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TestDataAnalyzer: detect Func<T> by symbol instead of display-string prefix #7380
Description
TestDataAnalyzer detects Func<T> by calling ToDisplayString().StartsWith("System.Func<", StringComparison.Ordinal). This allocates a display string during analysis and relies on formatting instead of symbol identity.
Current code
Following merged PR #7347 (#7227), the three checks are:
- Two property-injection checks in
src/TUnit.Analyzers/TestDataAnalyzer.cs, usingfuncTypeandfuncTypeForError. TryUnwrapFuncin the same file, called while peeling the supported data-row wrappers.
Both automated reviewers raised this as non-blocking on #7347 (review comment). That prerequisite has merged; this issue is available for implementation.
Acceptance criteria
- Resolve
System.Func`1once per compilation withCompilation.GetTypeByMetadataName("System.Func`1"). - Compare
OriginalDefinitionwithSymbolEqualityComparer.Defaultin all three checks, as the analyzer already does forTestDataRow<T>. - Preserve the existing wrapper-peeling order and property-injection behavior.
- Add analyzer cases for
Func<TestDataRow<(int, int)>>andTestDataRow<Func<(int, int)>>against an(int a, int b)test signature. These are regression coverage for the existing tuple expansion after wrapper peeling; there is no known defect in that ordering. - Run the relevant
TUnit.Analyzers.Testscoverage.
Activity
thomhurst commentedon Nov 2, 2026
Triage update: #7347 has merged and #7227 is closed.
TryUnwrapFuncis now onorigin/mainand still uses the display-string prefix, as do both property-injection checks. Removed the completed prerequisite link and incorporated the tuple-wrapper regression cases into the acceptance criteria.thomhurst commentedon Nov 2, 2026
An extra item from the Claude review of #7347 (comment 6570666000), to cover alongside the symbol-based
Func<T>match: add analyzer tests for tuples inside the wrappers, for exampleFunc<TestDataRow<(int, int)>>andTestDataRow<Func<(int, int)>>against a(int a, int b)test signature.UnwrapTypesstill runs its tuple expansion after the fixed Func → TestDataRow → Func peel, so there is no known defect. The tests would lock that ordering in, and changingTryUnwrapFuncwould touch the same path.