vitessio/vitess · error

malformatted golang image reference: %s

Error message

malformatted golang image reference: %s

What it means

go-upgrade rewrites golang Docker image references in files (e.g. Dockerfiles/workflows) using golangImageRegexp, which expects 3 capture groups (prefix, distro, and the full match context). If a matched image reference doesn't conform to the expected `golang:<tag>` shape, replaceErr is set to this error and the match is left unchanged.

Source

Thrown at go/tools/go-upgrade/go-upgrade.go:493

		}

		digest, err := resolveGolangImageDigest(goVersion, distro)
		if err != nil {
			return "", err
		}

		digestsByDistro[distro] = digest
	}

	var replaceErr error
	replaced := golangImageRegexp.ReplaceAllStringFunc(content, func(match string) string {
		if replaceErr != nil {
			return match
		}

		submatch := golangImageRegexp.FindStringSubmatch(match)
		if len(submatch) != 3 {
			replaceErr = fmt.Errorf("malformatted golang image reference: %s", match)
			return match
		}

		prefix := submatch[1]
		distro := submatch[2]
		digest, ok := digestsByDistro[distro]
		if !ok {
			replaceErr = fmt.Errorf("missing golang digest for distro %s", distro)
			return match
		}

		return fmt.Sprintf("%s%s@%s", prefix, golangDockerTag(goVersion, distro), digest)
	})
	if replaceErr != nil {
		return "", replaceErr
	}

	return replaced, nil

View on GitHub (pinned to 01a25a7d17)

Solutions

1. Find the file containing the malformed image reference reported by the error and normalize it to the standard `golang:<version>-<distro>` form
2. If a new legitimate format exists (new registry/distro), extend golangImageRegexp to capture it
3. Avoid hand-editing image lines; let go-upgrade rewrite them
4. Re-run go-upgrade to confirm all references are replaced

Example fix

// before (Dockerfile)
FROM golang:1.22-custombuild
// after
FROM golang:1.22-bookworm

re := regexp.MustCompile(`golang:\d+\.\d+(\.\d+)?-[a-z0-9]+`)
for _, line := range dockerfileLines {
    if strings.Contains(line, "golang:") && !re.MatchString(line) {
        return fmt.Errorf("normalize image line %q to 'golang:<version>-<distro>' before running go-upgrade", line)
    }
}

func isCanonicalGolangRef(ref string) bool {
    return golangImageRegexp.MatchString(ref) && len(golangImageRegexp.FindStringSubmatch(ref)) == 3
}

if err := upgrade.replaceGolangImageReferences(...); err != nil {
    if strings.Contains(err.Error(), "malformatted golang image") {
        return fmt.Errorf("hand-edited image line detected; restore canonical form: %w", err)
    }
    return err
}

When it happens

Trigger: A file contains a string matched loosely by the image-reference regex but not in the canonical form, e.g. `golang:1.22` with an unexpected suffix, a custom registry form the regex groups differently, or a hand-edited image line like `FROM myrepo/golang:1.22-bookworm-custom` that yields fewer than 3 submatches.

Common situations: Hand-editing a Dockerfile or CI workflow image line; adding a new distro tag format not anticipated by the regex; using a private registry mirror whose reference shape differs from the standard golang image.

Related errors

• missing golang digest for distro %s
• malformatted error, got: %v
• golang version malformatted: %s
• resolve golang digest for %s: %w
• package %s is not under %s

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/ad2342ace56c56ae. Report an issue: GitHub.