fix(mocks): eliminate trim/AOT warnings on Native AOT publish

[thomhurst]

Fixes #7027

Problem

Publishing a project that uses TUnit.Mocks with PublishAot=true made ILC report IL2026, IL2055, IL3050 and IL2069 from TUnit.Mocks, even for basic mocks. With TreatWarningsAsErrors, publish failed. #pragma warning disable only silences the Roslyn analyzer. ILC does not see pragmas.

Mock.Of<IRepository<int>>() also closed the open generated mock through MakeGenericType. Native AOT cannot always do this for value-type arguments, so this could fail at runtime.

Fix

• MockEngine: the opt-in DefaultValueProvider lookup was duplicated in 17 pragma-wrapped blocks. It is now one TryGetCustomDefault<TReturn> helper with [UnconditionalSuppressMessage]. Behaviour is unchanged.
• OpenGenericFactoryDescriptor: added [param: DynamicallyAccessedMembers]. This fixes IL2069.
• Closed generic registrations (generator): for each closed generic interface named at a Mock.Of<T>() / MockRepository.Of<T>() call site or in [assembly: GenerateMock(typeof(T))], the generator emits MockRegistry.RegisterFactory<IRepository<int>>(...). This calls the generated CreateAutoMock<int> directly, so no reflection is needed and the instantiation is rooted for AOT. Type arguments that are not accessible (private or protected nested types) or are file-local are skipped. Results are deduplicated and sorted, and the step stays cached when only call-site locations change.
• Runtime fallback: MakeGenericType is now used only when the type is known only at runtime. Its suppressions have justifications. On Native AOT, a missing instantiation throws a NotSupportedException that names the type and the fix.
• Docs: added a "Native AOT and Generic Interfaces" section to writing-tests/mocking/advanced.md.

No public API change.

Regression tests

• TUnit.Mocks.Aot.Tests (new): covers everyday mock usage (the issue repro, generic mocks with value and reference type arguments, async members, events, strict mode, verification, repository). The project uses TreatWarningsAsErrors and TrimmerSingleWarn=false. The Linux AOT pipeline job publishes it for net8.0, net9.0 and net10.0, then runs the native executable. Any trim/AOT warning from TUnit.Mocks fails CI. I checked that the guard works: without the helper's suppression, ILC fails with error IL2026 and error IL3050.
• TUnit.Mocks.Tests/Issue7027Tests.cs: value-type, struct, multi-argument and nested generic mocks; strict mode; repository; rejection of constructor arguments. One test checks that each factory comes from generated code and not the reflection fallback. Another tests the runtime-only fallback. These tests also run as Native AOT in CI.
• Issue7027DefaultValueProviderTests: covers provider value, null, wrong type, CanProvide == false, and per-type checks. They run on every engine arity (typed 1–8, untyped 0 and 9+) and on both plain and auto-mock return paths.
• TUnit.Mocks.SourceGenerator.Tests/Issue7027Tests.cs: 22 tests covering registration contents, ordering, deduplication, MockRepository, [GenerateMock], skipped cases (open, private, file-local, multi-interface, .Mock() extension), nested and global-namespace types, constraints, compile checks, and incrementality. The snapshot changes are intentional: generic-interface snapshots now include the registration file.

Verification

• Native AOT publish of the issue repro and of TUnit.Mocks.Aot.Tests (win-x64, ILC run with the platform linker skipped): no IL warnings on net8.0, net9.0 or net10.0. Before the fix, the issue repro gave IL2026 ×2, IL3050 ×4, IL2055 ×2 and IL2069 ×2.
• TUnit.Mocks.Tests (net10.0): 1354/1354 passed. TUnit.Mocks.SourceGenerator.Tests: 192/192 passed. TUnit.Mocks.Aot.Tests (JIT): 11/11 passed.
• I could not run the native executables locally because this machine has no MSVC linker. The Linux CI job runs them.

Summary by CodeRabbit

• New Features

  • Generated mocks now support closed generic interfaces under Native AOT when their types are known at compile time, including interfaces with value-type arguments.

• Improvements

  • Custom default values are handled consistently across mock methods with different numbers of arguments; existing auto-mock, strict-mock, and loose-mock fallback behavior remains unchanged.
  • When Native AOT cannot create a generic mock at runtime, the error identifies the unsupported type and explains that it must be registered ahead of time.

• Documentation

  • Added guidance on Native AOT support and limitations for generic mocks and default-value providers.
  • Clarified that TUnit.Mocks requires C# 14 and recommends T.Mock() for mock creation, with alternatives for specific cases.

[chatgpt-codex-connector]

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📝 Walkthrough

Walkthrough

The source generator now emits factories for eligible closed generic interfaces. Runtime mock handling centralizes custom-default lookup and updates closed-generic creation for Native AOT. New tests, pipeline coverage, and documentation address these changes.

Changes

Closed generic mocks and Native AOT

Layer / File(s)	Summary
Discover and emit closed-generic factories src/TUnit.Mocks.SourceGenerator/*, tests/TUnit.Mocks.SourceGenerator.Tests/*	The generator discovers eligible closed generic interfaces from Mock.Of<T>(), MockRepository.Of<T>(), and [assembly: GenerateMock]. It resolves registrations and emits module-initialized factories. Regression tests and snapshots cover supported and excluded cases.
Runtime factory and custom-default handling src/TUnit.Mocks/MockRegistry.cs, src/TUnit.Mocks/MockEngine.cs, src/TUnit.Mocks/MockEngine.Typed*.cs, tests/TUnit.Mocks.Tests/Issue7027Tests.cs	The registry adds constructor-preservation annotations and translates selected closed-generic creation failures into a descriptive Native AOT exception. The mock engine centralizes custom-default lookup, and typed handlers use the helper for arities one through eight. Regression tests cover generic registrations and custom-default behavior.
AOT tests and publish pipeline tests/TUnit.Mocks.Aot.Tests/*, tools/TUnit.Pipeline/Modules/*MockTestsAOTModule.cs, TUnit*.slnx, .gitignore	A new Native AOT test project covers mock behavior and generic interfaces. The pipeline publishes and runs both mock test projects for three target frameworks. The solution files include the new project.
Mocking examples and Native AOT guidance README.md, docs/docs/migration/mocking/*, docs/docs/writing-tests/mocking/*	The documentation updates mock-creation examples and C# 14 guidance. It adds guidance for closed generic mocks, runtime-created generic types, and default-value providers under Native AOT.

Priority: ➖ Normal

Estimated code review effort: 4 (Complex) | ~45 minutes

Change: Bug fix · Severity of issue fixed: Medium

Sequence Diagram(s)

sequenceDiagram
  participant TestCode
  participant MockTypeDiscovery
  participant ClosedGenericRegistrationBuilder
  participant MockGenerator
  participant ModuleInitializer
  participant MockRegistry
  TestCode->>MockTypeDiscovery: Declare closed generic mock usage
  MockTypeDiscovery->>MockGenerator: Provide eligible registration
  MockGenerator->>ClosedGenericRegistrationBuilder: Resolve registration against mock models
  ClosedGenericRegistrationBuilder->>MockGenerator: Return factory emissions
  MockGenerator->>ModuleInitializer: Emit factory registration
  ModuleInitializer->>MockRegistry: Register closed-generic factory
  TestCode->>MockRegistry: Create registered closed-generic mock

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Merge Risk: 🔵 Low · up to 19f45

The change adds Native AOT support for generic interface mocks. The Native AOT docs may overstate which closed generic types are registered ahead of time. This is a minor documentation risk and should not block merge.

Pre-merge checks | 4 | 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 8.57% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 140 functions across 14 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the primary change: removing trim and Native AOT warnings from mock-related publishing.
Linked Issues check		Issue #7027 requires warning-free Native AOT publishing for basic and generic-interface mocks. MockEngine<T> now centralizes default-provider calls in TryGetCustomDefault<TReturn> with linker and …
Out of Scope Changes check		The changes remain connected to issue #7027. Runtime refactoring, source-generator registrations, fallback diagnostics, documentation, regression tests, solution entries, and AOT pipeline updates supp…

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[github-actions]

Review

Looks good. The change is behaviour-preserving and fixes the root cause. ILC ignores #pragma, but it honours [UnconditionalSuppressMessage].

• TryGetCustomDefault<TReturn>: it matches the removed inline logic. A provider value of the wrong type falls through, null returns default, and a matching type returns the value. Replacing 17 duplicated pragma blocks with one helper is a clear maintainability gain, and the suppression now lives in one place.
• OpenGenericFactoryDescriptor: adding [param: DynamicallyAccessedMembers] next to [property: ...] is the correct fix for IL2069. Annotating only the property leaves the constructor parameters unannotated, so the warning follows.
• CreateClosedGenericMock: moving to method-level attributes with justifications is fine.

Minor, non-blocking points:

1. The CreateClosedGenericMock suppressions are broad because they cover the whole method. If the method grows, new unsafe calls will be silenced too. Keeping the body minimal, or noting this in a comment, would help.
2. The generic helper may be instantiated once per TReturn for value types. This only adds a small amount of code, and it is outweighed by removing the inlined blocks.
3. A regression guard would help: a CI step that publishes a tiny AOT app with TreatWarningsAsErrors and TrimmerSingleWarn=false, to stop pragma-only suppressions from coming back. The PR's manual verification is good, but nothing enforces it.

I didn't build or run anything here. This review is based on the diff and the PR description. Approving in spirit.

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Reviewed commit: e2f8237ae0

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[greptile-apps]

Confidence Score: 5/5

[Medium impact] The PR appears safe to merge; no new blocking issue was found.

Summary

The PR adds generated factories for closed generic interface mocks, replaces pragma-based warning suppression with attributes, and adds Native AOT publish coverage.

• Closed generic interfaces named in source use generated mock factories.
• Custom default providers no longer add trim and AOT warnings to ordinary mocks.
• Runtime-only generic mocks now explain when Native AOT lacks a compiled type.
• A dedicated mock test app publishes and runs as a native AOT program.
• Mocking docs now explain the preferred syntax and Native AOT paths.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["Closed generic mock requested"] --> B{"Generated closed factory registered?"}
    B -->|Yes| C["Call generated CreateAutoMock directly"]
    B -->|No| D["Use reflection fallback"]
    D --> E{"Instantiation available?"}
    E -->|Yes| F["Return mock"]
    E -->|No, under Native AOT| G["Throw error with repair guidance"]

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_{Reviews (6) · Last reviewed commit: "refactor(mocks): keep fallback suppressi..." · Reviewed by Greptile}

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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @src/TUnit.Mocks/MockRegistry.cs:
- Line 151: Preserve Native AOT behavior for value-type generic mocks created
through CreateClosedGenericMock. Add a Native AOT regression test; if these
mocks are supported, root the required closed generated implementation and
wrapper instantiations or avoid the reflection-based MakeGenericType path. If
they are unsupported, reject value-type generic mocks and remove the IL3050
suppression rather than treating RegisterOpenGenericFactory as sufficient
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[thomhurst]

Responding to the github-actions review:

1. Broad method-level suppressions: the reflection now lives in a small CreateClosedGenericMockCore method. The outer method only checks arguments and turns Native AOT failures into a clear error. Each method has a justification for its suppressions.
2. Regression guard: added in de3d819. The new tests/TUnit.Mocks.Aot.Tests project sets TreatWarningsAsErrors and TrimmerSingleWarn=false. The Linux AOT pipeline job publishes it with -p:Aot=true for net8.0, net9.0 and net10.0, then runs the native executable. To check that the guard works, I removed the [UnconditionalSuppressMessage] from TryGetCustomDefault and published again: ILC failed with error IL2026 and error IL3050.

[github-actions]

Review of #7029 (Native AOT warnings in TUnit.Mocks)

I read the diff and did not run the tests or an AOT publish. The code-review skill failed to start, so this is a manual review. I found nothing blocking.

What looks good

• Replacing the 17 pragma-wrapped blocks with one TryGetCustomDefault<TReturn> helper is the right fix. It uses [UnconditionalSuppressMessage], which ILC honours and #pragma does not. Behaviour is unchanged.
• Registering closed factories from the generator means Mock.Of<IRepository<int>>() no longer goes through MakeGenericType. That is the proper fix for value-type arguments under AOT. Reflection is left as a fallback only for types the generator can't see.
• The incremental pipeline is built carefully: the models are equatable, the emissions are sorted with an ordinal comparer, and tracking names are added so the cached-step behaviour can be tested.
• Skipping inaccessible, file-local and error-type arguments means the generator can't break the user's build. Those cases fall back to reflection.
• The NotSupportedException names the type and the fix. The catch filter !IsDynamicCodeSupported && ex is A or B or C parses correctly, because or is a pattern combinator and binds inside the is.
• The new TUnit.Mocks.Aot.Tests project builds with TreatWarningsAsErrors and is wired into the pipeline. It guards against this regressing, and the docs section helps users.

Suggestions (non-blocking)

1. In TransformGenerateMockAttributeToClosedGenericRegistrations, ForAttributeWithMetadataName uses predicate: static (node, _) => true. That's fine for assembly attributes. A short comment saying so would help, because it reads like a missing filter.
2. The runtime fallback still carries four UnconditionalSuppressMessage attributes. That is correct, but the justification only holds if the open-generic registration annotations stay in place. I'd add a test that fails if the DynamicallyAccessedMembers annotations on OpenGenericFactoryDescriptor are removed, or confirm the AOT test project would catch that.
3. The names in Mock.Of<T>() calls inside user generic helpers, such as Mock.Of<IRepository<T>>() with a runtime T, still hit the fallback. The docs mention GenerateMock, which is good. A generator diagnostic could point users to it, but that can be a follow-up.

Overall this is a solid fix.

[github-actions]

Review of #7029 (Native AOT warnings in TUnit.Mocks)

I read the diff but did not build it or run any tests. The code-review skill failed to run, so this is a manual review.

What's good

• Replacing the 17 pragma-wrapped blocks with one TryGetCustomDefault<TReturn> carrying [UnconditionalSuppressMessage] fixes the real cause. ILC ignores #pragma, and this also removes the duplication.
• Registering closed generics statically through the generator avoids MakeGenericType for value-type arguments, which is the actual runtime AOT hazard. MakeGenericType is kept as a fallback only.
• The generator step is incremental-friendly: results are deduplicated, ordinally sorted, and tracked by name. Inaccessible, file-local and error types are skipped instead of breaking the user's build.
• A new TUnit.Mocks.Aot.Tests project exercises publish with warnings as errors, and the docs section explains the fallback.

Points to consider (non-blocking)

1. Duplicate registrations across assemblies. Each assembly that mentions IRepository<int> emits its own module-initializer RegisterFactory<IRepository<int>>. Please confirm RegisterFactory is last-wins or idempotent and does not throw on a second registration. A small test with two assemblies would settle it.
2. Catch filter readability. when (!IsDynamicCodeSupported && ex is NotSupportedException or MemberAccessException or TypeLoadException) parses as intended, since is A or B or C is a single pattern. Parenthesising the pattern would stop a future reader from misreading the precedence.
3. Suppression justification. The IL3050 and IL2055 suppressions on the fallback rely on NotSupportedException being thrown at runtime. This is reasonable and documented. A generator diagnostic (info or warning) for closed generics that could not be pre-registered, such as file-local type arguments, would make the fallback visible at build time instead of at runtime.
4. Snapshots. Please confirm the generator snapshot tests were re-run and only intentional .verified.txt files changed, with no .received.txt files committed.

The design is sound and I see no blocking issues.

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[thomhurst]

Responding to the latest github-actions reviews (fixes in f83882c):

• Duplicate registrations across assemblies: RegisterFactory<T> assigns with the dictionary indexer (_factories[typeof(T)] = factory), so the last registration wins and nothing throws. Every assembly registers an equivalent factory (the closed CreateAutoMock<...> of the same open mock), so it does not matter which one wins.
• Catch filter readability: the pattern is now in parentheses: ex is (NotSupportedException or MemberAccessException or TypeLoadException).
• predicate: true on the attribute provider: added a comment. It is an assembly-level attribute, so the metadata name is the only filter needed.
• Guard against removing the DynamicallyAccessedMembers annotations: TUnit.Mocks.Aot.Tests mocks generic interfaces, so ILC analyses RegisterOpenGenericFactory and the OpenGenericFactoryDescriptor constructor. Removing the [param:] annotations brings back IL2069, which fails that publish because warnings are errors.
• Snapshots: the generator suite was re-run (194/194 passing). Only intentional .verified.txt files changed, and no .received.txt files are committed.
• Build-time diagnostic for closed generics that can't be pre-registered: good idea, but I'm leaving it for a follow-up. Those cases (private nested or file-local type arguments, types known only at runtime) already get a descriptive NotSupportedException on Native AOT, and the docs explain the fix.

[github-actions]

Review of #7029 (Native AOT warnings in TUnit.Mocks)

I read the diff and the key code paths. I did not build the PR or run its tests.

Overall: the approach looks sound.

• TryGetCustomDefault<TReturn>: replacing the 17 pragma blocks with one attribute-suppressed helper is the right fix, because ILC ignores #pragma. The helper keeps the original behaviour: a typed result returns, a null result gives default, and any other result falls through.
• Closed generic registration in the generator:
  • It registers closed factories ahead of time instead of relying on MakeGenericType. That avoids a runtime reflection failure for value-type arguments.
  • Open type arguments, inaccessible types, file-local types and error types are skipped. Those cases fall back to the runtime path rather than breaking the build.
  • Output is deduplicated and sorted, and the tracking names support incremental-cache tests.
• Runtime fallback: the NotSupportedException naming the type and the fix is much easier to act on than a raw AOT failure.

Suggestions (non-blocking):

1. Check that RegisterFactory called from the [ModuleInitializer] cannot overwrite or conflict with a user's own registration for the same closed type. The ordering is implicit and worth a test.
2. The catch filter ex is (NotSupportedException or MemberAccessException or TypeLoadException) is broad. Make sure it cannot wrap exceptions thrown by user code or a mock constructor.
3. Add generator snapshot tests, with .verified.txt files, for the new ClosedGenericFactories.g.cs output, including the skip cases. The PR description suggests the incremental-cache behaviour is covered, but I did not confirm it.

No blocking issues found. The new TUnit.Mocks.Aot.Tests project is a good regression guard.

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