Anuken/Mindustry · error · IllegalArgumentException

You are missing a "${key}". It must be added before the file

Error message

You are missing a "${key}". It must be added before the file can be parsed.

What it means

getString(value, key) throws when value.has(key) is false. It is a helper used to read mandatory string fields (e.g. getType() requires "type"). The message names the exact missing key so the author knows what to add.

Source

Thrown at core/src/mindustry/mod/ContentParser.java:907

            case "flying" -> UnitEntity::create;
            case "mech" -> MechUnit::create;
            case "legs" -> LegsUnit::create;
            case "naval" -> UnitWaterMove::create;
            case "payload" -> PayloadUnit::create;
            case "missile" -> TimedKillUnit::create;
            case "tank" -> TankUnit::create;
            case "hover" -> ElevationMoveUnit::create;
            case "tether" -> BuildingTetherPayloadUnit::create;
            case "crawl" -> CrawlUnit::create;
            default -> throw new IllegalArgumentException("Invalid unit type: '" + value.asString() + "'. Must be 'flying/mech/legs/naval/payload/missile/tether/crawl'.");
        };
    }

    private String getString(JsonValue value, String key){
        if(value.has(key)){
            return value.getString(key);
        }else{
            throw new IllegalArgumentException("You are missing a \"" + key + "\". It must be added before the file can be parsed.");
        }
    }

    private String getType(JsonValue value){
        return getString(value, "type");
    }

    private <T extends Content> T find(ContentType type, String name){
        Content c = Vars.content.getByName(type, name);
        if(c == null && currentMod != null) c = Vars.content.getByName(type, currentMod.name + "-" + name);
        if(c == null) throw new IllegalArgumentException("No " + type + " found with name '" + name + "'");
        return (T)c;
    }

    private <T extends Content> TypeParser<T> parser(ContentType type, Func<String, T> constructor){
        return (mod, name, value) -> {
            T item;
            if(allowPatching && locate(type, name) != null){

View on GitHub (pinned to f695ad7e60)

Solutions

1. Add the named key with a valid string value to the JSON.
2. Confirm the field name spelling matches the message exactly.

Example fix

// before
{ "name": "my-thing" }  // type missing
// after
{ "name": "my-thing", "type": "flying" }

if(!value.has(key)){
    throw new IllegalStateException("Missing required field '" + key + "' in " + value.toString());
}

When it happens

Trigger: A content JSON omits a field that getString was asked to read (currently "type" via getType()). Any caller of getString passing a key the JSON lacks triggers it.

Common situations: A unit/block/etc. JSON missing the required "type" field; refactoring that introduces a new required field.

Related errors

• Team field missing.
• ${type.getSimpleName()}: not found: '${name}'
• Unknown consumption type: '${child.name}' for block '${block
• Blocks cannot be larger than ${maxBlockSize}
• Unit '${name}' has an incorrect type. Types must be strings.

AI-assisted analysis of Anuken/Mindustry@f695ad7e60 (2026-08-14). Data as JSON: /api/errors/de0927def77243f8. Report an issue: GitHub.