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fix(generic): infer method type arguments from [Arguments<T>] rows in both modes - #7343
On a generic test method, a typed [Arguments<T>] row was not used to infer type arguments in source-generated mode. Neither the [Arguments] row inference (HasArgumentsArray is false for Arguments<T>) nor the typed-source inference (it recognised only DataSourceGeneratorAttribute / AsyncDataSourceGeneratorAttribute bases, and ArgumentsAttribute<T> derives from TypedDataSourceAttribute<T>) handled it. On current main the row was reported as "Could not infer the type arguments" (since #7163); earlier it was silently dropped. Reflection mode ran it.
Changes:
A typed row (a TUnit.Core.TypedDataSourceAttribute<T> with no DataSourceGeneratorAttribute / AsyncDataSourceGeneratorAttribute base, such as [Arguments<T>]) now infers the method type arguments by matching T against the data parameters, excluding any CancellationToken. The whole row binds to a single data parameter; otherwise each tuple element binds to one data parameter, with generic type arguments nested in the parameter types matched as well. Every type parameter must be inferred, each to exactly one type. [Arguments<int[]>] on Run<T>(IEnumerable<T>) therefore infers nothing, rather than an uncallable Run<int[]>. A tuple row (a one-element ValueTuple included) always spreads over the data parameters, as ToObjectArray spreads it before invocation; an object[], System.Tuple or other ITuple row (which DataSourceHelpers.IsTuple spreads without declaring element types) infers nothing. Omitted trailing optional parameters (params arrays and params collections included) are allowed, a Func<T>, TestDataRow<T> (or a type deriving from it) or TestDataRow<Func<T>> row binds as its T because it is invoked and unwrapped before invocation (a reference-type array T there is spread by UnwrapArray, so its element binds; an object element type infers nothing), and a T? parameter takes a row of its underlying type. A nullable tuple row infers nothing in either mode: a non-null value boxes to the tuple and spreads, but a null one binds whole, so Run<int> would turn it into 0. Reflection mode infers each such row from its value; source-generated mode reports the Source-gen silently drops a generic test method when its type arguments cannot be inferred from the data source #7163 cannot-infer failure. A typed [Arguments<T[]>] row is never read as an untyped [Arguments] params array.
In the generator and analyzer TUnit0001, this lives in TypedDataSourceInference.InferMethodTypeArgumentsFromRowType. TestMetadataGenerator.InferTypesFromDataSourceAttribute calls it on generic classes too. The class-only inference path (a non-generic method of a generic class) and the generator-base rules are unchanged.
With a method [GenerateGenericTest], an [Arguments<T>] row whose types another source already instantiated now joins that instantiation in reflection mode, in declaration order. The generator already joined it, because its name matches ArgumentsAttribute, so both modes now run the row instead of reflection dropping it.
Tests
New tests/TUnit.TestProject/Bugs/_7214 cases and tests/TUnit.Engine.Tests/Issue7214Tests.cs (both modes): [Arguments] with [Arguments<int>] in either order, two [Arguments<int>] rows, a generic class closed by [GenerateGenericTest], and method [GenerateGenericTest] variants, including a typed row of a different type, a declared object row on Run<T>(T), an [Arguments<int[]>] row on an IEnumerable<T> parameter, a row with a trailing optional parameter, a row on a T? parameter, a row with an omitted C# 13 params collection, a typed source of TestDataRow<int> rows (unwrapped to T, as at invocation), a typed source of rows of a record deriving from TestDataRow<int> (unwrapped the same way), and typed sources of Func<int> and TestDataRow<Func<int>> rows (invoked to int), a typed source of ValueTuple<int> rows (spread to int), a typed source of ValueTuple<TestDataRow<int>> rows (spread, then unwrapped to int), a typed source of TestDataRow<string[]> rows (spread to string), a null [Arguments<string[]>] row (only Run<string[]>, no untyped Run<object>), and a typed source of ITuple rows (not closed as Run<ITuple>: reflection infers Run<int> from the value, and source-generated mode reports the Source-gen silently drops a generic test method when its type arguments cannot be inferred from the data source #7163 cannot-infer failure, so the class has no [EngineTest] attribute), and a typed source of non-null and null ValueTuple<int>? rows (reflection runs Run<int>(1) and Run<object>(null); source-generated mode reports cannot-infer).
Ran locally (net10.0): the _7214 tests in source-gen and reflection modes (30 tests: reflection 30/30; source-gen 27/27 plus the expected cannot-infer failures of TypedITupleRowSource and the two TypedNullableTupleRowSource rows), the TUnit.Core.SourceGenerator.Tests snapshots (no changes), and TUnit.Analyzers.Tests. TUnit.Engine.Tests builds; its run is left to CI, per AGENTS.md.
Fixed generic tests using typed argument rows so method type parameters can be inferred from row data.
Typed rows now work alongside regular argument rows, including on generic test classes and with generated tests.
Improved inference for tuples, nullable values, collections, optional and params parameters, and typed data sources.
When row data does not provide enough information for inference, the test runner avoids making an unsupported inference. Some tuple shapes are left to runtime inference.
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Walkthrough
Source generation and reflection now infer generic method type arguments from typed data-source rows. Reflection discovery also retains compatible typed argument rows in existing instantiations. Regression tests cover row shapes, parameter binding, generic classes, and mode-specific outcomes.
Source generation infers method type arguments from typed row shapes and method parameters. Matching handles tuples, scalar rows, nested generic types, optional parameters, and row wrappers. Typed array rows are excluded from non-generic argument-array detection.
Reflection inference and row collection src/TUnit.Engine/Discovery/ReflectionTestDataCollector.cs
Reflection discovery infers method type arguments from typed rows and method parameters. Compatible typed argument rows join existing instantiations without duplicates, in declaration order.
thomhurst/TUnit#7372: The issue concerns source-generated invocation of a typed TestDataRow<Tuple<int>[]> after generic inference, which continues the typed-row behavior changed here.
Possibly related PRs
thomhurst/TUnit#7322: It changes generated type information for nullable generic parameters, which overlaps with this PR’s nullable-parameter inference cases.
thomhurst/TUnit#7341: It changes runtime tuple-row binding rules, which overlap with this PR’s tuple inference and parameter-shape cases.
Suggested reviewers:kenny-ish
Merge Risk: Minimal · up to e0738
No actionable merge-blocking risk remains from the reviewed changes.
Pre-merge checks: 4 · 1
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Docstring coverage is 54.55% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documenta…
Write docstrings for the functions missing them to satisfy the coverage threshold.
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Title check
The title clearly and concisely describes the main change: generic method type inference from [Arguments] rows in both reflection and source-generated modes.
Linked Issues check
Directly linked issue #7214 requires source-generated mode to run a typed [Arguments<T>] row on a generic test method when the row infers the same method type arguments as another row. Reflection mo…
Out of Scope Changes check
The incremental change only refactors the ITuple check in ReflectionTestDataCollector.cs into the IsITuple helper with a netstandard2.0-compatible fallback. This supports the typed-row inferen…
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Explanation
Directly linked issue #7214 requires source-generated mode to run a typed [Arguments<T>] row on a generic test method when the row infers the same method type arguments as another row. Reflection mode already does this. The whole-PR changes keep that behavior: TypedDataSourceInference.InferMethodTypeArgumentsFromRowType infers method type arguments from typed rows, and TestMetadataGenerator routes typed-row bases to it. The _7214 regression corpus and Issue7214Tests.cs cover the #7214 shape in both modes. The incremental change since the previous reviewed head (327d20b) moves the ITuple row check into a helper, IsITuple, in ReflectionTestDataCollector.cs. On NET targets the helper performs the same ITuple.IsAssignableFrom check as before. On non-NET targets it matches the type by full name, because ITuple is not referenced there. This does not change matching on NET targets, so the earlier conclusion still holds.
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The incremental change only refactors the ITuple check in ReflectionTestDataCollector.cs into the IsITuple helper with a netstandard2.0-compatible fallback. This supports the typed-row inference that #7214 requires, so it stays in scope. The whole-PR changes remain limited to typed-row inference in the generator, analyzer, and reflection collector, plus the _7214 regression tests and Issue7214Tests.cs. No unrelated feature or behavior change is evident in the reviewed diffs. Repository inspection did not cover the full source tree beyond these diffs, so this verdict rests on the reviewed diff and the prior review.
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Docstring coverage is 54.55% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentation-only edits and deletions within surviving functions are included; unchanged diff context and fully deleted functions are excluded. Analyzed 33 functions across 5 files.
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Write docstrings for the functions missing them to satisfy the coverage threshold.
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A rabbit checks each typed row, Tuples hop where parameters go. Generic types settle in place, Rows join their matching case. The tests run through the burrow tonight. All values land just right.
Reviewed the diff. I didn't build it or run the tests myself.
The fix is small and targeted. [Arguments<T>] derives from TypedDataSourceAttribute<T>, which neither inference path recognised. The PR adds that base to the shared IsTypedDataSourceBase helper, which the generator and analyzer TUnit0001 both use. It also adds it to the generic-method path in TestMetadataGenerator and to the reflection collector. The two modes should now behave the same, as AGENTS.md requires. Tests cover both modes and include these cases:
Rows in either order.
Two typed rows.
A generic class.
[GenerateGenericTest] with a typed row of a different type.
Minor, non-blocking suggestions:
Extra pattern in TestMetadataGenerator. The isGeneratorBase || (method.IsGenericMethod && ...) check adds a second pattern next to the shared helper. Calling TypedDataSourceInference.IsTypedDataSourceBase there would stop the three places drifting apart. The namespace check is also a loose Contains("TUnit.Core"). That predates this PR, but the shared helper compares exactly.
Sort in the reflection collector. The existingRows.Sort call uses List.Sort, which is unstable. That is fine as long as DeclarationIndex values are unique. If two rows can share an index, an ordered insert would be safer.
Doc comment. The comment on the ReflectionTestDataCollector method has become one very long line. Wrapping it would help readability.
The fix is sound and focused. [Arguments<T>] derives from TypedDataSourceAttribute<T>, and the PR teaches the generator, the analyzer (through the shared IsTypedDataSourceBase) and reflection mode to treat that base as a typed source. The engine tests run both modes and cover the ordering, generic-class and [GenerateGenericTest] variants.
Points to consider (non-blocking):
Check for other TypedDataSourceAttribute<T> subclasses. The match on the base name is now broader. Today the DataSourceGenerator/AsyncDataSourceGenerator bases and ArgumentsAttribute<T> are the only subclasses I found in src. A user-defined direct subclass would now also infer from T, which seems right. It is worth confirming that the first type argument is always the row type. For a tuple-based base it is (T1, T2) as a single argument, and the new IsGeneratorBase-style check in TestMetadataGenerator appears to handle that the same way as before.
Three places hold the same type list.TypedDataSourceInference, TestMetadataGenerator.InferTypesFromDataSourceAttribute and the reflection collector each repeat the list of recognised base names. The generator's InferTypesFromDataSourceAttribute could call TypedDataSourceInference.IsTypedDataSourceBase instead of keeping its own copy. The method.IsGenericMethod gating there is the only real difference. Sharing the helper would stop the three lists drifting apart, which is how this bug appeared.
Reflection mode sorts on each join.existingRows.Sort with DeclarationIndex runs on every joining row. That is fine for discovery. Note that List.Sort is unstable, but the keys are unique declaration indexes, so order is deterministic.
Small cleanup. The XML doc comments in TypedDataSourceInference.cs and ReflectionTestDataCollector.cs now have very long lines. Wrapping them would help readability.
Overall this looks good to merge, and the IsTypedDataSourceBase deduplication would be a nice follow-up.
I read the source diff. I did not build the PR or run its tests.
The change is well scoped and handles the case in #7214. The generator and analyzer share TypedDataSourceInference. The hasGeneratorBase guard means [Arguments<T>] is treated as a row base only when no generator base came first. That avoids misclassifying the generator attributes that also derive from TypedDataSourceAttribute<T>. The inference rules are documented and cover the cases that would otherwise go wrong. A single data parameter takes the whole row. Several parameters take one tuple element each. CancellationToken is excluded. Nested generic arguments are matched. Conflicting bindings return null. Both modes have tests.
Suggestions (non-blocking):
Duplicated algorithm.InferMethodTypeArgumentsFromRowType / MapTypeParameters and the reflection InferTypesFromTypedRow / MapTypedRowParameters are parallel implementations. The doc comments say they mirror each other, but nothing enforces that. Because AGENTS.md requires both modes to behave identically, a test that runs the same matrix through both would catch drift. The existing Issue7214 tests partly cover this. An explicit table of (method signature, row type) → expected arguments would catch more.
Silent mismatch in the matcher. Two cases are worth checking. (a) When MapTypeParameters meets generic types whose definitions differ, for example List<T> against an int[] row, it returns true without binding, and the final "all inferred" check then returns null. That is correct, but a comment saying it is deliberate would help. (b) Arrays and by-ref parameter types (T[] against int[]) are not decomposed, so Run<T>(T[]) with [Arguments<int[]>] infers nothing. This is reasonable, but it is worth stating as a known limitation, or handling, since the C# compiler would infer T=int.
Sort cost in reflection.existingRows.Sort runs on each joined row. That is only a discovery-time cost and probably fine, but a stable insert (or a single sort after the loop) avoids repeated sorting. List.Sort is also unstable, so equal DeclarationIndex values could reorder. That is unlikely here because indices are unique.
No blocking issues found. Looks good to merge once CI is green.
Review of #7343 (typed [Arguments<T>] inference on generic methods)
I read the diff; I did not build it or run any tests.
Overall: the change is sound and well targeted. It fills a real gap, where a typed row was dropped or reported as 'Could not infer'. It also keeps the generator and reflection paths aligned, as the project constraints require.
What looks good
InferMethodTypeArgumentsFromRowType and InferTypesFromTypedRow follow the same rules step for step, so the two modes should behave the same. These rules cover the CancellationToken exclusion, a single parameter taking the whole row, tuple spreading, optional trailing parameters, and T?.
Requiring every type parameter to be inferred, each to exactly one type, avoids uncallable instantiations such as Run<int[]> for IEnumerable<T>. The hasGeneratorBase guard keeps the existing generator-base behaviour unchanged.
The reflection path joins [Arguments<T>] rows into existing instantiations and keeps them in declaration order, matching what the generator emits.
The engine tests cover many combinations, including the generic class case, GenerateGenericTest, declared-type-wins, optional and nullable parameters.
Suggestions (non-blocking)
Drift risk from two parallel implementations. The Roslyn and reflection versions are about 100 lines each. The engine can't reference the generator project, so the duplication is hard to avoid. Both are cheap to unit-test in isolation, though. A small table-driven test run against both implementations (the same method shape and row type, with the expected inferred types) would catch drift sooner than the Engine.Tests integration runs. Those only run in CI.
Missing snapshot or analyzer coverage. Please confirm the generator snapshot tests (.verified.txt) and the TUnit0001 analyzer tests have a case for the new inference. The only new tests I saw are the Engine.Tests and TestProject cases.
Unmatched generic arguments. In MapTypeParameters, if parameterType is generic and valueType is a different generic definition, for example List<T> against int[], the result is silently 'true' with nothing inferred. The final 'all inferred' check catches this, so it is safe. A comment saying so would help the next reader.
Interface and base-class matching. Matching only works when the generic definitions are equal. A row typed List<int> against a parameter IEnumerable<T> infers nothing. This is a conservative choice and the PR says so. It may be worth a note in the docs, or a follow-up issue if users hit it.
Overall this is a solid, well-tested fix. It closes the gap where [Arguments<T>] rows on generic methods were not used for inference in source-generated mode. The generator, analyzer and reflection paths use the same rules. The "each type parameter inferred to exactly one type" rule is a sensible guard (for example int[] on IEnumerable<T>). The tests cover both modes and many edge cases.
I didn't run the tests. I read the diff only.
Observations (non-blocking)
Arrays are not matched structurally.MapTypeParameters and MapTypedRowParameters recurse only into generic named types and Nullable<T>. Run<T>(T[] items) with [Arguments<int[]>(...)] therefore infers nothing, and the user still gets "Could not infer". Arrays are the most common shape after IEnumerable<T>. Handling IArrayTypeSymbol / Type.IsArray (matching rank and element type) is a small addition. It would also fit the stated goal of matching nested types. Also consider by-ref and pointer parameters.
Non-matching shapes silently return true. When the parameter type is a concrete or generic type that doesn't match the value type, the helper returns true without binding anything. The "every type parameter must be inferred" check catches most of these. A mismatch such as Run<T>(List<T>, int) with a (string, int) row can still leave T inferred from elsewhere, and the bad row only fails at invocation. That is probably acceptable, but a comment saying so would help.
Duplicated algorithm. The two copies (Roslyn symbols vs System.Type) must stay in sync by hand, and the doc comments say so. That is unavoidable given the generator/reflection split. A shared test corpus, such as the _7214 classes run in both modes, is the right mitigation and is already present. I'd keep the "Mirrors…" cross-reference comments, as they are.
Cost. The Roslyn version uses LINQ Where().ToArray() and Count, and the reflection version calls GetParameters(), on every call during discovery. Both only run for generic methods, so I don't expect a problem. Still, MethodInfo.GetParameters() allocates a new array each call, so caching it in the surrounding loop would match the hot-path guidance in AGENTS.md.
Sort stability.existingRows.Sort(...) uses List.Sort, which is unstable. DeclarationIndex should be unique per attribute, so this is fine. If it can ever tie, an ordered insert would be safer.
…types (#7214)
A typed row binds to the data parameters, so its declared type is matched against
them instead of being taken whole as the type argument. [Arguments<int[]>] on
Run<T>(IEnumerable<T>) no longer adds a Run<int[]> instantiation that cannot take
the row. Same rules in the generator, analyzer TUnit0001 and reflection mode.
…eters (#7214)
A scalar [Arguments<T>] row binds to the first data parameter when the rest are optional, a tuple row may omit trailing optional parameters, and a T? parameter takes a row of its underlying type. Applied in both the generator and reflection mode.
…typed-row inference (#7214)
A typed source of TestDataRow<T> rows inferred Run<TestDataRow<T>> in both
modes, but the row is unwrapped before invocation, so the T value could not
bind. Both modes now match the row's T.
Reflection counted an omitted C# 13 params collection as required, so a scalar
typed row was rejected there while the generator (Roslyn IsParams) accepted it.
Review of #7343 (typed [Arguments<T>] row inference on generic methods)
The fix is correct in approach and well covered. I found no blocking issues.
What I checked
The generator (TypedDataSourceInference.InferMethodTypeArgumentsFromRowType) and the reflection path (InferTypesFromTypedRow) apply the same rules: single data parameter, tuple spread, scalar to the first parameter, optional and params handling, TestDataRow<T> unwrap, T?, and 'one type per type parameter'. That meets the repo rule that metadata collection behaves identically in both modes.
The hasGeneratorBase guard stops TypedDataSourceAttribute<T> (reached via the generator bases) from being misread as a row source. Generator-base behaviour is unchanged.
Declaration-order sorting of the joined rows is a sensible way to match the generator's emit order.
Issue7214Tests covers both modes and the awkward cases (declared type vs value type, nullable, params collection, int[] against IEnumerable<T>).
Suggestions (non-blocking)
Array parameters aren't matched.MapTypeParameters and MapTypedRowParameters recurse only through generic named types. Run<T>(T[] values) with [Arguments<int[]>] infers nothing, and the user gets 'Could not infer'. Handling IArrayTypeSymbol and Type.IsArray (same rank, then recurse on the element type) would be cheap. If you leave it out on purpose, add a test that pins that behaviour.
Duplicated algorithm. The two ~100-line implementations differ only in the type model (ITypeSymbol vs Type). Keeping them in sync depends on comments alone. A shared parity test would help: run the same set of signatures and row types through both and compare the results. Without it, the next edit to one side can drift silently.
Matching by name.TestDataRow, CancellationToken and TypedDataSourceAttribute are matched by name plus namespace string. That is fine, but GetTypeByMetadataName or a cached well-known-types lookup would avoid repeated ToDisplayString() allocations in the generator's hot path.
Interface and base-class parameters. Only exact generic-definition matches are mapped. Run<T>(IEnumerable<T>) with a List<int> row yields nothing. The PR text implies this is deliberate, so a short comment saying so would help.
The CI run after marking ready (run 41397199726 and the AOT and Locale runs on 327d20b) failed to compile TUnit.Engine for netstandard2.0. That target has neither System.Runtime.CompilerServices.ITuple nor Type.IsSZArray. The earlier heads were drafts, so CI had skipped them. bc19256 fixes the build:
The array check now uses the name-based fallback that ReflectionGenericTypeResolver already uses on .NET Framework.
The ITuple row check is skipped on netstandard2.0. There DataSourceHelpers.IsTuple recognises only ValueTuple rows, so runtime behaviour is unchanged.
Local validation: TUnit.Engine builds for all four TFMs with 0 errors. The Bugs._7214 TestProject filter on net10.0 passes 30/30 in reflection mode. In source-generated mode 27 pass and 3 fail, and those 3 are the failures Issue7214Tests expects (ITupleRowSource and IntNullableOneElementTupleRowSource).
Dispositions for the latest Claude review (on 327d20b). None of its notes were blocking.
Parity test between the two inference implementations: not added here. The Engine tests already run every row shape in both modes and compare the test names.
Name-based matching of runtime helpers: kept, for the same reason as in earlier rounds. The generator cannot reference the runtime types.
T[] against int[]: this falls through to runtime inference, as before this PR. It is out of this issue's scope.
The sort in TryAddInstantiation is negligible at realistic sizes. The HasArgumentsArray doc comment is kept.
Review: infer method type arguments from [Arguments<T>] rows
The fix is correct in direction, and the two modes are kept consistent as AGENTS.md requires. I read the diff and did not run the tests. I found nothing blocking. These are design concerns, mostly maintainability.
What looks good
The hasGeneratorBase guard in both the generator and the reflection walk is right. DataSourceGeneratorAttribute<T> also derives from TypedDataSourceAttribute<T>, so the guard stops those sources taking the row path.
HasArgumentsArray now excludes generic attributes, so [Arguments<T[]>] is no longer read as an untyped params array.
The tests are thorough: they cover both modes, edge shapes (nullable tuples, ITuple, TestDataRow, Func, params collections) and the expected cannot-infer failures.
Concerns and suggestions
Duplicated inference logic.InferMethodTypeArgumentsFromRowType (Roslyn symbols) and InferTypesFromTypedRow (System.Reflection) are about 150 lines each and mirror each other branch for branch. Every future change to the row-binding rules needs two edits, and the doc comments already say they must stay in sync. It would be safer to have one place decide the shape of the row, for example a small classifier that returns an enum (Spread(elementTypes), Whole(type), Unknown), and to keep the two mapping layers thin. If that is too much for this PR, add a shared parity test that runs one table of (row type, method signature) cases through both implementations. The _7214 engine tests only check this indirectly.
Name-based type matching. The generator matches TestDataRow, Func, TypedDataSourceAttribute and ITuple by Name plus a namespace string, and builds ToDisplayString() namespace strings on each check. That is consistent with the surrounding code, but these checks run on the generator hot path and allocate. Prefer caching the INamedTypeSymbols from Compilation.GetTypeByMetadataName, or at least compare ContainingNamespace structurally.
Allocations in the generator.method.Parameters.Where(...).ToArray(), Count(...) and type.AllInterfaces.Any(...) run on every generic-method data source. This is minor, but incremental generators should avoid LINQ in per-method work.
Reflection-mode AOT and trimming.InferTypesFromTypedRow reads BaseType, parameters and generic arguments, which is the same reflection surface the surrounding code already uses. I did not see any new [RequiresUnreferencedCode] annotation on it. Please confirm the existing caller's annotations cover it.
Hand-rolled ordering. The join path does existingRows.Sort(...) on DeclarationIndex inside AddInstantiation. This is O(n log n) per row added, and mutating a list that the caller also holds is fragile. Inserting at the right position, or sorting once after the loop, would be cleaner.
Cost of the special cases. The nullable-tuple, ITuple and reference-array-spread rules are each correct, but each one adds a branch to both implementations. Several of them just return null to leave the row to runtime inference. Consider whether a general rule such as "any row type whose shape is not statically known infers nothing" could replace several of the branches.
Overall this is a solid fix. Merging it is reasonable, and I'd file a follow-up issue to unify the two inference implementations.
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Review comments at @src/TUnit.Engine/Discovery/ReflectionTestDataCollector.cs:
- Line 2270: Update the ITuple handling in ReflectionTestDataCollector so
netstandard2.0 rows are not closed as Run<ITuple> when their yielded values may
be spread into incompatible arguments. Detect ITuple without a compile-time
reference on that target, or leave the row for runtime inference; preserve
equivalent behavior in source-generator and engine metadata collection.
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…#7214)
netstandard2.0 cannot reference ITuple, so the typed-row check skipped it there and an ITuple row could close Run<T> as Run<ITuple> while its ValueTuple values spread. Match ITuple by name on that target, as the generator's IsITuple excludes any ITuple row in both modes.
The latest Claude review (on bc19256) found nothing blocking. Here are the dispositions. e0738cb fixes the CodeRabbit netstandard2.0 ITuple finding. I pushed back on the CodeRabbit reflection-merge finding with logged test IDs: the IDs do not collide. Both threads are resolved.
Name-based matching: kept. The generator cannot reference the runtime types, as covered in earlier rounds.
LINQ in the generator: the cost is negligible, since this runs only for generic methods with typed sources.
AOT and trimming: InferTypesFromTypedRow runs only in reflection mode, under callers that already carry the ReflectionTestDataCollector reflection annotations. AOT CI passed on bc19256.
The sort in AddInstantiation is negligible at realistic row counts, as covered in earlier rounds.
Local validation on e0738cb: TUnit.Engine builds for all four TFMs with 0 errors. The Bugs._7214 filter on net10.0 passes 30/30 in reflection mode. In source-generated mode 27 pass and 3 fail, and those 3 are the failures Issue7214Tests expects (ITupleRowSource and IntNullableOneElementTupleRowSource).
Review: typed [Arguments<T>] row inference on generic methods (#7214)
I read the generator, reflection and discovery changes. I did not build the branch or run any tests, and I did not read the new test project in detail.
Overall: The fix targets the right place. Both modes now infer method type arguments from the T of TypedDataSourceAttribute<T> rows. The change is conservative: it infers nothing (so the existing runtime path or the 'could not infer' diagnostic applies) wherever the row shape depends on runtime values. That covers object[], System.Tuple, other ITuple, nullable tuples and object arrays inside a TestDataRow. The ordering guard (hasGeneratorBase / the generator bases being reached first in the base-type walk) is correct. Excluding generic attributes from HasArgumentsArray is also correct, because [Arguments<int[]>] otherwise looks like a params array.
Concerns and suggestions
The same rules are implemented twice.InferMethodTypeArgumentsFromRowType (Roslyn symbols) and InferTypesFromTypedRow (reflection) are about 150 lines each and mirror each other branch for branch. That duplication is partly unavoidable, because the two modes read different type models. Two things would still reduce drift risk:
Add a parity test that runs the same table of row/method shapes through both modes and asserts they infer the same result. Issue7214Tests covers end-to-end behaviour but not every branch, such as T? parameters, params collections and a nested TestDataRow<Func<(..)>>.
Split the function into small steps: normalise the row (unwrap Func/TestDataRow), classify it (spread, whole or opaque), then bind. This makes the two versions line up one to one and easier to review. The single large method with a recursive self-call for a one-element tuple containing a TestDataRow is the hardest part to follow.
Argument matching is narrower than C# inference.
MapTypeParameters only recurses when the parameter and value are the same generic definition. It does not look through arrays (T[] with int[]), or through interface or base-class relationships (IEnumerable<T> with List<int>).
Failing to infer is the safe outcome, since the engine reports 'could not infer'. Still, Run<T>(T[] x) with [Arguments<int[]>] is a very natural case. Handling array element types would be a cheap addition (IArrayTypeSymbol and Type.IsArray), or the limitation could be documented.
IsParams and params-collection handling differs between the two implementations. The generator uses p.IsParams, which covers params collections in the preview language version. Reflection uses ParamArrayAttribute plus IsParamCollection. I did not check that these agree for params ReadOnlySpan<T> and params IEnumerable<T>. A parity test (see 1) would settle it.
Join semantics in reflection. The new branch in AddInstantiation re-sorts existingRows by DeclarationIndex on every insertion, which is O(n² log n) in the number of rows. That is fine for realistic counts. A sorted insertion, or one sort after all rows are collected, would be cleaner and would keep the 'rows keep declaration order' invariant in one place.
Small: the UnwrapSingleArgument name-and-namespace string checks could use Compilation.GetTypeByMetadataName types if a compilation is available. That would avoid comparing ToDisplayString() allocations on every attribute in a generator hot path. This is minor and not blocking.
No correctness bugs found in what I read. Test coverage looks thorough and the behaviour is well documented in the XML comments. I'd approve once CI is green, ideally with the parity test from (1) added.
Dispositions for the latest Claude review (on e0738cb). It found nothing blocking. Codex is clean on this head, Greptile scores it 5/5, and all CI is green.
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Summary
On a generic test method, a typed
[Arguments<T>]row was not used to infer type arguments in source-generated mode. Neither the[Arguments]row inference (HasArgumentsArrayis false forArguments<T>) nor the typed-source inference (it recognised onlyDataSourceGeneratorAttribute/AsyncDataSourceGeneratorAttributebases, andArgumentsAttribute<T>derives fromTypedDataSourceAttribute<T>) handled it. On currentmainthe row was reported as "Could not infer the type arguments" (since #7163); earlier it was silently dropped. Reflection mode ran it.Changes:
TUnit.Core.TypedDataSourceAttribute<T>with noDataSourceGeneratorAttribute/AsyncDataSourceGeneratorAttributebase, such as[Arguments<T>]) now infers the method type arguments by matchingTagainst the data parameters, excluding anyCancellationToken. The whole row binds to a single data parameter; otherwise each tuple element binds to one data parameter, with generic type arguments nested in the parameter types matched as well. Every type parameter must be inferred, each to exactly one type.[Arguments<int[]>]onRun<T>(IEnumerable<T>)therefore infers nothing, rather than an uncallableRun<int[]>. A tuple row (a one-elementValueTupleincluded) always spreads over the data parameters, asToObjectArrayspreads it before invocation; anobject[],System.Tupleor otherITuplerow (whichDataSourceHelpers.IsTuplespreads without declaring element types) infers nothing. Omitted trailing optional parameters (params arrays and params collections included) are allowed, aFunc<T>,TestDataRow<T>(or a type deriving from it) orTestDataRow<Func<T>>row binds as itsTbecause it is invoked and unwrapped before invocation (a reference-type arrayTthere is spread byUnwrapArray, so its element binds; anobjectelement type infers nothing), and aT?parameter takes a row of its underlying type. A nullable tuple row infers nothing in either mode: a non-null value boxes to the tuple and spreads, but a null one binds whole, soRun<int>would turn it into0. Reflection mode infers each such row from its value; source-generated mode reports the Source-gen silently drops a generic test method when its type arguments cannot be inferred from the data source #7163 cannot-infer failure. A typed[Arguments<T[]>]row is never read as an untyped[Arguments]params array.TypedDataSourceInference.InferMethodTypeArgumentsFromRowType.TestMetadataGenerator.InferTypesFromDataSourceAttributecalls it on generic classes too. The class-only inference path (a non-generic method of a generic class) and the generator-base rules are unchanged.InferTypesFromTypedDataSourceapplies the same rules throughInferTypesFromTypedRow. This covers both the[GenerateGenericTest]path and the declared-type path without it (Typed data source whose declared type differs from its values: source-gen closes the generic method over the declared type, reflection over the run-time type #7206), so[Arguments<object>(1)]runsRun<object>in both modes.[GenerateGenericTest], an[Arguments<T>]row whose types another source already instantiated now joins that instantiation in reflection mode, in declaration order. The generator already joined it, because its name matchesArgumentsAttribute, so both modes now run the row instead of reflection dropping it.Tests
tests/TUnit.TestProject/Bugs/_7214cases andtests/TUnit.Engine.Tests/Issue7214Tests.cs(both modes):[Arguments]with[Arguments<int>]in either order, two[Arguments<int>]rows, a generic class closed by[GenerateGenericTest], and method[GenerateGenericTest]variants, including a typed row of a different type, a declaredobjectrow onRun<T>(T), an[Arguments<int[]>]row on anIEnumerable<T>parameter, a row with a trailing optional parameter, a row on aT?parameter, a row with an omitted C# 13paramscollection, a typed source ofTestDataRow<int>rows (unwrapped toT, as at invocation), a typed source of rows of a record deriving fromTestDataRow<int>(unwrapped the same way), and typed sources ofFunc<int>andTestDataRow<Func<int>>rows (invoked toint), a typed source ofValueTuple<int>rows (spread toint), a typed source ofValueTuple<TestDataRow<int>>rows (spread, then unwrapped toint), a typed source ofTestDataRow<string[]>rows (spread tostring), a null[Arguments<string[]>]row (onlyRun<string[]>, no untypedRun<object>), and a typed source ofITuplerows (not closed asRun<ITuple>: reflection infersRun<int>from the value, and source-generated mode reports the Source-gen silently drops a generic test method when its type arguments cannot be inferred from the data source #7163 cannot-infer failure, so the class has no[EngineTest]attribute), and a typed source of non-null and nullValueTuple<int>?rows (reflection runsRun<int>(1)andRun<object>(null); source-generated mode reports cannot-infer)._7214tests in source-gen and reflection modes (30 tests: reflection 30/30; source-gen 27/27 plus the expected cannot-infer failures ofTypedITupleRowSourceand the twoTypedNullableTupleRowSourcerows), theTUnit.Core.SourceGenerator.Testssnapshots (no changes), andTUnit.Analyzers.Tests.TUnit.Engine.Testsbuilds; its run is left to CI, per AGENTS.md.Closes #7214
Summary by CodeRabbit
paramsparameters, and typed data sources.