panic: nil pointer dereference in CreateDiagnosticForNodeInSourceFile for a malformed "files" array in tsconfig.json #65079

🔎 Search Terms

panic, nil pointer dereference, tsconfig, files, TS18002, CreateDiagnosticForNodeInSourceFile, parseJsonConfigFileContentWorker

🕗 Version & Regression Information

Crashes in 7.0.2 and in 7.1.0-dev.20261031.1 (main at 6161772). TypeScript 6.0.3 does not crash.

💻 Code

// tsconfig.json
{"files":[}]}

Run tsc -p tsconfig.json.

🙁 Actual behavior

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=...]

goroutine 1 [running]:
github.com/microsoft/TypeScript/tsc/internal/tsoptions.CreateDiagnosticForNodeInSourceFile(..., 0x0, ...)
	tsc/internal/tsoptions/errors.go:93
github.com/microsoft/TypeScript/tsc/internal/tsoptions.parseJsonConfigFileContentWorker(...)
	tsc/internal/tsoptions/tsconfigparsing.go:1200
github.com/microsoft/TypeScript/tsc/internal/tsoptions.ParseJsonSourceFileConfigFileContent(...)
	tsc/internal/tsoptions/tsconfigparsing.go:650

🙂 Expected behavior

The same as TypeScript 6.0.3, which exits 2 with:

error TS18002: The 'files' list in config file '<dir>/tsconfig.json' is empty.
tsconfig.json(1,1): error TS5092: The root value of a 'tsconfig.json' file must be an object.
tsconfig.json(1,11): error TS1137: Expression or comma expected.
tsconfig.json(1,12): error TS1012: Unexpected token.

Additional information about the issue

In the "files list is empty" branch (tsconfigparsing.go:1190-1200), ForEachTsConfigPropArray(sourceFile.SourceFile, "files", ...) returns nil for this malformed JSON, and CreateDiagnosticForNodeInSourceFile dereferences the nil node (errors.go:93). TypeScript 6.0.3 calls createDiagnosticForNodeInSourceFileOrCompilerDiagnostic at this spot, which falls back to a global diagnostic; that's why its TS18002 has no location. The Go equivalent, CreateDiagnosticForNodeInSourceFileOrCompilerDiagnostic, already exists (errors.go:90), so the fix is probably to call it here.

Found by differential fuzzing.