Aliasing legacy JSON

When you port powers from another mod, or rename something, old data packs shouldn't break. Apoli's aliasing lets one registered type answer to several IDs, accept old field names and add defaults, all before your codec runs. Your codec stays clean, and the compatibility lives in the registration.

AliasingOptions

Pass an AliasingOptions as the third argument when registering:

PowerTypeRegistry.register(
    MyMod.id("attribute"),
    new AttributePower(),
    AliasingOptions.builder()
        .addTypeAlias(MyMod.id("conditioned_attribute"))
        .build()
);

Now both mymod:attribute and mymod:conditioned_attribute load through AttributePower.

The builder has these methods:

Method	Effect
`addTypeAlias(id)`	The type also answers to this old ID.
`addTypeAlias(id, defaults)`	The same, and adds these field defaults for that alias only.
`renameField(old, new)`	Rewrites an old field name to its current name before parsing.
`build()`	Produces the options.

The same builder works for actions and conditions:

ActionTypes.ENTITY.register(
    MyMod.id("modify_resource"),
    new ModifyResourceAction(),
    AliasingOptions.builder().addTypeAlias(MyMod.id("change_resource")).build()
);

Field renames

If a field was called entity_action and is now self_action, rename it for the alias so the old JSON still parses. registerAliasFieldRenames maps the legacy field name for that one alias:

PowerTypeRegistry.register(
    MyMod.id("action_on_hit"),
    new ActionOnHitPower(),
    AliasingOptions.builder()
        .addTypeAlias(MyMod.id("self_action_on_hit"))
        .build()
);
PowerTypeRegistry.registerAliasFieldRenames(
    MyMod.id("self_action_on_hit"), Map.of("entity_action", "self_action"));

Injected defaults

registerAliasDefaults, and the two-argument addTypeAlias, fill in fields that the alias should imply. That is how apoli:modify_damage_dealt and apoli:modify_damage_taken are the same type with a different default for which side is affected:

PowerTypeRegistry.registerAliasDefaults(MyMod.id("modify_damage_taken"), Map.of("target_used", "true"));

Why do it this way

Your configCodec() only ever sees current IDs and field names, with no legacy branches.
All the compatibility is declared in one place, next to the registration.
Removing an alias later is a one-line change.

This is the pattern behind the many aliases across the data pack docs, such as change_resource, set_size and disguise_as_player.