nodejs/node · error

U_ILLEGAL_ARGUMENT_ERROR

U_ILLEGAL_ARGUMENT_ERROR

Error message

Invalid option for --mode (must be uprops)

What it means

icuexportdata validates its --mode option and only accepts the value 'uprops' (Unicode property data export). Any other value for --mode produces U_ILLEGAL_ARGUMENT_ERROR. This tool has been narrowed to a single export mode; the check is a strict string comparison against 'uprops'. The tool returns the error code without exiting, so the calling process can handle it.

Source

Thrown at deps/icu-small/source/tools/icuexportdata/icuexportdata.cpp:1157

            "\tdump Unicode property data to .toml files\n"
            "options:\n"
            "\t-h or -? or --help  this usage text\n"
            "\t-V or --version     show a version message\n"
            "\t-m or --mode        mode: currently only 'uprops', but more may be added\n"
            "\t      --trie-type   set the trie type (small or fast, default small)\n"
            "\t-d or --destdir     destination directory, followed by the path\n"
            "\t      --all         write out all properties known to icuexportdata\n"
            "\t      --index       write an _index.toml summarizing all data exported\n"
            "\t-c or --copyright   include a copyright notice\n"
            "\t-v or --verbose     Turn on verbose output\n"
            "\t-q or --quiet       do not display warnings and progress\n",
            argv[0]);
        return argc<0 ? U_ILLEGAL_ARGUMENT_ERROR : U_ZERO_ERROR;
    }

    const char* mode = options[OPT_MODE].value;
    if (uprv_strcmp(mode, "uprops") != 0) {
        fprintf(stderr, "Invalid option for --mode (must be uprops)\n");
        return U_ILLEGAL_ARGUMENT_ERROR;
    }

    if (options[OPT_TRIE_TYPE].doesOccur) {
        if (uprv_strcmp(options[OPT_TRIE_TYPE].value, "fast") == 0) {
            trieType = UCPTRIE_TYPE_FAST;
        } else if (uprv_strcmp(options[OPT_TRIE_TYPE].value, "small") == 0) {
            trieType = UCPTRIE_TYPE_SMALL;
        } else {
            fprintf(stderr, "Invalid option for --trie-type (must be small or fast)\n");
            return U_ILLEGAL_ARGUMENT_ERROR;
        }
    }

    for (const char* propName : propNames) {
        UProperty propEnum = u_getPropertyEnum(propName);
        if (propEnum == UCHAR_INVALID_CODE) {
            std::cerr << "Error: Invalid property alias: " << propName << std::endl;

View on GitHub (pinned to 1b2de5e052)

Solutions

1. Use --mode uprops (the only supported value): `icuexportdata --mode uprops -d output/`
2. Omit the --mode option entirely if the default is uprops
3. Check the tool's help output for current valid options: `icuexportdata --help`
4. Update any scripts or documentation that reference deprecated mode values

Example fix

// before: invalid mode
icuexportdata --mode coll -d output/
// after: valid mode
icuexportdata --mode uprops -d output/
// or simply omit --mode
icuexportdata -d output/

# Validate icuexportdata mode before running
MODE="uprops"
[ "$MODE" = "uprops" ] || { echo "ERROR: --mode must be 'uprops', got '$MODE'"; exit 1; }
# Or check in a wrapper script
validate_mode() {
    case "$1" in
        uprops) return 0 ;;
        *) echo "Invalid mode: '$1'. Only 'uprops' is supported."; return 1 ;;
    esac
}

When it happens

Trigger: Passing --mode with any value other than 'uprops' (e.g. --mode uprops2, --mode coll, --mode break, or a typo). The option parser stores the value and this check rejects it. Unlike genrb errors that call exit(), this returns U_ILLEGAL_ARGUMENT_ERROR to the main function for normal process exit handling.

Common situations: Following outdated documentation or tutorials that reference modes no longer supported; typo in the mode value; copy-pasting a command from a script written for a different ICU version that had additional modes; habitually specifying --mode even though 'uprops' is the only option.

Related errors

• command already set when parsing -d
• command already set when parsing -t\n
• error in command line argument "%s"\n
• error in command line argument "%s"\n
• %s: error in command line argument "%s"\n

AI-assisted analysis of nodejs/node@1b2de5e052 (2026-08-13). Data as JSON: /api/errors/582dea9fcd476940. Report an issue: GitHub.