golang/go · error

unknown condition %q

Error message

unknown condition %q

What it means

Thrown by Engine.conditionsActive when a condition bracket has no colon but the tag is not in e.Conds (engine.go:527-530). Unlike the prefix variant this message does not list known conditions. It means the bare condition name was never registered.

Source

Thrown at src/cmd/internal/script/engine.go:529

	return b.String()
}

func (e *Engine) conditionsActive(s *State, conds []condition) (bool, error) {
	for _, cond := range conds {
		var impl Cond
		prefix, suffix, ok := strings.Cut(cond.tag, ":")
		if ok {
			impl = e.Conds[prefix]
			if impl == nil {
				return false, fmt.Errorf("unknown condition prefix %q; known: %v", prefix, slices.Collect(maps.Keys(e.Conds)))
			}
			if !impl.Usage().Prefix {
				return false, fmt.Errorf("condition %q cannot be used with a suffix", prefix)
			}
		} else {
			impl = e.Conds[cond.tag]
			if impl == nil {
				return false, fmt.Errorf("unknown condition %q", cond.tag)
			}
			if impl.Usage().Prefix {
				return false, fmt.Errorf("condition %q requires a suffix", cond.tag)
			}
		}
		active, err := impl.Eval(s, suffix)

		if err != nil {
			return false, fmt.Errorf("evaluating condition %q: %w", cond.tag, err)
		}
		if active != cond.want {
			return false, nil
		}
	}

	return true, nil
}

View on GitHub (pinned to b6b368adc5)

Solutions

1. Check spelling and case against the registered condition names (conditions are case-sensitive).
2. Ensure DefaultConds() and any needed AddToolChainScriptConditions populate e.Conds.
3. Register the custom condition under the exact tag used in the bracket.

Example fix

// before
[CGO] exec go build
// after
[cgo] exec go build

func condKnown(conds map[string]script.Cond, tag string) bool {
    _, ok := conds[tag]
    return ok
}

When it happens

Trigger: Writing [unknowntag] cmd where unknowntag is not a key in e.Conds; using [CGO] (wrong case — conditions are case-sensitive) instead of [cgo]; referencing an unregistered custom condition.

Common situations: Case mismatch (CGO vs cgo); typo; condition not registered because AddToolChainScriptConditions or DefaultConds was not called; condition exists only in a different engine configuration.

Related errors

• unrecognized GOOS %q
• unrecognized GOARCH %q
• unrecognized compiler %q
• unknown condition prefix %q; known: %v
• condition %q cannot be used with a suffix

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/8a3e49c83376b6cd. Report an issue: GitHub.