Swift extractor: lazy declaration TRAP file name exceeds 255 bytes for C++ template specializations #22843

Description of the issue

The Swift extractor fails to write the TRAP file for a lazily extracted declaration when the declaration's name is a long C++ template specialization. The file name exceeds the 255-byte limit on macOS, so opening it fails with ENAMETOOLONG and the extractor reports an internal error.

Assertion failed: `(*__error()) == 17`. Unable to open /Users/runner/work/_temp/codeql_databases/swift/trap/swift/lazy_decls/__ObjC/Struct_optional<std.__1.variant<margelo.nitro.NullType, std.__1.vector<std.__1.basic_string<CChar, std.__1.char_traits<CChar>, std.__1.allocator<CChar>>, std.__1.allocator<std.__1.basic_string<CChar, std.__1.char_traits<CChar>, std.__1.allocator<CChar>>>>>>_496c496d2da3e26471a167a87ade75de.trap for writing (system:63)

Some or all of the Swift analysis may have failed.

The type is std::optional<std::variant<NullType, std::vector<std::string>>>, generated by Nitro Modules and imported through Swift/C++ interop. The job itself succeeds and the SARIF uploads; only this declaration is missing from the database.

Cause

mangledDeclName in swift/extractor/SwiftExtractor.cpp already hashes the mangled name because it "can be too long for file names", but it still appends the full userFacingName() before the hash. For a C++ template specialization that readable part alone can be longer than 255 bytes. getRelativeTrapPath in swift/extractor/infra/TargetDomains.cpp then uses the result as the file name unchanged.

A possible fix is to cap the readable part (for example, to a few dozen bytes) before appending the hash, so the hash keeps names unique.

Environment

• CodeQL CLI 2.27.2, github/codeql-action v4 (24c54180a607b1449ed407dd24f251e4e9147c8d)
• GitHub-hosted macOS runner, build-mode: manual, Swift analysis of a React Native library with Nitro Modules
• Public reproduction: job log from hyodotdev/openiap (libraries/react-native-iap). It reproduces on every run of that job.