nodejs/node · error

%s: unsupported --formatVersion %s\n

Error message

%s: unsupported --formatVersion %s\n

What it means

genrb rejected the value passed to --formatVersion. The argument must be exactly one character and that character must be a digit between '1' and '3' (inclusive). The check uses uprv_strlen(s) != 1 together with the range test s[0] < '1' || '3' < s[0], so empty strings, multi-character strings, letters, '0', and '4'+'9' all fail. The flag merely sets illegalArg=true and does not exit immediately; the program continues argument validation and later prints the full usage text before returning U_ILLEGAL_ARGUMENT_ERROR.

Source

Thrown at deps/icu-small/source/tools/genrb/genrb.cpp:167

    /* error handling, printing usage message */
    if(argc<0) {
        fprintf(stderr, "%s: error in command line argument \"%s\"\n", argv[0], argv[-argc]);
        illegalArg = true;
    } else if(argc<2) {
        illegalArg = true;
    }
    if(options[WRITE_POOL_BUNDLE].doesOccur && options[USE_POOL_BUNDLE].doesOccur) {
        fprintf(stderr, "%s: cannot combine --writePoolBundle and --usePoolBundle\n", argv[0]);
        illegalArg = true;
    }
    if (options[ICU4X_MODE].doesOccur && !options[UCADATA].doesOccur) {
        fprintf(stderr, "%s: --icu4xMode requires --ucadata\n", argv[0]);
        illegalArg = true;
    }
    if(options[FORMAT_VERSION].doesOccur) {
        const char *s = options[FORMAT_VERSION].value;
        if(uprv_strlen(s) != 1 || (s[0] < '1' || '3' < s[0])) {
            fprintf(stderr, "%s: unsupported --formatVersion %s\n", argv[0], s);
            illegalArg = true;
        } else if(s[0] == '1' &&
                  (options[WRITE_POOL_BUNDLE].doesOccur || options[USE_POOL_BUNDLE].doesOccur)
        ) {
            fprintf(stderr, "%s: cannot combine --formatVersion 1 with --writePoolBundle or --usePoolBundle\n", argv[0]);
            illegalArg = true;
        } else {
            setFormatVersion(s[0] - '0');
        }
    }

    if((options[JAVA_PACKAGE].doesOccur || options[BUNDLE_NAME].doesOccur) &&
            !options[WRITE_JAVA].doesOccur) {
        fprintf(stderr,
                "%s error: command line argument --java-package or --bundle-name "
                "without --write-java\n",
                argv[0]);
        illegalArg = true;

View on GitHub (pinned to 1b2de5e052)

Solutions

  1. Pass a single digit 1, 2, or 3: `genrb --formatVersion 2 root.txt`.
  2. If you need the newest format, omit --formatVersion entirely so genrb uses its default (currently formatVersion 3).
  3. Check that the shell variable supplying the value is set and contains exactly one character before invoking genrb.

Example fix

// before
genrb --formatVersion 1.0 root.txt
// after
genrb --formatVersion 1 root.txt
Defensive patterns

Strategy: validation

Validate before calling

# Validate --formatVersion before invoking genrb
fv="${FORMAT_VERSION:-}"
if [ -n "$fv" ] && ! printf '%s' "$fv" | grep -qE '^[1-3]$'; then
  echo "ERROR: --formatVersion must be a single digit 1-3, got '$fv'" >&2
  exit 2
fi
genrb ${fv:+--formatVersion "$fv"} root.txt

Prevention

When it happens

Trigger: Invoking genrb with --formatVersion 0, --formatVersion 4, --formatVersion 12, --formatVersion v2, or --formatVersion with no value. Reproduce: `genrb --formatVersion 4 root.txt`. The branch at genrb.cpp:166 fires whenever the value is not a single digit in [1,3].

Common situations: Typing the version with extra characters (e.g. '1.0' or 'v3'), copying a formatVersion from documentation that targets a newer ICU where higher versions exist, or passing the flag through a build variable that resolved to empty. Often seen when scripts interpolate an unbound variable.

Related errors

AI-assisted analysis of nodejs/node@1b2de5e052 (2026-08-13). Data as JSON: /api/errors/cc7ec27409fed1f1. Report an issue: GitHub.