workflowcheck crash (index out of range)

[Bysmyyr]

Expected Behavior

No crash when running with -debug=f or through golangci-lint

Actual Behavior

It crashes: (happens with other codebases too but for the simplicity, running it with this codebase)

contrib/tools/workflowcheck on  master
❯ go run main.go -debug=f ./...
panic: runtime error: index out of range [0] with length 0

goroutine 2756 [running]:
golang.org/x/tools/go/analysis/internal/checker.(*action).exportPackageFact(0xc01346ed20, {0x849a88, 0xc010375d40})
	/home/olli/go/pkg/mod/golang.org/x/tools@v0.25.0/go/analysis/internal/checker/checker.go:963 +0x309
go.temporal.io/sdk/contrib/tools/workflowcheck/determinism.(*collector).applyFacts(0xc00ca16e40)
	/home/olli/Downloads/sdk-go/contrib/tools/workflowcheck/determinism/checker.go:427 +0x3ec
go.temporal.io/sdk/contrib/tools/workflowcheck/determinism.(*Checker).Run(0xc0000b51c0, 0xc0057ea460)
	/home/olli/Downloads/sdk-go/contrib/tools/workflowcheck/determinism/checker.go:202 +0x646
go.temporal.io/sdk/contrib/tools/workflowcheck/workflow.(*Checker).Run(0xc0000906c0, 0xc0057ea460)
	/home/olli/Downloads/sdk-go/contrib/tools/workflowcheck/workflow/checker.go:157 +0x117
go.temporal.io/sdk/contrib/tools/workflowcheck/workflow.(*Checker).NewAnalyzer.func1(0x7fffc5da3579?)
	/home/olli/Downloads/sdk-go/contrib/tools/workflowcheck/workflow/checker.go:129 +0x1d
golang.org/x/tools/go/analysis/internal/checker.(*action).execOnce(0xc01346ed20)
	/home/olli/go/pkg/mod/golang.org/x/tools@v0.25.0/go/analysis/internal/checker/checker.go:759 +0xad0
sync.(*Once).doSlow(0xc006b70030?, 0xc007fb04b0?)
	/home/olli/go/go1.24.1/src/sync/once.go:78 +0xab
sync.(*Once).Do(...)
	/home/olli/go/go1.24.1/src/sync/once.go:69
golang.org/x/tools/go/analysis/internal/checker.(*action).exec(...)
	/home/olli/go/pkg/mod/golang.org/x/tools@v0.25.0/go/analysis/internal/checker/checker.go:666
golang.org/x/tools/go/analysis/internal/checker.execAll.func1(0x0?)
	/home/olli/go/pkg/mod/golang.org/x/tools@v0.25.0/go/analysis/internal/checker/checker.go:654 +0x3b
created by golang.org/x/tools/go/analysis/internal/checker.execAll in goroutine 2747
	/home/olli/go/pkg/mod/golang.org/x/tools@v0.25.0/go/analysis/internal/checker/checker.go:660 +0x191
exit status 2

We found the issue when integrating the check for golangci-lint. With golangci-lint it crash always.

golangCI-lint has its own pass which does this always:

    act.Err = errorutil.NewPanicError(fmt.Sprintf("%s: package %q (isInitialPkg: %t, needAnalyzeSource: %t): %s",
       act.Analyzer.Name, act.Package.Name, act.isInitialPkg, act.needAnalyzeSource, p), debug.Stack())
}

when run on its own, it uses go standard reporter which does that only when debug flag is on, with it it fails:

if dbg('f') {
    fmt.Fprintf(os.Stderr, "%s: package %s has fact %s\n",
       act.pkg.Fset.Position(act.pass.Files[0].Pos()), act.pass.Pkg.Path(), fact)
}

Somehow the act.pass.Files is empty slice. In this case the key is package unsafe ("unsafe").

Steps to Reproduce the Problem

1. cd contrib/tools/workflowcheck
2. go run main.go -debug=f ./...

Specifications

• Version: master (b9afba9)
• Platform: go version go1.24.1 linux/amd64

[cretz]

Looks like this may be a bug in the Golang repo on code that assumes a file is present in that slice (and still exists despite being moved to https://github.com/golang/tools/blob/3e7f74d009150bf5e66483f3759d8c59f50e873d/go/analysis/checker/checker.go#L591).