Preserve test.method classification across multiline C# attribute blocks

[Widthdom]

Summary

A C# method decorated with [Theory] is classified as function instead of test.method when following [InlineData(...)] attributes span multiple physical lines or contain complex literals.

The method declaration and range are extracted correctly, but the test classifier walks attributes one physical line at a time and stops at a continuation line that does not begin with [. This is a residual of #1961, which introduced the test.method distinction.

Environment

• origin/main: c642bc4c3dda4ef659df8e6b699e10f61da3c836
• cdidx v1.44.3, locally built
• fresh repository-wide index
• full net8.0 and net9.0 suites pass

Reproduction

dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll symbols \
  --name SymbolIdentity_NonCSharpBroadAmbiguityDoesNotPersistCrossProductOrAttributeCallers \
  --lang csharp \
  --path tests/CodeIndex.Tests/DbReaderSymbolIdentityTests.cs \
  --db .cdidx/codeindex.db --json=array

dotnet ./src/CodeIndex/bin/Debug/net8.0/cdidx.dll symbols \
  --name GetUnusedSymbols_MultilineAttributeLiteralWithBracketInString_KeepsReflectionContext \
  --lang csharp --path tests/CodeIndex.Tests/DbReaderTests.cs \
  --db .cdidx/codeindex.db --json=array

The first method has [Theory] at line 538, multiline InlineData blocks through line 550, and its declaration at line 551. The second has [Theory] at line 7797, complex multiline attributes through line 7814, and its declaration at line 7815.

Both rows currently return:

{"kind":"function"}

Nearby simple [Fact] and [Theory] methods remain test.method.

Expected behavior

Both methods are xUnit theories and must be emitted as test.method. Classification must survive a contiguous attribute block regardless of physical line breaks or bracket-like content inside correctly lexed literals/comments.

Root cause

IsCSharpTestMethod in src/CodeIndex/Indexer/Symbols/SymbolExtractor.DeclarationMetadata.cs:122 walks backward by physical line. Each preceding line must begin with [ and contain ] on the same line. A continuation such as a string argument terminates the scan before it reaches [Theory].

CSharpLineHasTestMethodAttribute is also physical-line-oriented and cannot represent one multiline attribute list as a lexical unit.

Focused PR scope

One PR should replace the line-only backward scan with a bounded, lexical, attribute-block-aware classifier while preserving the existing C# test-attribute taxonomy.

Non-goals

• Do not add a Roslyn dependency.
• Do not redesign symbol kinds or infer tests from method names alone.
• Do not broaden this PR to non-C# frameworks/languages.
• Do not parse arbitrary attribute constructor semantics.

Implementation guidance and cautions

• Reuse existing C# lexical/string/comment machinery where practical.
• Balance complete attribute blocks, ignoring brackets, commas, quotes, and comment markers inside normal, verbatim, raw, interpolated, and character literals.
• Keep line/character/item budgets explicit.
• Stop at real declaration/member boundaries and prevent a prior member's [Theory] leaking forward.
• Preserve target-specified attributes such as return:, assembly:, and module: without treating them as method test markers.
• Continue recognizing namespaced and Attribute-suffixed forms already supported.

Required tests

• One and several multiline InlineData attributes.
• Attributes split across brackets, parentheses, and argument lines.
• Comments between attributes.
• Namespaced Xunit.TheoryAttribute.
• Normal, verbatim, raw, and interpolated strings containing brackets and triple-quote runs.
• Same-line multiple attributes and non-test multiline attributes.
• Member boundaries that prevent marker leakage.
• Existing Fact, Theory, MSTest, and NUnit variants.

Assert outline, symbols --kind test.method, inspect, and exclude-tests/unused behavior.

Acceptance criteria

• The methods at lines 551 and 7815 are emitted as test.method.
• Existing simple classifications remain correct.
• Complex literals do not create phantom attributes.
• Attribute ownership never crosses a member boundary.
• The scan remains bounded.

Regression history

• Test method kind not distinguished from functions #1961 explicitly introduced test.method and required parameterized/preceding-line decorators.
• C# attribute bracket-aware strip is single-line only — multi-line verbatim/raw strings still leak reflection context across declarations #409 is adjacent complex attribute/string lexing history.

This is a direct residual of #1961 and should be referenced in regression tests and the bilingual changelog. No newer exact issue was found.