breaking changes )
• tvOS: vsdrops gist ( No breaking changes )
• MacCatalyst: vsdrops gist ( No breaking changes )
• macOS: vsdrops gist ( No breaking changes )

✅ API diff vs stable

NET (empty diffs)

• iOS: vsdrops gist ( No breaking changes )
• tvOS: vsdrops gist ( No breaking changes )
• MacCatalyst: vsdrops gist ( No breaking changes )
• macOS: vsdrops gist ( No breaking changes )

ℹ️ Generator diff

Generator Diff: vsdrops (html) vsdrops (raw diff) gist (raw diff) - Please review changes)

Pipeline on Agent
Hash: a34913226a94654f5ad903731980af9fe400cd85 [PR build]

[vs-mobiletools-engineering-service2]

🔥 [CI Build #a349132] Test results 🔥

Test results

❌ Tests failed on VSTS: test results

1 tests crashed, 1 tests failed, 198 tests passed.

Failures

❌ windows tests

1 tests failed, 2 tests passed.

Failed tests

• Remote .NET tests/Xamarin.Tests.DotNetProjectTest.AppWithLibraryWithResourcesReferenceOnRemoteWindows(iOS,"ios-arm64",False): Failed: 'dotnet build' failed with exit code 1

Html Report (VSDrops) Download

❌ xcframework tests

🔥 Failed catastrophically on VSTS: test results - xcframework (no summary found).

Html Report (VSDrops) Download

Successes

✅ assembly-processing: All 1 tests passed. Html Report (VSDrops) Download
✅ cecil: All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (iOS): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (MacCatalyst): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (macOS): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (Multiple platforms): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (tvOS): All 1 tests passed. Html Report (VSDrops) Download
✅ framework: All 2 tests passed. Html Report (VSDrops) Download
✅ fsharp: All 4 tests passed. Html Report (VSDrops) Download
✅ generator: All 5 tests passed. Html Report (VSDrops) Download
✅ interdependent-binding-projects: All 4 tests passed. Html Report (VSDrops) Download
✅ introspection: All 4 tests passed. Html Report (VSDrops) Download
✅ linker (iOS): All 15 tests passed. Html Report (VSDrops) Download
✅ linker (MacCatalyst): All 15 tests passed. Html Report (VSDrops) Download
✅ linker (macOS): All 21 tests passed. Html Report (VSDrops) Download
✅ linker (tvOS): All 15 tests passed. Html Report (VSDrops) Download
✅ monotouch (iOS): All 19 tests passed. Html Report (VSDrops) Download
✅ monotouch (MacCatalyst): All 18 tests passed. Html Report (VSDrops) Download
✅ monotouch (macOS): All 19 tests passed. Html Report (VSDrops) Download
✅ monotouch (tvOS): All 19 tests passed. Html Report (VSDrops) Download
✅ msbuild: All 2 tests passed. Html Report (VSDrops) Download
✅ sharpie: All 1 tests passed. Html Report (VSDrops) Download
✅ xtro: All 1 tests passed. Html Report (VSDrops) Download

macOS tests

✅ Tests on macOS Monterey (12): All 5 tests passed. Html Report (VSDrops) Download
✅ Tests on macOS Ventura (13): All 5 tests passed. Html Report (VSDrops) Download
✅ Tests on macOS Sonoma (14): All 5 tests passed. Html Report (VSDrops) Download
✅ Tests on macOS Sequoia (15): All 5 tests passed. Html Report (VSDrops) Download
✅ Tests on macOS Tahoe (26): All 5 tests passed. Html Report (VSDrops) Download

Linux Build Verification

✅ Linux build succeeded

Pipeline on Agent
Hash: a34913226a94654f5ad903731980af9fe400cd85 [PR build]

[Copilot]

Pull request overview

Removes Foundation.RequiredMemberAttribute and Foundation.OptionalMemberAttribute custom-attribute instances during trimming by extending the platform assembly’s embedded ILLink descriptor, and adds a linked-output unit test to ensure those Foundation attributes are stripped while the compiler’s System.Runtime.CompilerServices.RequiredMemberAttribute remains.

Changes:

• Updated the embedded linker descriptor to remove instances of the two Foundation “member” attributes.
• Added a small iOS test app that applies [Foundation.RequiredMember] / [Foundation.OptionalMember] and also uses a C# required property.
• Added a PublishTrimmedTest that builds the app with full linking and uses Cecil to verify expected attribute removal/preservation in the linked outputs.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
tests/dotnet/UnitTests/PublishTrimmedTest.cs	Adds a new trim/link validation test that inspects linked assemblies for removed/preserved attribute instances.
tests/dotnet/LinkerAttributesTestApp/LinkerAttributesTestApp.csproj	Introduces a minimal iOS test project used by the new trimming test.
tests/dotnet/LinkerAttributesTestApp/AppDelegate.cs	Adds code that emits both Foundation member attributes and the compiler-required-member attribute for verification post-link.
src/ILLink.LinkAttributes.xml.in	Extends the embedded ILLink descriptor to remove instances of Foundation.OptionalMemberAttribute and Foundation.RequiredMemberAttribute.