Update Leash Syntax To Entity

[tibisabau]

Problem

Leash-related syntax (leash holder expression, leash/unleash effects, and is leashed condition) only accepted LivingEntity types, preventing users from leashing boats and other non-living leashable entities. Users had to resort to reflection workarounds to leash boats.

Solution

Updated all three leash-related syntax files to accept any Entity type and utilize Paper's Leashable interface (available in Paper 1.21+) with runtime version checking via Skript.classExists(). The implementation falls back to the legacy LivingEntity.getLeashHolder() approach for older server versions, maintaining full backward compatibility.

Modified Files:

• ExprLeashHolder.java - Changed from SimplePropertyExpression<LivingEntity, Entity> to SimplePropertyExpression<Entity, Entity>
• EffLeash.java - Updated to accept Expression<Entity> instead of Expression<LivingEntity> for both leash and unleash operations
• CondLeashed.java - Changed from PropertyCondition<LivingEntity> to PropertyCondition<Entity>

Testing Completed

• Created comprehensive test files:
  • ExprLeashHolder.sk - Tests leash holder expression with wolves and non-leashable entities (snowballs)
  • EffLeash.sk - Tests leash/unleash effects with living entities, non-living entities, and multiple entities
  • CondLeashed.sk - Tests is leashed condition with various entity types
• ./gradlew clean build - SUCCESS (0 errors)
• ./gradlew clean quickTest - SUCCESS (all tests passed including "leash effect", "leash holder expression", and "is leashed condition")

Supporting Information

The implementation uses Paper's io.papermc.paper.entity.Leashable interface which provides consistent leashing behavior across all entity types. Non-leashable entities return null/false without throwing exceptions, ensuring graceful handling of edge cases.

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Completes: #8239
Related: none
AI assistance: GitHub Copilot with Claude Sonnet 4.5 model

The code in this pull request was generated by GitHub Copilot with the Claude Sonnet 4.5 model.

[TheMug06]

Duplicate of #8241

[TheMug06]

Tests contain lines attempting to leash entities to blocks, while the syntax does not offer support for this. Also never checks whether syntax even succeeded See sovde's comments

Instanceof checks do not need to have the entire path of the class, can just check for Leashable instead of io.papermc.paper.entity.Leashable.

Perhaps add a new version to @Since to indicate changes to what entities can be leashed.

The rest looks good to me!

[Absolutionism]

Since this is a feature PR, it will be added in Skript 2.15, which the minimum MC version will be 1.21.1 (only a singular bump in the minor version). 1.21.1 contains Leashable, so there is no need for the SUPPORTS_LEASHABLE

[TheMug06]

Description of EffLeash is not accurate, as Ender Dragon, Wither, and Bat are all subinterfaces of Leashable, thus should be leashable (?)

New version in @Since should be INSERT VERSION, not 2.10, which has been out for a long time. (AI does not know this.) Its description (currently entities) could also be slightly more descriptive, as it doesn't really say anything about what changed after the new version.

[TheMug06]

I still don't really love the since, the differences between LivingEntity and Leashable are not just non-living entities.

[TheMug06]

For Since, any entity type is not accurate either, as not every entity type is Leashable (Think Player, Armor Stand).

Additionally, asserting whether a zombie is not leashed with "... non-leashable entity ..." makes no sense, as zombies are leashable.

[sovdeeth]

@tibisabau have you played Minecraft before? It seems like a lot of these changes are just blind guesses in the dark. I suggest you reference Paper's javadocs for Leashable or at least the minecraft wiki.

Tests failing due to leashing entity to self working in 1.21.3/1.21.1.

[TheMug06]

Skript users probably will not know what entities implementing Leashable means... Perhaps think of something that,

1. Makes sense in the context of the change
2. Will make sense to Skript users

[sovdeeth]

this is a bit iffy, we should really be checking exact versions it should work on.
But whatever, it's probably ok.