Access wideners provide a way to loosen the access limits of classes, methods or fields. Access wideners are similar to the commonly known Access Transformers.

Access wideners should only be used where mixin does not currently provide a means to do so. There are currently only 2 cases where mixins are not sufficient:

• Needing to access a (package) private class, especially for the purpose of shadowing or accessing a field or method in a mixin.
• Being able to override final methods or subclass final classes.
  • Before you consider overriding final methods, try mixin injecting in final methods first!
  • If you want to subclass a class with only (package) private constructors, wideners are a good choice.

• Fabric-loader 0.8.0 or higher
• Loom 0.2.7 or higher

A specific file format is used to define the access changes included in your mod. To aid IDE's you should use the .accesswidener file extension.

The file must start with the following header, namespace should match the mappings namespace of your mod's source code, this is usually named. Loom will remap the access widener file for you into intermediary along with your mod. If you use a custom RemapJarTask, set remapAccessWidener property on it to true to ensure this happens.

accessWidener	v1	<namespace>

Access widener files can have blank lines and comments starting with #

# Comments like this are supported, as well as at the end of the line

Any whitespace can be used to separate in the access widener file, tab is recommended.

Class names are separated with a / and not .

For inner classes, you should use $ instead of /

Class access can be changed by specifying the access and the class name as named the mappings namespace defined in the header.

<access>   class   <className>

1. access can be accessible or extendable

Method access can be changed by specifying the access, class name, method name and method descriptor as named the mappings namespace defined in the header.

<access>   method   <className>   <methodName>   <methodDesc>

1. access can be accessible or extendable
2. classname is the owner class
3. methodName is the method name
4. methodDesc is the method descriptior

Field access can be changed by specifying the access, class name, field name and field descriptor as named the mappings namespace defined in the header.

<access>   field   <className>   <fieldName>   <fieldDesc>

1. access can be accessible or mutable
2. className is the owner class
3. fieldName is the field name
4. fieldDesc is the field descriptor

Extendable should be used where you want to extend a class or override a method.

• Classes are made public and final is removed
• Methods are made protected and final is removed

Making a method extendable also makes the class extendable.

Accessible should be used when you want to access a class, field or method from another class.

• Classes are made public
• Methods are made public and final if private
• Fields are made public

Making a method or field accessible also makes the class accessible.

Mutable should be used when you want to mutate a final field

• Fields have final removed

The access widener file location must be specified in your build.gradle and in your fabric.mod.json file. It should be stored in the resources as it needs to be included in the exported jar file.

minecraft {
	accessWidener "src/main/resources/modid.accesswidener"
}

...
 
"accessWidener" : "modid.accesswidener",
 
...