gohugoio/hugo · error

failed to compile ignoreFiles pattern

Error message

failed to compile ignoreFiles pattern %q: %s

What it means

Returned by CompileConfig when compiling the `ignoreFiles` regex patterns fails. Each pattern is compiled with regexp.Compile; a syntax error in any pattern aborts config compilation and names the offending pattern plus the regexp error.

Solutions

1. Test each pattern with a Go regexp playground or `go run -` using regexp.Compile.
2. Use RE2-compatible syntax; remove look-ahead/look-behind and backreferences.
3. Double-escape backslashes in TOML (`\\.` not `\.`) and verify in YAML/JSON accordingly.
4. Remove patterns one by one to isolate the bad one.

Example fix

// before
ignoreFiles = ["\\.draft("]
// after
ignoreFiles = ["\\.draft$"]

func compileIgnoreFiles(patterns []string) error {
  for _, p := range patterns { if _, err := regexp.Compile(p); err != nil { return fmt.Errorf("bad ignoreFiles pattern %q: %w", p, err) } }
  return nil
}

When it happens

Trigger: Setting `ignoreFiles = ["\\.foo(", "[a-"]"]` or any PCRE/Go-re2 syntax error: unbalanced parentheses, malformed character classes, unsupported look-ahead (re2 has none), or stray backslashes.

Common situations: Porting ignore patterns from JavaScript/PCRE regex dialects into Hugo (which uses Go's RE2 engine), unescaped backslashes in TOML strings, or trailing partial patterns from manual edits.

Related errors

• failed to compile cache buster target
• failed to compile whitelist pattern
• failed to parse clock
• failed to parse timeout
• invalid deployment.matchers.pattern

AI-assisted analysis of gohugoio/hugo@52c9bd7908 (2026-08-09). Data as JSON: /api/errors/66e7e0753acad34d. Report an issue: GitHub.

Appendix: source

Thrown at config/allconfig/allconfig.go:375

		case bool:
			return v
		case map[string]bool:
			return v[section]
		default:
			return false
		}
	}

	ignoreFile := func(s string) bool {
		return false
	}
	if len(c.IgnoreFiles) > 0 {
		regexps := make([]*regexp.Regexp, len(c.IgnoreFiles))
		for i, pattern := range c.IgnoreFiles {
			var err error
			regexps[i], err = regexp.Compile(pattern)
			if err != nil {
				return fmt.Errorf("failed to compile ignoreFiles pattern %q: %s", pattern, err)
			}
		}
		ignoreFile = func(s string) bool {
			for _, r := range regexps {
				if r.MatchString(s) {
					return true
				}
			}
			return false
		}
	}

	var clock time.Time
	if c.Internal.Clock != "" {
		var err error
		clock, err = time.Parse(time.RFC3339, c.Internal.Clock)
		if err != nil {
			return fmt.Errorf("failed to parse clock: %s", err)

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