golang/go · error

internal error: unable to locate build action for package %q

Error message

internal error: unable to locate build action for package %q run action

What it means

BuildActionCoverMetaFile walks the run-action's dependency graph to find the matching 'build' action for the package under test, in order to locate the coverage meta-data file. If no predecessor build action has the same ImportPath, this internal error is returned. It indicates the action graph wasn't constructed as expected for 'go test -cover'.

Source

Thrown at src/cmd/go/internal/work/cover.go:75

			if cfg.BuildN {
				return metaFile, nil
			}
			f, err := os.Open(metaFile)
			if err != nil {
				return "", err
			}
			defer f.Close()
			fi, err2 := f.Stat()
			if err2 != nil {
				return "", err2
			}
			if fi.Size() == 0 {
				return "", nil
			}
			return metaFile, nil
		}
	}
	return "", fmt.Errorf("internal error: unable to locate build action for package %q run action", p.ImportPath)
}

// WriteCoveragePercent writes out to the writer 'w' a "percent
// statements covered" for the package whose test-run action is
// 'runAct', based on the meta-data file 'mf'. This helper is used in
// cases where a user runs "go test -cover" on a package that has
// functions but no tests; in the normal case (package has tests)
// the percentage is written by the test binary when it runs.
func WriteCoveragePercent(b *Builder, runAct *Action, mf string, w io.Writer) error {
	dir := filepath.Dir(mf)
	output, cerr := b.CovData(runAct, "percent", "-i", dir)
	if cerr != nil {
		return b.Shell(runAct).reportCmd("", "", output, cerr)
	}
	_, werr := w.Write(output)
	return werr
}

View on GitHub (pinned to b6b368adc5)

Solutions

1. Update to the latest patch release of Go — this is typically a toolchain bug, not user error.
2. Simplify the -coverpkg pattern to see if a specific dependency shape triggers it.
3. Run 'go test -cover ./...' instead of narrow patterns to see if the issue is pattern-specific.
4. File a Go issue with the package layout and exact go test invocation.

Example fix

// before
$ go test -coverpkg=./... -cover ./...
// error: internal error: unable to locate build action for package "example.com/m" run action

// after — update toolchain and simplify
$ go1.23.x test -cover ./...   # use latest patch
# if persists: report at https://go.dev/issue with reproduction

When it happens

Trigger: Invoked during 'go test -cover' (especially with functions but no tests, or with -coverpkg) when the run action's barrier dependency has no build predecessor matching the package's ImportPath. Should be unreachable for well-formed graphs; indicates a regression in action-graph construction.

Common situations: A Go toolchain regression in coverage action wiring; an edge case with empty packages, test-only packages, or unusual -coverpkg combinations; running a patched go command.

Related errors

• marshal MetaFileCollection: %v
• writing metafiles file: %v
• import cycle not allowed in test
• multiple definitions of TestMain
• valid modes are "set", "count", or "atomic"

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/d7809e7f6991598c. Report an issue: GitHub.