nektos/act · error

invalid Pattern '%s': %s

Error message

invalid Pattern '%s': %s

What it means

Returned by PatternToRegex (pkg/workflowpattern/workflow_pattern.go) when the branch/path filter pattern contains syntax errors. The translator walks the pattern (handling *, **, +, ?, [...], backslash escapes) collecting per-position errors in a map, then aggregates them as 'invalid Pattern ...: Position N Error: ...' before regex compilation.

Source

Thrown at pkg/workflowpattern/workflow_pattern.go:132

				pos++
				break
			}
			rpattern.WriteString(regexp.QuoteMeta(string([]byte{pattern[pos+1]})))
			pos += 2
		default:
			rpattern.WriteString(regexp.QuoteMeta(string([]byte{pattern[pos]})))
			pos++
		}
	}
	if len(errors) > 0 {
		var errorMessage strings.Builder
		for position, err := range errors {
			if errorMessage.Len() > 0 {
				errorMessage.WriteString(", ")
			}
			errorMessage.WriteString(fmt.Sprintf("Position: %d Error: %s", position, err))
		}
		return "", fmt.Errorf("invalid Pattern '%s': %s", pattern, errorMessage.String())
	}
	rpattern.WriteString("$")
	return rpattern.String(), nil
}

func CompilePatterns(patterns ...string) ([]*WorkflowPattern, error) {
	ret := []*WorkflowPattern{}
	for _, pattern := range patterns {
		cp, err := CompilePattern(pattern)
		if err != nil {
			return nil, err
		}
		ret = append(ret, cp)
	}
	return ret, nil
}

// returns true if the workflow should be skipped paths/branches

View on GitHub (pinned to 4f41128141)

Solutions

1. Read each 'Position: N' in the message to find the exact offending character
2. Close unclosed brackets, avoid empty [] and out-of-order ranges, remove the trailing backslash
3. Use only supported glob syntax: *, **, ?, +, [a-z]-style classes, and \ to escape a literal character
4. Test patterns with CompilePattern in a scratch Go test before deploying

Example fix

# before:
branches: [main, release-[a-z}
# after:
branches: [main, 'release-[a-z]']

// Pre-validate branch/path filter patterns at config load time:
if _, err := workflowpattern.CompilePatterns("main", "release-[0-9]*"); err != nil {
    log.Fatalf("bad filter pattern: %v", err)
}

Return the error up to config loading; print the Position markers and reject the workflow file — never ignore.

When it happens

Trigger: Specific bad constructs: empty brackets '[]' (line 69), invalid character ranges in brackets like [z-a] or non A-z/0-9 chars (lines 81-97), missing closing ']' (line 106), or a trailing backslash with nothing to escape (line 113). Used for `on: push: branches:/paths:` filters.

Common situations: Writing glob patterns with shell-style ranges that contain invalid chars, forgetting to close a bracket, ending a pattern with a lone backslash, or copying regex syntax (e.g. \d, +) that the glob translator treats literally or rejects.

Related errors

• %s is not a valid mac address
• invalid value: %d. Valid memory swappiness range is 0-100
• invalid range format for --expose: %w
• invalid logging opts for driver %s
• invalid --security-opt: %q

AI-assisted analysis of nektos/act@4f41128141 (2026-08-15). Data as JSON: /api/errors/6d47d9c0747b4dfa. Report an issue: GitHub.