Annotate MS.CA and MS.CA.C# for trimming by agocke · Pull Request #66519 · dotnet/roslyn

agocke · 2023-01-22T23:40:59Z

Brief description of trimming analysis: when trimming an application, the libraries should be annotated to be trim-compatible or, if that's not possible, to alert the user which APIs will not be compatible with trimming.

Almost all of MS.CA and MS.CA.CSharp are already trimming compatible, it is only native PDB writing which has problems (because it uses built-in COM support, which is basically reflection). The native PDB writing could eventually be moved to use COM wrappers and be made trim-compatible, but right now I've simply marked the APIs incompatible. There are still plenty of useful APIs for consumers, including all the syntax and binding APIs, that don't use PDB emit.

agocke · 2023-02-13T18:09:35Z

@dotnet/roslyn-compiler for review

agocke · 2023-02-13T18:09:52Z

@jaredpar

src/Compilers/CSharp/Portable/CSharpFileSystemExtensions.cs

src/Compilers/CSharp/Portable/Microsoft.CodeAnalysis.CSharp.csproj

src/Compilers/Core/CodeAnalysisTest/ObjectSerializationTests.cs

src/Compilers/Core/Portable/CodeAnalysisEventSource.cs

jaredpar · 2023-03-14T18:03:21Z

src/Compilers/Core/Portable/Diagnostic/LocalizableResourceString.cs

-        static LocalizableResourceString()
-        {
-            ObjectBinder.RegisterTypeReader(typeof(LocalizableResourceString), reader => new LocalizableResourceString(reader));
-        }


Need an explanation on why this was removed.

This is fundamentally untrimmable, but the only usage I found was in tests.

Are we sure this isn't used for diagnostics being serialized across processes?

I tried and couldn't find a place where it was used. The integration tests are also passing. I'm not sure how else to verify this.

src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerAssemblyLoader.cs

src/Compilers/Core/Portable/InternalUtilities/FatalError.cs

src/Compilers/Core/Portable/InternalUtilities/ReflectionUtilities.cs

src/Compilers/Core/Portable/InternalUtilities/RoslynLazyInitializer.cs

src/Compilers/Core/Portable/InternalUtilities/UICultureUtilities.cs

src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerAssemblyLoader.cs

agocke · 2023-03-15T22:39:11Z

Not sure what's up with roslyn-ci here.

agocke · 2023-03-27T16:26:17Z

Looks like the integration-corehost tests are a bit of a disaster. I'm going to ignore them unless someone has specific suggestions.

agocke · 2023-04-17T18:18:32Z

FYI we're bringing the first version of the COMWrapper source generator online, which will fix the trim issues in Emit, but I'm not going to include that work in this PR.

huoyaoyuan · 2023-04-20T03:39:11Z

src/Compilers/CSharp/Portable/Microsoft.CodeAnalysis.CSharp.csproj

  </PropertyGroup>
+
+  <!-- Enable trimming/AOT compat -->
+  <PropertyGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETCoreApp' AND '$(_TargetFrameworkVersionWithoutV)' &gt;= '6.0'">


$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net6.0')) ?

jcouv · 2023-05-09T19:17:42Z

@agocke What's the next step for this PR? We can mark it as draft if it still needs some work to figure out (not quite ready for another look yet), to make room in our review queue.

agocke · 2023-05-09T19:30:58Z

Jared's review is stale. This is ready. Next steps are on your side.

Sergio0694 · 2023-05-11T10:00:04Z

src/Compilers/Core/Portable/InternalUtilities/DynamicallyAccessedMembersAttribute.cs

+    AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.Method |
+    AttributeTargets.Class | AttributeTargets.Interface | AttributeTargets.Struct,
+    Inherited = false)]
+internal sealed class DynamicallyAccessedMembersAttribute : Attribute


Not sure whether Roslyn has special rules/policies for NuGet dependencies, but would it make sense to leverage PolySharp here rather than manually adding polyfills with ifdefs on new targets? PolySharp handles that automatically, and if size is a concern you can also configure it to only ever polyfill the exact types you need, rather than all available ones. It would also make it simpler to extend this in the future when/if more polyfills were needed.

For instance, for the changes in this PR you'd just need:

<ItemGroup> <PackageReference Include="PolySharp" Version="1.13.1" PrivateAssets="all" /> </ItemGroup> <PropertyGroup> <PolySharpIncludeGeneratedTypes> System.Diagnostics.CodeAnalysis.DynamicallyAccessedMembersAttribute; System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes; System.Diagnostics.CodeAnalysis.RequiresUnreferencedCodeAttribute; System.Diagnostics.CodeAnalysis.UnconditionalSuppressMessageAttribute; </PolySharpIncludeGeneratedTypes> </PropertyGroup>

teo-tsirpanis · 2025-08-24T22:37:54Z

src/Compilers/Core/Portable/InternalUtilities/TrimWarningMessages.cs

+internal static class TrimWarningMessages
+{
+    internal const string AnalyzerReflectionLoadMessage = "Loading analyzers via reflection is not supported when trimming.";
+    internal const string NativePdbsNotSupported = "Native PDBs use built-in COM, which is not supported when trimming.";


This might be fixed with dotnet/symreader#340.

Fixed link: dotnet/symreader#340
Should we file a roslyn issue to revisit the annotations once that PR is merged?

tmat · 2025-08-25T16:04:42Z

src/Compilers/Core/Portable/InternalUtilities/UnconditionalSuppressMessageAttribute.cs

+/// <see cref="ConditionalAttribute"/>. So it is always preserved in the compiled assembly.
+/// </remarks>
+[AttributeUsage(AttributeTargets.All, Inherited = false, AllowMultiple = true)]
+internal sealed class UnconditionalSuppressMessageAttribute : Attribute


Should use TypeForwardedTo on NET like so: https://github.com/dotnet/roslyn/blob/main/src/Dependencies/Contracts/IsExternalInit.cs

I don't think it's necessary here. IsExternalInit needs type forwarding to maintain binary compatibility because it gets used in modreqs, while tooling matches this attribute by name (99% sure).

But as seen in https://patch-diff.githubusercontent.com/raw/dotnet/roslyn/pull/66519.diff, this file is unused, so maybe we can just delete it.

Even if it's not necessary here I prefer we follow a single pattern.

jcouv · 2025-08-25T20:04:02Z

src/Compilers/Core/Portable/CodeAnalysisEventSource.cs

 // See the LICENSE file in the project root for more information.

 using System;
+using System.Diagnostics.CodeAnalysis;


Can be reverted?

jcouv · 2025-08-25T20:23:55Z

src/Compilers/Core/CodeAnalysisTest/ObjectSerializationTests.cs

-            TestRoundTripType(typeof(int));
-            TestRoundTripType(typeof(string));
-            TestRoundTripType(typeof(ObjectSerializationTests));
-        }


@agocke General question: could you share a bit about the overall flow/story? In particular, when/where do the messages in the annotations surface to users?
Also, what is the approach you use to find all the methods that need to be instrumented? (how do we know the annotations are complete?)

jcouv · 2025-09-22T14:48:40Z

@agocke Marked as draft since looks stale. Please un-draft and ping when ready for another look. Thanks

Sergio0694 · 2026-02-26T01:01:21Z

Just for context we hit this in CsWinRT 3.0 as well, as we are shipping a new build tool as a Native AOT binary, which uses the Roslyn APIs to compile Windows Runtime projections from sources at publish time. For now we've had to just suppress all trimming warnings (see here), which seems to still work, but isn't ideal. We'd love to see this merged 🙂

ghost added the Area-Compilers label Jan 22, 2023

agocke mentioned this pull request Jan 26, 2023

Update BCL versions to .NET 7 #66561

Merged

agocke changed the title ~~Add net6.0 MS.CA and MS.CA.C# build and annotate for trimming~~ Annotate MS.CA and MS.CA.C# for trimming Feb 12, 2023

agocke force-pushed the make-trimmable branch 2 times, most recently from 96947e8 to d10d229 Compare February 12, 2023 03:45

agocke added 2 commits February 12, 2023 19:18

Make MS.CA trimmable

46be428

Make MS.CA.C# trimmable

c78e67c

agocke force-pushed the make-trimmable branch from 73a219e to c78e67c Compare February 13, 2023 03:27

Fix formatting

11f1db1

agocke marked this pull request as ready for review February 13, 2023 18:09

agocke requested a review from a team as a code owner February 13, 2023 18:09

agocke mentioned this pull request Mar 13, 2023

Roslyn analyzer assembly loading with NativeAOT dotnet/runtime#83355

Closed

jaredpar requested changes Mar 14, 2023

View reviewed changes

Add polyfills

5538f07

agocke requested a review from a team as a code owner March 14, 2023 19:22

agocke added 2 commits March 14, 2023 12:23

Missed a file

37ca83b

Add linked polyfill for integration test

0ed8f9c

agocke requested a review from a team as a code owner March 14, 2023 19:46

Also fix up ResultProvider

2195ecf

jaredpar reviewed Mar 14, 2023

View reviewed changes

src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerAssemblyLoader.cs Show resolved Hide resolved

Also fixup ResultProvider.Utilities

4a2ed9d

jaredpar self-assigned this Mar 14, 2023

agocke added 3 commits March 14, 2023 13:47

Add remaining trim warning messages to unified file

8892a71

Add TrimWarningMessages file to projects

3952abd

Fix up a few more project files

05fb4e9

jaredpar closed this Mar 16, 2023

jaredpar reopened this Mar 16, 2023

agocke added 2 commits March 22, 2023 09:50

Add Message property to RequiresUnreferencedCodeAttribute

77c5064

Fix formatting

01841d2

build-analysis bot mentioned this pull request Mar 24, 2023

NuGet failing with Response status code does not indicate success: 503 (Service Unavailable) dotnet/arcade#11723

Open

5 tasks

agocke added 2 commits March 24, 2023 10:44

Set trimmability for >= 6.0

d551ae7

Forgot '&'

c487f27

huoyaoyuan reviewed Apr 20, 2023

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agocke requested a review from jaredpar May 9, 2023 19:31

jcouv mentioned this pull request May 10, 2023

Microsoft.CodeAnalysis.* trimming support #68154

Open

Sergio0694 reviewed May 11, 2023

View reviewed changes

jaredpar added this to the Backlog milestone Jul 18, 2023

agocke added 3 commits August 14, 2023 20:38

Merge remote-tracking branch 'upstream/main' into make-trimmable

a99eb95

Update projects with new AOT properties

756642f

Remove eventsource suppression

5c19759

baronfel mentioned this pull request Aug 21, 2025

Enable the dotnet CLI to be shipped as a Native AOT application dotnet/sdk#49667

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59 tasks

teo-tsirpanis reviewed Aug 24, 2025

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tmat reviewed Aug 25, 2025

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jcouv reviewed Aug 25, 2025

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jaredpar modified the milestones: Backlog, Next Next Aug 25, 2025

jcouv marked this pull request as draft September 22, 2025 14:48

jcouv self-assigned this Sep 22, 2025

phil-allen-msft modified the milestones: Next Next, 18.4 Oct 10, 2025

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