golang/go · error

import path contains control character: %q

Error message

import path contains control character: %q

What it means

Returned by checkImportPath when a rune in the path is a C0 control character (r < 0x20) or DEL (0x7f). Import paths may not contain control characters because they are not portable across filesystems, shells, or version control.

Source

Thrown at src/cmd/compile/internal/noder/import.go:322

		return errors.New("import path is empty")
	}

	if strings.Contains(path, "\x00") {
		return errors.New("import path contains NUL")
	}

	for ri := range base.ReservedImports {
		if path == ri {
			return fmt.Errorf("import path %q is reserved and cannot be used", path)
		}
	}

	for _, r := range path {
		switch {
		case r == utf8.RuneError:
			return fmt.Errorf("import path contains invalid UTF-8 sequence: %q", path)
		case r < 0x20 || r == 0x7f:
			return fmt.Errorf("import path contains control character: %q", path)
		case r == '\\':
			return fmt.Errorf("import path contains backslash; use slash: %q", path)
		case !allowSpace && unicode.IsSpace(r):
			return fmt.Errorf("import path contains space character: %q", path)
		case strings.ContainsRune("!\"#$%&'()*,:;<=>?[]^`{|}", r):
			return fmt.Errorf("import path contains invalid character '%c': %q", r, path)
		}
	}

	return nil
}

View on GitHub (pinned to b6b368adc5)

Solutions

1. Inspect the import line for invisible characters (cat -A or your editor's show-whitespace).
2. Retype the import path removing all control bytes.
3. Generate import paths from trusted identifiers only.

for _, r := range path {
    if r < 0x20 || r == 0x7f {
        return fmt.Errorf("control character in import path")
    }
}

When it happens

Trigger: An import path literal contains a tab, newline, NUL (already guarded separately), backspace, ESC, or DEL; the switch fires the r < 0x20 || r == 0x7f case.

Common situations: A multi-line import accidentally containing a literal newline/tab, terminal copy-paste inserting control bytes, or a generated import with embedded formatting characters.

Related errors

• import path %q is reserved and cannot be used
• import path contains invalid UTF-8 sequence: %q
• import path contains backslash; use slash: %q
• import path contains space character: %q
• import path contains invalid character '%c': %q

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/64bad022f1e77abc. Report an issue: GitHub.