Reduce MSTest source generation startup overhead

[Amaury Levé (Evangelink)]

Summary

• remove generated DataRows and parameter-name descriptors that runtime registration never consumes
• enumerate methods and properties once per test class while preserving exact overload matching and reflection fallback
• pre-size registration dictionaries and pass immutable assembly attributes without a startup copy
• strengthen generator and packaged acceptance coverage for DataRow, DynamicData, overloads, inherited metadata, and compact generated output

Performance

Representative six-class test assembly, 100 warmed process starts:

Metric	Before	After	Change
Median startup	150.41 ms	133.79 ms	-11.0%
Mean startup	159.22 ms	134.18 ms	-15.7%
Registry source	95,900 B	84,188 B	-12.2%
Generated assembly	47,616 B	45,568 B	-4.3%

Validation

• 125 MSTest.SourceGeneration unit tests
• focused packaged acceptance tests on net8.0 and net10.0 (4 cases)
• repository package build with metadata validation

No tracking issue.

[Copilot]

Pull request overview

Reduces reflection-free MSTest source-generation startup overhead while preserving metadata resolution and fallback behavior.

Changes:

• Removes unused DataRow and parameter-name descriptors.
• Reuses reflected member arrays and pre-sizes registration dictionaries.
• Expands generator and packaged acceptance coverage.

Show a summary per file

File	Description
test/UnitTests/MSTest.SourceGeneration.UnitTests/MSTestReflectionMetadataGeneratorTests.cs	Updates generated-output expectations and coverage.
test/IntegrationTests/MSTest.Acceptance.IntegrationTests/SourceGenerationNonAotTests.cs	Validates compact output, overloads, and runtime behavior.
src/Analyzers/MSTest.SourceGeneration/Models/TestClassModel.cs	Removes unused model fields.
src/Analyzers/MSTest.SourceGeneration/Generators/TestClassModelBuilder.cs	Stops constructing unused metadata.
src/Analyzers/MSTest.SourceGeneration/Generators/RuntimeRegistrationEmitter.cs	Optimizes reflection enumeration and collection allocation.
src/Analyzers/MSTest.SourceGeneration/Generators/MetadataRegistryEmitter.cs	Emits a smaller registry and zero-copy assembly attributes.
src/Analyzers/MSTest.SourceGeneration/Generators/DataRowBuilder.cs	Removes obsolete DataRow descriptor generation.
src/Adapter/MSTestAdapter.PlatformServices/SourceGeneration/ReflectionMetadataHook.cs	Clarifies collection ownership and immutability expectations.

Review details

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• Files reviewed: 8/8 changed files
• Comments generated: 0
• Review effort level: Balanced

[github-actions]

🧵 Parallel-safety audit — PR #10545

Parallelization — one row per test assembly audited:

Test assembly	Scope	Workers	Analyzer coverage
MSTest.SourceGeneration.UnitTests	off (no opt-in found: no [assembly: Parallelize], .runsettings, testconfig.json, or MSTestParallelizeScope)	n/a	n/a
MSTest.Acceptance.IntegrationTests	off (no opt-in found for this project)	n/a	n/a

⚠️ Parallelization is OFF for both audited assemblies — this is a readiness checklist, not live bugs. Nothing here fails today.

Findings: A (global-state) 0 · B (paths) 0 · C (declaration) 0 · D (over-serialization) 0 — by severity: Critical 0 · High 0 · Warning 0 · Info 0.

Top actions (by expected value): none — no unsafe call sites found in the changed test regions.

---

Details

The two changed test files are:

• test/UnitTests/MSTest.SourceGeneration.UnitTests/MSTestReflectionMetadataGeneratorTests.cs — changes only update Should().Contain/NotContain assertions on generator output strings (e.g. AssemblyAttributes, DataRowAttribute shape, ResolveMethod/ResolveProperty signatures). No Environment.*, Directory.*, File.*, static-field mutation, [ResourceLock]/[DoNotParallelize] declaration change, or lifecycle-member change is present in the diff.
• test/IntegrationTests/MSTest.Acceptance.IntegrationTests/SourceGenerationNonAotTests.cs — adds two [TestMethod]s (Overload()/Overload(int)) to an embedded synthetic test-project string, sets <MSTestSourceGenMode>ReflectionFree</MSTestSourceGenMode> in that same embedded .csproj string, and asserts on File.ReadAllText of generated .g.cs files under the asset's own obj/ output — all within the acceptance test's dedicated per-asset scratch directory (generator.TargetAssetPath), so no shared/relative path collision.

The [assembly: Parallelize(...)] literals found via grep in MSTestReflectionMetadataGeneratorTests.cs (lines ~1391–1481) are all inside userCode/MinimalMSTestStub string constants fed to the source generator under test — synthetic input, not a real compiled attribute on the MSTest.SourceGeneration.UnitTests assembly itself. Correctly excluded per the workflow's validation rule; not a configuration change.

No .runsettings, testconfig.json, Directory.Build.props/.targets, or .csproj parallelization settings were touched by this PR.

_{Advisory only — heuristic, non-blocking. Re-run with /parallel-audit. This audit answers "is it parallel-safe?"; for testability, smells, or flakiness see the detect-static-dependencies / test-smell-detection / test-anti-patterns analyses.}

🤖 Automated content by GitHub Copilot. Generated by the Parallel-safety audit on PR (on open / sync) workflow. · auto · 73.3 AIC · ⌖ 4.73 AIC · ⊞ 24.8K · [◷]( · ◷)

[github-actions]

🧪 Expert test review — PR #10545

Grade	Test	Mutation	Notes	How to improve
B (80–89)	mod MSTestReflectionMetadataGeneratorTests. Generator_ OverriddenVirtualMethod_ HonorsInheritedAttributeUsage	3/4 killed	Confirms the base [DataRow(1)] isn't duplicated onto the override, but never asserts it's still emitted for the base method.	Assert the registry still contains DataRowAttribute(1) for the base method.
A (90–100)	mod MSTestReflectionMetadataGeneratorTests. Generator_ DoesNotEmitRedundantDataRowsDescriptor	2/2 killed	Checks both support-types and registry sources exclude the removed DataRows descriptor.	—
A (90–100)	mod MSTestReflectionMetadataGeneratorTests. Generator_ EmitsDataRowAttributeWithoutDuplicateArgumentArray	2/2 killed	Asserts the exact emitted DataRowAttribute construction and absence of the old DataRows array.	—
A (90–100)	mod MSTestReflectionMetadataGeneratorTests. Generator_ EmitsMultipleDataRowAttributes_ InDeclarationOrder	3/3 killed	Verifies each generated DataRowAttribute and that declaration order is preserved via index comparisons.	—
A (90–100)	mod MSTestReflectionMetadataGeneratorTests. Generator_ LeavesDataRowParamsMaterializationToAttribute	2/2 killed	Confirms the variadic params tail is passed straight through to the attribute constructor, not pre-flattened.	—
A (90–100)	mod MSTestReflectionMetadataGeneratorTests. Generator_ EmitsModuleInitializer_ RegisteringAssemblyWithAttributes_ AndCompilesAgainstHook	4/4 killed	Broad assertions pin the new cached-array ResolveMethod/ResolveProperty pattern and reject the old per-call GetMethods(flags) call.	—
A (90–100)	mod MSTestReflectionMetadataGeneratorTests. RuntimeRegistration_ RegistersCompleteMethodAttributes	2/2 killed	Ordering assertions (resolvedGuard < completenessGuard < assignment) protect the guard sequencing, not just presence.	—
A (90–100)	mod SourceGenerationNonAotTests. SourceGenerationNonAot_ BuildsAndRunsTests_ WithExitCodeZero	N/A	End-to-end acceptance test now also asserts generated-file contents (no DataRows/ParameterNames) and an updated pass count reflecting the new Overload test methods.	—

_{This advisory comment was generated automatically. Grades are heuristic
and informational — they do not block merging. Suggestions on the Files
changed tab can be applied with one click. Re-run with
/review-tests.}

🤖 Automated content by GitHub Copilot. Generated by the Test Reviewer on PR (on open / sync) workflow. · auto · 115.2 AIC · ⌖ 10.8 AIC · ⊞ 16.9K · [◷]( · ◷)

[github-actions]

🤖 Automated content by GitHub Copilot. Generated by the Test Reviewer on PR (on open / sync) workflow. · auto · 115.2 AIC · ⌖ 10.8 AIC · ⊞ 16.9K · ◷