Anuken/Mindustry · error · IllegalArgumentException

Attribute definitions must be objects, e.g. {heat: 10}

Error message

Attribute definitions must be objects, e.g. {heat: 10}

What it means

Thrown by the Attributes parser in ContentParser when the JSON value for an Attributes-typed field is not a JSON object. Attributes is a name->float map (e.g. {heat: 10}), so strings, numbers, or arrays are invalid.

Source

Thrown at core/src/mindustry/mod/ContentParser.java:96

            }
            Class<? extends Effect> bc = resolve(data.getString("type", ""), ParticleEffect.class);
            data.remove("type");
            Effect result = make(bc);
            readFields(result, data);
            return result;
        });
        put(Sortf.class, (type, data) -> field(UnitSorts.class, data));
        put(Interp.class, (type, data) -> field(Interp.class, data));
        put(Blending.class, (type, data) -> field(Blending.class, data));
        put(CacheLayer.class, (type, data) -> field(CacheLayer.class, data));
        put(Attribute.class, (type, data) -> {
            String attr = data.asString();
            if(Attribute.exists(attr)) return Attribute.get(attr);
            return Attribute.add(attr);
        });
        put(Attributes.class, (type, data) -> {
            if(!data.isObject()){
                throw new IllegalArgumentException("Attribute definitions must be objects, e.g. {heat: 10}");
            }
            Attributes attr = new Attributes();
            for(var child : data){
                Attribute value = Attribute.exists(child.name) ? Attribute.get(child.name) : Attribute.add(child.name);
                attr.set(value, child.asFloat());
            }
            return attr;
        });
        put(BuildVisibility.class, (type, data) -> field(BuildVisibility.class, data));
        put(Schematic.class, (type, data) -> {
            Object result = fieldOpt(Loadouts.class, data);
            if(result != null){
                return result;
            }else{
                String str = data.asString();
                if(str.startsWith(Vars.schematicBaseStart)){
                    return Schematics.readBase64(str);
                }else{

View on GitHub (pinned to f695ad7e60)

Solutions

1. Rewrite the value as a JSON object mapping attribute names to floats.
2. Verify each attribute name either exists or will be auto-added via Attribute.add.
3. Distinguish Attributes (the map) from a single Attribute reference (which accepts a string).

Example fix

// before
"attributes": "heat"
// after
"attributes": { "heat": 10 }

// Guard: Attributes must be a JSON object (map of name->float).
boolean validAttributes(JsonValue v) {
    return v.isObject();
}

When it happens

Trigger: A mod JSON block sets an `attributes` field (or any Attributes-typed field) to a non-object value such as "heat", 10, or [1,2].

Common situations: Mod authors copy the wrong example, pass a single attribute name string instead of a map, or confuse Attributes with a single Attribute.

Related errors

• Unknown status effect: '
• Unknown unit command name:
• Unit commands must be strings.
• Unknown unit stance name:
• Unit stances must be strings.

AI-assisted analysis of Anuken/Mindustry@f695ad7e60 (2026-08-14). Data as JSON: /api/errors/920caedefe8cd663. Report an issue: GitHub.