`Player#applyMending(amount)` does not apply mending to itemstacks whose material has no default `max_damage`

Expected behavior

Both paths repair the item.

Observed/Actual behavior

CraftPlayer#applyMending gates the repair on the item prototype instead of the stack:

// CraftPlayer.java
if (!itemstack.isEmpty() && itemstack.getItem().components().has(DataComponents.MAX_DAMAGE)) {

itemstack.getItem().components() is the default component map of the Item, not of the stack. A stack
that became damageable through its own max_damage/damage components, for example a player_head
used as custom equipment, fails this check and is never repaired.

The check is also redundant: the stack was just selected by
EnchantmentHelper.getRandomItemWith(REPAIR_WITH_XP, handle, ItemStack::isDamaged), and isDamaged()
already requires has(MAX_DAMAGE) on the stack.

ExperienceOrb#repairPlayerItems does not have this check, so the two paths disagree.

Steps/models to reproduce

/give @s player_head[max_damage=100,damage=50,enchantments={mending:1},equippable={slot:"head"},minecraft:max_stack_size=1]

Wear it, then:

• Walk into an experience orb (/summon minecraft:experience_orb ~ ~ ~ {Value:100}) → repaired.
• Have a plugin call player.giveExp(100, true) → not repaired, the full amount goes to the XP bar.

The same test with diamond_helmet[damage=50,enchantments={mending:1}] is repaired on both paths,
because minecraft:diamond_helmet carries max_damage in its prototype.

Plugin and Datapack List

None / just a test plugin

Paper version

This server is running Paper version 26.2-124-ver/26.2@22ca6c7 (2026-09-15T17:48:49Z) (Implementing API version 26.2.build.124-stable)
You are running the latest version
Previous version: 26.2-60-1cb58fb (MC: 26.2)

Other

No response

Start in CraftPlayer.java at the CraftPlayer#applyMending(amount) check that reads the item prototype, and compare it with ExperienceOrb#repairPlayerItems. Reproduce the difference using the player_head command and both experience paths. Done means a damaged stack with its own max_damage and damage components is repaired through player.giveExp(100, true) as well as by an experience orb.