HMCL-dev/HMCL · error · IllegalArgumentException

Empty old version number

Error message

Empty old version number

What it means

GameVersionNumber.Old.parse throws IllegalArgumentException with the message 'Empty old version number' when asked to parse a legacy (pre-classic/alpha/beta) version identifier that is an empty string. The parser requires at least a type prefix character plus a digit, so empty input is rejected explicitly before the switch.

Solutions

1. Validate the version string is non-empty before calling the parser and substitute a sensible default (e.g. skip comparison or use Release.ZERO)
2. Fix the source data so the version id is populated
3. Wrap parsing in try-catch for IllegalArgumentException and treat empty as unknown version

Example fix

// before
GameVersionNumber v = GameVersionNumber.asGameVersion(config.version);
// after
if (config.version == null || config.version.isEmpty()) {
    return; // or use a default version
}
GameVersionNumber v = GameVersionNumber.asGameVersion(config.version);

static boolean isValidOldVersion(String v) {
    return v != null && !v.isEmpty();
}

try {
    GameVersionNumber v = GameVersionNumber.asGameVersion(raw);
} catch (IllegalArgumentException e) {
    log.warn("Invalid version '{}': {}", raw, e.getMessage());
}

When it happens

Trigger: Passing "" to GameVersionNumber parsing (e.g. via GameVersionNumber.asGameVersion or comparison helpers) when the version string came from an empty version field in a version.json, a missing manifest entry, or an unfilled config value.

Common situations: Custom version JSON with an empty id; profile/config data missing a version field; upstream version lists containing blank entries.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• {value}
• ${value}
• Malformed modpack configuration:
• name existing
• Texture url is empty

AI-assisted analysis of HMCL-dev/HMCL@24702dc5a0 (2026-09-10). Data as JSON: /api/errors/b4248cbffcd2e735. Report an issue: GitHub.

Appendix: source

Thrown at HMCLCore/src/main/java/org/jackhuang/hmcl/util/versioning/GameVersionNumber.java:234

        if (gameVersion instanceof LegacySnapshot snapshot) {
            String[] defaultVersions = Versions.DEFAULT_GAME_VERSIONS;
            for (int i = defaultVersions.length - 1; i >= 0; i--) {
                Release gaRelease = (Release) asGameVersion(defaultVersions[i]);

                if (gaRelease.compareToSnapshot(snapshot) > 0) {
                    return gaRelease;
                }
            }
        }

        return null;
    }

    public static final class Old extends GameVersionNumber {
        static Old parse(String value) {
            if (value.isEmpty())
                throw new IllegalArgumentException("Empty old version number");

            Type type;
            int prefixLength = 1;
            switch (value.charAt(0)) {
                case 'r':
                    if (!value.startsWith("rd-")) {
                        throw new IllegalArgumentException(value);
                    }

                    type = Type.PRE_CLASSIC;
                    prefixLength = "rd-".length();
                    break;
                case 'i':
                    if (value.startsWith("inf-")) {
                        type = Type.INFDEV;
                        prefixLength = "inf-".length();
                    } else if (value.startsWith("in-")) {
                        type = Type.INDEV;

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