perf(assertions-source-gen): make assertion generators properly incremental

[thomhurst]

Summary

The assertion source generators (TUnit.Assertions.SourceGenerator and TUnit.Assertions.Should.SourceGenerator) did not cache between edits. Some of their pipeline models held symbols, so the models never compared equal and also kept old compilations alive. One step ran a semantic transform on every class in every project that references TUnit. Another walked the whole current assembly three times on each compilation. This PR moves these generators to equatable, symbol-free models and narrower providers.

For the same input, generated output is byte-identical. I built TUnit.Assertions and TUnit.Assertions.Should with EmitCompilerGeneratedFiles for netstandard2.0, net8.0, net9.0 and net10.0, before and after this change. All 944 generated files match (diff -r is empty). No snapshot changed.

Changes

1. AssertionMethodGenerator
   • AssertionFrom<T> is now found with ForAttributeWithMetadataName("TUnit.Assertions.Attributes.AssertionFromAttribute1"). The previous CreateSyntaxProvider(node is ClassDeclarationSyntax)ranGetDeclaredSymbolandGetAttributes` on every class.
   • The generators build against Roslyn 4.7 only, and generic attribute metadata names work with FAWMN there. The new GenericAndNonGenericAttributesAreDiscovered test covers this with the 4.7 driver used by the incremental test project.
   • Both FAWMN transforms now return string-only records (AssertionClassModel → AssertionEntryModel → ConditionClassModel, using the existing ImmutableEquatableArray).
   • Each [AssertionFrom] entry is rendered in the transform: its condition classes keyed by class name, its extension methods, and the "method not found" message. The output step keeps the same cross-class dedup of condition class names, the same grouping, and non-generic data before generic data. Output is identical.
   • I rendered snippets instead of building a structured model because the roughly 900 lines of emission code are tightly bound to symbols. Rewriting them would have been a large, risky change for the same caching result.
   • The Select(... AsEnumerable()) that always produced a new value is gone.
2. AssertionExtensionGenerator
   • AssertionExtensionData no longer holds two INamedTypeSymbol values and an ImmutableArray<IMethodSymbol>.
   • The transform now extracts equatable records: class name and namespace, return type, generic params and constraints, a receiver-type record, and per-constructor records. Each constructor record holds its parameters (type, name, formatted default), its resolved RequiresUnreferencedCode message and the pinned-overload decision.
3. MethodAssertionGenerator
   • The transform returns an equatable DiagnosticInfo (descriptor, file path, text span, line span and string args) instead of a Diagnostic. The output step pairs each diagnostic with the compilation and reattaches it to the matching syntax tree (Location.Create(tree, span)), so #pragma and per-file severities still apply. It falls back to Location.Create(path, span, lineSpan) only when no single tree has that path. Because each diagnostic is paired individually, this output only re-runs while diagnostics exist.
   • methods.Collect() is now grouped per containing type (SelectMany to ContainingTypeGroup), with one source output per group. An edit re-emits only the affected type's file. Hint names and file contents are unchanged.
4. ShouldExtensionGenerator
   • I checked the semantics first. Only top-level, public, non-generic static classes can contribute. Nested static classes cannot declare extension methods.
   • Current-compilation extension containers now come from a syntax provider. It only accepts top-level classes that declare a method whose first parameter has this.
   • Wrappers come from ForAttributeWithMetadataName(ShouldGeneratePartialAttribute). CollectWrapper was split, and the single-type part (DescribeWrapper) is shared with the reference scan. GetAttributes() is no longer called on every type.
   • Both syntax steps return only the type's metadata name. A container's output depends on its returned assertion types, and a wrapper's output depends on the wrapped assertion's methods and constructors. Either can be declared in another file. So a ShouldLocalDeclarations step resolves the names against each compilation and runs CollectFromContainer/DescribeWrapper for the candidates only. Partial types are deduplicated by name. The result is equatable, so outputs stay cached when nothing relevant changed.
   • CollectExistingShouldEntryKeys uses assembly.GetTypeByMetadataName("TUnit.Assertions.Should.ShouldExtensions") instead of walking every type. It still does so for referenced assemblies.
   • The ReferencesAssertionsAssembly pre-filter result is cached per MetadataReference in a second ConditionalWeakTable, validated against the TUnit.Assertions identity.
   • The CompilationProvider step now only does cheap lookups and merges cached per-reference data, and its result is equatable.
5. Incremental tests (tests/TUnit.SourceGenerator.IncrementalTests)
   • Added WithTrackingName steps to the generators and helpers in TestHelper.
   • New tests for AssertionMethodGenerator, AssertionExtensionGenerator and ShouldExtensionGenerator. Two MethodAssertionGenerator tests were added: a per-type regeneration test, and a test that an unrelated edit does not regenerate when a diagnostic is present.
   • Adding or editing an unrelated type leaves the tracked steps Cached or Unchanged, and no source output re-runs. A relevant edit marks the step Modified and updates the output. For the multi-class cases, only the edited class's output re-runs.
   • The Should generator is referenced with Aliases="ShouldGenerator". It compiles a linked copy of EquatableArray that would otherwise conflict with TUnit.Core.SourceGenerator's copy.

Behaviour notes (edge cases only; no effect on TUnit's own output)

• AssertionFrom<T> on a partial class: attributes now come from the attributed declaration, which is how the non-generic path already worked. Before, each declaration re-read every part's attributes, which duplicated members when a partial class was split.
• In the Should generator, current-compilation items now follow syntax order instead of symbol-namespace-walk order. That order is only visible when two containers with the same simple name in different namespaces merge into one Should{Name} file.
• MethodAssertionGenerator diagnostics are still reported at a tree location. The pipeline carries only the path and span, and the tree is looked up in the current compilation at output time, so no old tree is rooted.

Tests run

• tests/TUnit.Assertions.SourceGenerator.Tests: 279/279 passed (net48, net8, net9, net10), no snapshot changes.
• tests/TUnit.Assertions.Should.SourceGenerator.Tests: 144/144 passed, no snapshot changes.
• tests/TUnit.Assertions.Tests: 6619/6619 passed.
• tests/TUnit.Assertions.Should.Tests: 408/408 passed.
• tests/TUnit.PublicAPI: the Assertions and Should API tests pass. OpenTelemetry_Library_Has_No_API_Changes fails locally on net8/9/10 with a "PATH_SCRUBBED" +\n "" line-wrap difference. It comes from the long worktree path, is unrelated to this change, and nothing was committed for it.
• tests/TUnit.SourceGenerator.IncrementalTests: 30/30 passed. This project is VSTest-based and isn't run by dotnet test under the MTP-only global.json, so I ran it with dotnet vstest and the xunit adapter. It includes cross-file tests: editing the wrapped assertion, or the assertion a container returns, in another file regenerates the Should output. It also checks that the diagnostic location keeps its SourceTree.
• Generated-output diff for TUnit.Assertions and TUnit.Assertions.Should across all 4 TFMs: identical.

Skipped

Nothing. All five items were checked against the code and applied.

Summary by CodeRabbit

• Improvements
  • Assertion source generation reuses cached results when unrelated code changes and regenerates output only for affected assertion types.
  • Changes to assertion extensions and wrappers are tracked independently, limiting regeneration to relevant generated output.
  • Assertion diagnostics retain their original source locations when unrelated files change.
  • Generated Should assertions now support methods declared in C# extension blocks.

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-28T18:59:10.172239Z	9b2de6a	PR opened

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📝 Walkthrough

Walkthrough

Four source generators now use narrower incremental data models and output scopes. The changes add local declaration tracking, value-based generation data, per-type grouping, diagnostic reconstruction, and tests for cache behavior and targeted regeneration.

Changes

Source generator pipelines

Layer / File(s)	Summary
Collect and merge Should declarations src/TUnit.Assertions.Should.SourceGenerator/ShouldExtensionGenerator.cs, tests/TUnit.SourceGenerator.IncrementalTests/ShouldExtensionGeneratorIncrementalTests.cs, tests/TUnit.Assertions.Should.Tests/UserDefinedAssertionTests.cs, tests/TUnit.SourceGenerator.IncrementalTests/TUnit.SourceGenerator.IncrementalTests.csproj	The generator separates local declarations from compilation data, caches reference checks, resolves ShouldExtensions directly, and merges methods and wrappers. Tests cover cache behavior, targeted updates, extension blocks, and wrapper resolution.
Flatten assertion extension data src/TUnit.Assertions.SourceGenerator/Generators/AssertionExtensionGenerator.cs, tests/TUnit.SourceGenerator.IncrementalTests/AssertionExtensionGeneratorIncrementalTests.cs	The pipeline stores type, receiver, constraint, constructor, parameter, and trimming metadata as values. Generation consumes the stored data. Tests check cached outputs and targeted regeneration.
Render assertion attribute models src/TUnit.Assertions.SourceGenerator/Generators/AssertionMethodGenerator.cs, tests/TUnit.SourceGenerator.IncrementalTests/AssertionMethodGeneratorIncrementalTests.cs	Attribute discovery produces rendered models for generic and non-generic assertions. Emission groups entries by class and reports stored missing-method messages. Tests check independent updates and cached outputs.
Group method assertions by containing type src/TUnit.Assertions.SourceGenerator/Generators/MethodAssertionGenerator.cs, tests/TUnit.SourceGenerator.IncrementalTests/MethodAssertionGeneratorIncrementalTests.cs	Method assertions generate per containing type. Diagnostics reconstruct locations from stored path and span data. Tests check targeted output changes and diagnostic stability.
Track incremental generator results tests/TUnit.SourceGenerator.IncrementalTests/TestHelper.cs, tests/TUnit.SourceGenerator.IncrementalTests/TUnit.SourceGenerator.IncrementalTests.csproj	The test project references the Should generator and adds shared assertions for tracked-step and source-output run reasons.

Priority: ⬇️ Low

Estimated code review effort: 4 (Complex) | ~50 minutes

Change: Refactor

Merge Risk: 🟡 Moderate · up to 6e212

Generated methods are not added to nested Should wrappers and can fail to compile. Fix nested-wrapper emission before merging.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 6e212

The generators will do less work after edits while continuing to check which declarations qualify for generated methods. No new sensitive runtime access or demonstrated security regression was found, but output equivalence across every dependent project has not been independently established.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — A project supplying declarations to the generator can affect its own generated public assertion methods and downstream consumers of that generated code; the inspected path does not introduce a runtime privileged sink.

Trust Boundaries and Controls

• observed — Source declarations are filtered semantically before emission, and cached reference-prefilter results are tied to the current assertions assembly identity.

Resilience and Maintainability Implications

• observed — The reference prefilter computes a result before cache publication; a competing cache insertion does not replace the current invocation's computed result.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 13.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 90 functions across 10 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: improving the incremental behavior of the assertion source generators.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[github-actions]

Review

I read the diff and skimmed AssertionMethodGenerator.cs in the PR head. I didn't build or run the tests. The skill-based review tool errored, so this is a manual review.

Overall: the design is sound.

• Symbol-free models. Symbols now stay inside the transforms. CreateAssertionAttributeData is documented as never flowing through the pipeline. The pipeline carries string-only equatable records built on the existing ImmutableEquatableArray. That fixes both problems in the description: models that never compare equal, and old compilations staying alive.
• Narrower providers. ForAttributeWithMetadataName replaces the CreateSyntaxProvider that ran GetDeclaredSymbol on every class. That is the main per-keystroke cost.
• Generic attribute names. The GenericAndNonGenericAttributesAreDiscovered test covers the Roslyn 4.7 concern for generic attribute metadata names.
• Verification. The byte-identical comparison of 944 generated files across four target frameworks, with no snapshot changes, is strong evidence that behaviour is preserved.
• Incremental tests. The new cache tests for all four generators are what stop this from regressing.

Non-blocking notes:

1. Rendering source snippets in the transform (as the description explains) moves the string-building cost into the transform, where it runs for each changed class. It gives cheap equality and simple models. The trade-off is that any change to a class re-renders its snippets. That is fine here, but a comment saying it is deliberate would help future maintainers.
2. Location.None is still used for the "method not found" diagnostic. That was already the case, but diagnostics without a location are harder to act on. If you can carry an equatable location (file path plus text span) in the model, the diagnostic would point at the attribute.
3. The Should generator's semantic transform was also narrowed. Please confirm its incremental test asserts that an unrelated edit produces Unchanged or Cached for every tracked step, not just the final output.

No blocking issues. LGTM.

[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: 9b2de6ae1e

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[greptile-apps]

Confidence Score: 5/5

[Medium risk] Refactors assertion source generators for incremental compilation.

The PR appears safe to merge; no outstanding findings or new actionable issues remain.

Summary

The PR makes the assertion generators more incremental by replacing symbol-bearing pipeline models with equatable data, narrowing declaration discovery, and reattaching diagnostics to current syntax trees. Changes since the previous review address file-local wrappers and escaped identifiers.

_{Reviews (7) · Last reviewed commit: "fix(assertions-source-gen): escape keywo..."}

[github-actions]

Review

The change is well scoped and well argued: symbol-free equatable models, ForAttributeWithMetadataName in place of per-class semantic transforms, and byte-identical output on 944 files across four TFMs. The new incremental tests cover the caching behaviour. I reviewed the diff and read MethodAssertionGenerator in full. I did not build the project or run the tests.

Points worth considering (none blocking):

1. Diagnostic reattachment (DiagnosticInfo.ToDiagnostic). diagnostics.Combine(CompilationProvider) re-runs for each diagnostic on every compilation change. That is acceptable because it only happens while diagnostics exist. The path-matching loop is O(trees) per diagnostic. If there are many errors in a large project, resolve a path → tree map once per compilation, for example CompilationProvider.Select into a dictionary. Duplicate paths would map to null. The TextSpan.End <= match.Length guard is a good defensive check. The fallback to Location.Create(path, span, lineSpan) loses #pragma handling, but that is documented and rare.

2. Rendering snippets in the AssertionMethodGenerator transform. I understand the reason: about 900 lines of emission are bound to symbols. It does mean the model is effectively pre-rendered text, so any small edit to a condition class re-renders and re-emits the whole entry. That is fine for caching, since the model compares by value. As a follow-up, a structured model would make the transform testable without going through strings.

3. GroupByContainingType. It groups by FullContainingType and takes First() for the containing type. If two partial declarations of the same type or identically named types in different namespaces produce different ContainingTypeData, the first one wins silently. This should be fine given FullContainingType, but a short comment on the assumption would help. Also confirm that hint names stay unique per group. The PR says they are unchanged, which suggests they are.

4. ShouldExtensionGenerator syntax filter. It accepts only top-level classes with a this-parameter method. Please keep a test for a static partial class split across files, where only one part declares the extension method. I can't tell from the diff whether one exists.

Overall this is a solid improvement. The tests and the identical-output verification give me good confidence. Approving from my side.

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Actionable comments posted: 1

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Inline comments:
Review comments at
@src/TUnit.Assertions.SourceGenerator/Generators/MethodAssertionGenerator.cs:
- Around line 1420-1424: Update the tree-matching logic in
MethodAssertionGenerator so pathless files retain a stable way to identify the
originating SourceTree instead of clearing an ambiguous match. Ensure
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Reviewing files that changed from the base of the PR and between 9b2de6a and ffe0f02.

📒 Files selected for processing (4)

• src/TUnit.Assertions.Should.SourceGenerator/ShouldExtensionGenerator.cs
• src/TUnit.Assertions.SourceGenerator/Generators/MethodAssertionGenerator.cs
• tests/TUnit.SourceGenerator.IncrementalTests/MethodAssertionGeneratorIncrementalTests.cs
• tests/TUnit.SourceGenerator.IncrementalTests/ShouldExtensionGeneratorIncrementalTests.cs

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[github-actions]

Review

I checked this against the diff but did not build it or run the tests. The design is sound.

What I checked

• The models are now string-only and equatable, with no ISymbol or Location held in pipeline values. That is what makes incremental caching work.
• ForAttributeWithMetadataName replaces the per-class CreateSyntaxProvider, so the semantic transform no longer runs on every class.
• DiagnosticInfo stores the file path, text span and line span instead of a Location. It rebuilds the location from the compilation, so diagnostics keep their source positions. The tests assert this with SourceTree and line checks.
• The PR description says the generated output is byte-identical across 944 files and that no snapshots changed. That is a strong check for a refactor this size. I did not re-verify it.
• The new incremental tests cover cache hits and targeted regeneration. They also cover generic and non-generic [AssertionFrom].

Suggestions (non-blocking)

1. diagnostics.Combine(context.CompilationProvider) in the diagnostics output step reruns whenever the compilation changes. It is cheap, but it reintroduces a compilation dependency. Rebuilding the location only needs the syntax tree. Resolving it lazily, only when Location.IsInSource matters, or falling back to Location.Create(FilePath, ...) would drop the dependency. Consider adding a test that this step stays cached when an unrelated file changes.
2. ShouldExtensionGenerator still reads referenced assemblies from CompilationProvider, as the comment in the code says. CompilationDataStep narrows this, but it still runs on every edit. It would be good to confirm the step returns Unchanged for edits that don't touch references, since the cache value is only useful if the equality comparison holds.
3. Rendering snippets as strings in the transform is a reasonable trade against a structured model. It does mean that changing the emit format changes cached model equality. That is harmless, but worth a short comment near the record definitions so nobody adds unstable content such as timestamps or ordering-dependent collections.

Overall this is a good change and I don't see blocking issues.

[thomhurst]

Follow-up on the non-blocking review notes, in a8dc94e:

• Split partial Should container: added PartialContainerSplitAcrossFilesGeneratesAllMethodsOnce. FooExtensions is split over three files, two with extension methods and one without. Each Should method is emitted once. Editing the part without extension methods leaves the containers, declarations and payload steps and all outputs cached.
• Rendered snippets in AssertionMethodGenerator: added a remark on AssertionEntryModel saying the rendering is deliberate and the text must stay deterministic.
• GroupByContainingType taking First(): added a comment. The group key is the fully qualified name, and ContainingTypeData is only name, full name and namespace, so every entry in a group is identical. Hint names are unchanged.
• Should step caching on unrelated edits: already covered. AssertUnchanged asserts Cached/Unchanged for every tracked step (containers, wrappers, declarations, compilation data, payload) plus the source outputs.
• diagnostics.Combine(CompilationProvider): leaving as is. It only runs while diagnostics exist, and it needs the compilation's trees to keep a source-backed location for pragma and editorconfig suppression. A Location.Create(path, …) fallback would lose that, which is the earlier Codex finding.

[github-actions]

Review of #6916

I read the ShouldExtensionGenerator changes closely. I only skimmed the AssertionMethodGenerator, AssertionExtensionGenerator and MethodAssertionGenerator changes. I did not build the branch or run the tests. The PR reports byte-identical output across 944 generated files and no snapshot changes, and I did not re-check that.

The approach is sound. It replaces symbol-holding pipeline models with string-only equatable records and narrows the providers (FAWMN, plus a syntactic gate for extension containers). It also adds tracking-name incremental tests. CompilationData and LocalDeclarations are split so that only the affected step reruns.

Points to consider (none blocking):

1. Extension-block gap in IsExtensionContainerCandidate. It only recognises MethodDeclarationSyntax members whose first parameter has this. That matches the old walk for classic extension methods. The repo builds with preview C#, so if C# 14 extension(T x) { ... } blocks are ever used to declare Should extensions, they would now be silently skipped. Either add a test or comment pinning this as intentional, or accept extension-block members in the gate. A false positive here only costs a cheap semantic lookup.
2. s_prefilterCache remove-then-add. The Remove followed by Add with a catch (ArgumentException) works. ConditionalWeakTable.AddOrUpdate is available on netstandard2.0 in recent runtimes, but not on every target this generator ships for. If it is available, it is simpler than the try/catch. If not, the current code is fine.
3. GetMetadataName. It hand-builds the name that GetTypeByMetadataName expects. Nested types and generic arity are handled through MetadataName. A small test with a nested or generic container would guard against regressions, if one does not already exist.
4. CollectExistingShouldEntryKeys. It now uses GetTypeByMetadataName(ShouldExtensionsTypeFullName). If the same type name is defined in multiple referenced assemblies, GetTypeByMetadataName returns null on ambiguity. This is called on compilation.Assembly and on each refAssembly, so it is per-assembly and safe. It differs from the old walk only for duplicate definitions within a single assembly, which cannot happen.

Overall this is a solid perf and cache-correctness improvement. Approve, subject to the extension-block question in point 1.

[thomhurst]

Thanks for the review. Addressed in 6e21299:

1. Extension blocks in IsExtensionContainerCandidate. I checked this against main by running both the old and the new generator on a Roslyn 5.9 compilation containing an extension(IAssertionSource<int> source) { ... } block. The old namespace walk did pick it up (the block's members surface on the container as extension methods), and the new gate was dropping it, so it was a real regression. The gate now also accepts extension-block members. The syntax kind is resolved by name from the host compiler, because the generator is built against Roslyn 4.7, which predates the syntax. On older compilers nothing changes. I pinned this with an end-to-end test in TUnit.Assertions.Should.Tests that declares an assertion through an extension block and calls .Should().BeOddViaExtensionBlock(). Without the fix, that test fails to compile with CS1061. The generator test projects can't cover it directly because they parse with Roslyn 4.7.
2. s_prefilterCache Remove-then-Add. I kept this as is. ConditionalWeakTable.AddOrUpdate/TryAdd aren't available on netstandard2.0, and the Polyfill version we use only adds a Remove(key, out value) overload. A lost race just means the next lookup sees an identity mismatch and recomputes, so the result stays correct.
3. GetMetadataName. I added GenericAndNestedWrappersResolveByMetadataName. It covers a dotted namespace, a generic wrapper (arity suffix) and a wrapper nested in a generic outer type (+ separator). I checked that swapping + for . makes it fail.
4. No action needed.

Tests: TUnit.Assertions.Should.SourceGenerator.Tests (144), TUnit.Assertions.SourceGenerator.Tests (279), TUnit.Assertions.Should.Tests (411 across net8/9/10) and TUnit.SourceGenerator.IncrementalTests (33) all pass. No snapshot changes.