Add MSTest reflection source generator (issue #1837)

[Evangelink]

Fixes part of #1837.

What

Introduces a new Roslyn IIncrementalGenerator (project MSTest.SourceGeneration, under src/Analyzers/) that discovers [TestClass] types at compile time and emits a [ModuleInitializer] registering a SourceGeneratedReflectionDataProvider for the user's assembly.

It also adds the runtime infrastructure in MSTestAdapter.PlatformServices (folder SourceGeneration/) to swap the IReflectionOperations and IFileOperations services for source-gen-backed implementations once metadata is registered.

This is the first step toward Native AOT support: when the generator runs, MSTest reads test metadata from compile-time-known data instead of doing reflection at runtime. The feature is opt-in — when no metadata is registered, the platform keeps using the existing reflection-based implementations.

Why

Issue #1837 tracks Native AOT support for MSTest. PR #8263 introduced the IReflectionOperations service abstraction as a prerequisite. This PR delivers the next building block by adding the source generator that will populate that abstraction without reflection.

Layout

• Generator (new project): src/Analyzers/MSTest.SourceGeneration/ — ReflectionMetadataGenerator and its emitters/models/helpers, packaged as analyzers/dotnet/cs.
• Runtime hook & shims: src/Adapter/MSTestAdapter.PlatformServices/SourceGeneration/ — ReflectionMetadataHook, SourceGeneratedReflectionDataProvider, CompositeSourceGeneratedReflectionDataProvider, SourceGeneratedReflectionOperations, SourceGeneratedFileOperations, SourceGeneratorToggle.
• Hook surface on PlatformServiceProvider: a single internal SetSourceGeneratedOperations method used by ReflectionMetadataHook to swap providers.
• Removed: the legacy src/Adapter/MSTest.Engine/ project and its unit tests, which the new design replaces. (This is what shows up in the solution-file diff.)
• Unit tests: test/UnitTests/MSTest.SourceGeneration.UnitTests/.
• PublicAPI.Unshipped.txt updated.

Scope (MVP)

• Generator emits a per-assembly [ModuleInitializer] that calls ReflectionMetadataHook.SetMetadata.
• Composite provider supports multiple test assemblies registering concurrently.
• Unit tests cover the happy path ([TestClass] + [TestMethod]), static/abstract classes being skipped, empty-assembly emission, and a Roslyn-compiles-cleanly smoke test.

Known follow-ups (out of scope for this PR)

These are intentionally deferred to keep this PR reviewable:

• Populate the rest of the data bag (AssemblyAttributes, TypeAttributes, TypeProperties, TypeMethodAttributes, TypeConstructorsInvoker, TypeMethodLocations). The MVP only emits the assembly name, type list, and per-type method list.
• [ModuleInitializer] polyfill for netstandard2.0 / older TFM consumers.
• MSBuild gating (opt-in property like EnableMSTestSourceGeneration).
• NuGet packaging of the generator into the MSTest analyzer set.
• Wire up coverage of DataRow / DynamicData / inherited attributes / base-class roll-up.
• AssemblyInitialize / ClassInitialize / TestInitialize lifecycle.

Validation

Built locally with build.cmd -c Debug (0 warnings, 0 errors).

Notes for reviewers

• Public API is intentionally minimal: only ReflectionMetadataHook.SetMetadata and the SourceGeneratedReflectionDataProvider shape are public, because the generated module initializer needs to call them.
• SourceGeneratorToggle uses Interlocked.Exchange to ensure exactly-once swap and to make the toggle race-free if multiple assemblies' module initializers run.
• ReflectionMetadataGenerator skips static and abstract types — they cannot be discovered as test classes.
• IReflectionOperations.GetType(string) delegates straight to the fallback so callers cannot bind to a same-named type from the wrong assembly via the composite TypesByName lookup; the assembly-qualified GetType(Assembly, string) overload is the one that uses the source-generated data.
• Happy to split this into smaller PRs (e.g., runtime infra first, then generator) if that's easier to review.

[Copilot]

Pull request overview

This PR introduces an opt-in MSTest reflection metadata source generator (MSTestAdapter.PlatformServices.SourceGeneration) plus new runtime infrastructure in MSTestAdapter.PlatformServices to swap IReflectionOperations/IFileOperations to source-gen-backed implementations via a generated [ModuleInitializer]. This is intended as an early building block toward NativeAOT support (#1837).

Changes:

• Add a new incremental generator project that discovers [TestClass]/[TestMethod] and emits a module initializer registering metadata.
• Add runtime “source-generated” reflection/file operations and a public hook (ReflectionMetadataHook) for generated code to register metadata.
• Add unit tests for the generator and wire new projects into TestFx.slnx and MSTest.slnf, plus update PublicAPI.Unshipped.txt.

Show a summary per file

File	Description
TestFx.slnx	Adds the new generator project + its unit test project to the full solution.
MSTest.slnf	Adds the new generator project + its unit test project to the MSTest solution filter.
src/Adapter/MSTestAdapter.PlatformServices/PlatformServiceProvider.cs	Adds internal hook to swap IReflectionOperations/IFileOperations.
src/Adapter/MSTestAdapter.PlatformServices/PublicAPI/PublicAPI.Unshipped.txt	Declares new public API surface (ReflectionMetadataHook, SourceGeneratedReflectionDataProvider).
src/Adapter/MSTestAdapter.PlatformServices/SourceGeneration/*.cs	Adds runtime hook + source-gen-backed reflection/file operations + toggle.
src/Adapter/MSTestAdapter.PlatformServices.SourceGeneration/*	Adds generator models/helpers + incremental generator + emitter + banned symbols.
test/UnitTests/MSTestAdapter.PlatformServices.SourceGeneration.UnitTests/*	Adds generator unit tests + test runner program + test project.

Copilot's findings

• Files reviewed: 19/19 changed files
• Comments generated: 14

[Evangelink]

🔍 Build Failure Analysis

Summary — The build failed due to a missing interface method and enforced code style violations across multiple target frameworks.

Root cause 1: Missing interface method SetSourceGeneratedOperations

The code in ReflectionMetadataHook.cs calls SetSourceGeneratedOperations on an IPlatformServiceProvider interface reference, but this method is not declared in the interface — it only exists as an internal method on the concrete PlatformServiceProvider class (line 181).

Affected files / errors

• src/Adapter/MSTestAdapter.PlatformServices/SourceGeneration/ReflectionMetadataHook.cs:37 — CS1061: 'IPlatformServiceProvider' does not contain a definition for 'SetSourceGeneratedOperations' (occurs across net8.0 and net9.0 target frameworks)

Proposed fix

Cast PlatformServiceProvider.Instance to the concrete type before calling the internal method:

-        PlatformServiceProvider.Instance.SetSourceGeneratedOperations(reflectionOperations, fileOperations);
+        ((PlatformServiceProvider)PlatformServiceProvider.Instance).SetSourceGeneratedOperations(reflectionOperations, fileOperations);

Alternative fix (if you want to expose this as part of the interface contract):

Add the method to IPlatformServiceProvider.cs:

     ITestContext GetTestContext(ITestMethod? testMethod, string? testClassFullName, IDictionary<string, object?> properties, IMessageLogger messageLogger, UTF.UnitTestOutcome outcome);
+
+    /// <summary>
+    /// Swaps the cached reflection and file operations with source-generated implementations.
+    /// </summary>
+    void SetSourceGeneratedOperations(IReflectionOperations reflectionOperations, IFileOperations fileOperations);
 }

And change the PlatformServiceProvider implementation from internal to public.

---

Root cause 2: Code style violations (IDE0032 — Use auto property)

Four fields are declared with explicit backing fields but could be converted to auto-properties. The analyzer rule IDE0032 is being enforced as an error.

Affected files / errors

• src/Adapter/MSTestAdapter.PlatformServices/SourceGeneration/SourceGeneratorToggle.cs:13 — error IDE0032: Use auto property
• src/Adapter/MSTestAdapter.PlatformServices/SourceGeneration/SourceGeneratedReflectionOperations.cs:15 — error IDE0032: Use auto property
• src/Adapter/MSTestAdapter.PlatformServices/SourceGeneration/SourceGeneratedFileOperations.cs:16 — error IDE0032: Use auto property

Proposed fix

Convert explicit backing fields to auto-properties. These are readonly fields that are only assigned once in the constructor, so they can use the newer auto-property syntax with initializers.

---

Root cause 3: Code style violations (IDE0046 — Simplify conditional expression)

Three locations have if statements that can be simplified to conditional expressions. The analyzer rule IDE0046 is being enforced as an error.

Affected files / errors

• src/Adapter/MSTestAdapter.PlatformServices/SourceGeneration/SourceGeneratedReflectionOperations.cs:26 — error IDE0046: 'if' statement can be simplified
• src/Adapter/MSTestAdapter.PlatformServices/SourceGeneration/SourceGeneratedReflectionOperations.cs:257 — error IDE0046: 'if' statement can be simplified
• src/Adapter/MSTestAdapter.PlatformServices/SourceGeneration/SourceGeneratedReflectionOperations.cs:291 — error IDE0046: 'if' statement can be simplified

Proposed fix

Simplify if/return patterns to ternary expressions or null-coalescing operators where appropriate.

---

Build overview

• Project: MSTestAdapter.PlatformServices.csproj
• Target frameworks: net8.0, net9.0 (errors occur in both)
• Configuration: Debug
• Exit code: 1 (failure)
• Total unique errors: 7 distinct issues (multiplied across TFMs = 14 total occurrences)

The build failed during the CoreCompile target when compiling the newly added SourceGeneration code.

All MSBuild errors (14 occurrences)

Code	Project	File:Line	Message
CS1061	MSTestAdapter.PlatformServices	ReflectionMetadataHook.cs:37	'IPlatformServiceProvider' does not contain a definition for 'SetSourceGeneratedOperations'... (net8.0)
CS1061	MSTestAdapter.PlatformServices	ReflectionMetadataHook.cs:37	'IPlatformServiceProvider' does not contain a definition for 'SetSourceGeneratedOperations'... (net9.0)
IDE0032	MSTestAdapter.PlatformServices	SourceGeneratorToggle.cs:13	Use auto property (net8.0)
IDE0032	MSTestAdapter.PlatformServices	SourceGeneratorToggle.cs:13	Use auto property (net9.0)
IDE0032	MSTestAdapter.PlatformServices	SourceGeneratedReflectionOperations.cs:15	Use auto property (net8.0)
IDE0032	MSTestAdapter.PlatformServices	SourceGeneratedReflectionOperations.cs:15	Use auto property (net9.0)
IDE0032	MSTestAdapter.PlatformServices	SourceGeneratedFileOperations.cs:16	Use auto property (net8.0)
IDE0032	MSTestAdapter.PlatformServices	SourceGeneratedFileOperations.cs:16	Use auto property (net9.0)
IDE0046	MSTestAdapter.PlatformServices	SourceGeneratedReflectionOperations.cs:26	'if' statement can be simplified (net8.0)
IDE0046	MSTestAdapter.PlatformServices	SourceGeneratedReflectionOperations.cs:26	'if' statement can be simplified (net9.0)
IDE0046	MSTestAdapter.PlatformServices	SourceGeneratedReflectionOperations.cs:257	'if' statement can be simplified (net8.0)
IDE0046	MSTestAdapter.PlatformServices	SourceGeneratedReflectionOperations.cs:257	'if' statement can be simplified (net9.0)
IDE0046	MSTestAdapter.PlatformServices	SourceGeneratedReflectionOperations.cs:291	'if' statement can be simplified (net8.0)
IDE0046	MSTestAdapter.PlatformServices	SourceGeneratedReflectionOperations.cs:291	'if' statement can be simplified (net9.0)

---

_{🤖 Generated by the Build Failure Analysis workflow · commit 6887de2}

Generated by Build Failure Analysis for issue #8586 · ● 1.3M · ◷

[Evangelink]

Generated by Build Failure Analysis for issue #8586 · ● 1.3M

[Copilot]

Copilot's findings

• Files reviewed: 171/172 changed files
• Comments generated: 2