Anuken/Mindustry · error · IllegalArgumentException

: not found

Error message

${type.getSimpleName()}: not found: '${name}'

What it means

field(Class, name) reads a static field by reflection via type.getField(name).get(null). If the field is absent or resolves to null, it throws IllegalArgumentException with the class and field name. Note: because the catch(Exception) wraps NoSuchFieldException too, the message ('not found') can be emitted either by the explicit null check or by the wrapped reflection exception.

Solutions

  1. Verify the field name is a public static member of the target class.
  2. Correct typos against the class's source.
  3. Ensure the field is non-null at parse time.

Example fix

// before
field(Items.class, "coper")
// after
field(Items.class, "copper")
Defensive patterns

Strategy: try-catch

Validate before calling

// Check the static field exists and is non-null before reading.
try {
    java.lang.reflect.Field f = type.getField(name);
    if(f.get(null) == null) throw new IllegalStateException(type.getSimpleName() + "." + name + " is null");
} catch(NoSuchFieldException e){
    throw new IllegalStateException(type.getSimpleName() + " has no field '" + name + "'");
}

Type guard

boolean hasStaticField(Class<?> type, String name){
    try { return type.getField(name).get(null) != null; }
    catch(Exception e){ return false; }
}

Try / catch

try { Object v = field(MyClass.class, "NAME"); }
catch(RuntimeException e){ /* field() wraps NoSuchFieldException; log and degrade */ Log.err(e); }

Prevention

When it happens

Trigger: A JSON reference names a static field that does not exist on the target class (e.g. an item/block/color constant), or exists but holds null.

Common situations: Referencing a color constant, item, or block by a name that isn't a public static field on the resolved class; typo; using a field from the wrong class.

Related errors

AI-assisted analysis of Anuken/Mindustry@f695ad7e60 (2026-08-14). Data as JSON: /api/errors/dc5f434eca7fb7ef. Report an issue: GitHub.

Appendix: source

Thrown at core/src/mindustry/mod/ContentParser.java:1231

            throw new RuntimeException(e);
        }
    }

    Prov<UnitController> resolveController(String type){
        //this is used as a captured value to avoid parsing it multiple times
        var controller = supply(resolve(type, FlyingAI.class));
        return controller::get;
    }

    Object field(Class<?> type, JsonValue value){
        return field(type, value.asString());
    }

    /** Gets a field from a static class by name, throwing a descriptive exception if not found. */
    private Object field(Class<?> type, String name){
        try{
            Object b = type.getField(name).get(null);
            if(b == null) throw new IllegalArgumentException(type.getSimpleName() + ": not found: '" + name + "'");
            return b;
        }catch(Exception e){
            throw new RuntimeException(e);
        }
    }
    Object fieldOpt(Class<?> type, JsonValue value){
        try{
            return type.getField(value.asString()).get(null);
        }catch(Exception e){
            return null;
        }
    }

    void checkNullFields(Object object){
        if(object == null || object instanceof Number || object instanceof String || toBeParsed.contains(object) || object.getClass().getName().startsWith("arc.")) return;

        parser.getFields(object.getClass()).values().toSeq().each(field -> {
            try{

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