Anuken/Mindustry · error · IllegalArgumentException

name is null

Error message

name is null

What it means

Thrown by the GenRegion constructor when name is null. GenRegion extends AtlasRegion and stores the name to identify a sprite region in the packing pipeline; a null name is treated as a programmer error, not user input, so it fails fast with IllegalArgumentException. This guard runs only inside the build-time ImagePacker tool, never in shipped game code.

Source

Thrown at tools/src/mindustry/tools/ImagePacker.java:293

        replace(((GenRegion)region).name, image);
    }

    static void err(String message, Object... args){
        throw new IllegalArgumentException(Strings.format(message, args));
    }

    static void validate(TextureRegion region){
        if(((GenRegion)region).invalid){
            ImagePacker.err("Region does not exist: @", ((GenRegion)region).name);
        }
    }

    static class GenRegion extends AtlasRegion{
        boolean invalid;
        Fi path;

        GenRegion(String name, Fi path){
            if(name == null) throw new IllegalArgumentException("name is null");
            this.name = name;
            this.path = path;
        }

        @Override
        public boolean found(){
            return !invalid;
        }
    }

    static class PackIndex{
        @Nullable AtlasRegion region;
        @Nullable Pixmap pixmap;
        Fi file;

        public PackIndex(Fi file){
            this.file = file;
        }

View on GitHub (pinned to f695ad7e60)

Solutions

1. Trace the caller of 'new GenRegion(...)' and ensure the name argument is always a non-null, non-empty string.
2. If the name is derived from a file path, fall back to path.nameWithoutExtension() instead of passing null.
3. Add a unit test that constructs every region declared in pack.json and asserts a non-null name.
4. Fail earlier in the pipeline with a descriptive message naming the offending asset.

Example fix

// before
gen = new GenRegion(name, file);  // name may be null

// after
String regionName = name != null ? name : file.nameWithoutExtension();
if(regionName == null || regionName.isEmpty()) throw new IllegalStateException("Region has no name: " + file);
gen = new GenRegion(regionName, file);

// Before constructing a GenRegion
String regionName = name != null ? name : (path != null ? path.nameWithoutExtension() : null);
if(regionName == null || regionName.isEmpty()){
    throw new IllegalStateException("Cannot create region with null name for path: " + path);
}
new GenRegion(regionName, path);

static boolean hasValidRegionName(String name, Fi path){
    return name != null && !name.isEmpty() || (path != null && path.nameWithoutExtension() != null);
}

When it happens

Trigger: Invoking new GenRegion(null, path), or calling code that derives the name from a file path whose name resolved to null (e.g. a sprite entry with no filename, or a region generator that returns null on a missing mapping).

Common situations: Adding a new sprite whose pack.json entry has no name; refactoring region generation so the name argument is dropped; a malformed/empty filename in the assets list feeding a null name; an upstream change to Fi naming returning null on an unusual path.

Related errors

• Image dimensions are not divisible by 4: {width}x{height}
• Data must be exactly 32 bytes (length: ${data.length})
• Max image size exceeded
• Cache file for asset {path} not found!
• Map has no cores!

AI-assisted analysis of Anuken/Mindustry@f695ad7e60 (2026-08-14). Data as JSON: /api/errors/536f9fc1912449e4. Report an issue: GitHub.