Relates to MC-124065

The bug

When spawn eggs set to spawn entities which aren't any of the standard set (available in the Creative inventory in 17w46a and prior, and with their own IDs in 17w47a onwards) are upgraded to a modern version such as 1.18.2, they are set to pig spawn eggs. The name of the pig spawn egg overwrites the name the spawn egg used in previous versions, making it impossible to tell what the egg spawns in-game without using it.

How to reproduce

1. Obtain a nonstandard spawn egg via one of the two commands below in a pre-1.13 version
2. Take note of the spawn egg's name
3. Upgrade the world with this spawn egg to the latest version
4. Take note of the spawn egg's name

Example commands

• 1.3.1 to 1.8.9 ender dragon spawn egg:

  /give @p spawn_egg 1 63

• 1.12.2 wither spawn egg:

  /give @s spawn_egg 1 0 {EntityTag:{id:"minecraft:wither"}}

Expected results

The spawn egg's name would be retained in some form as to make it clear what entity the item spawns.

Actual results

The item takes on the name of "Pig Spawn Egg", making it impossible to tell what it actually spawns.

How to fix

When upgrading spawn eggs, the game should check what entity ID is assigned to it. If it doesn't match one of the spawn eggs in 1.13+ with dedicated item IDs, then it should be given a custom name consisting of the entity's display name followed by " Spawn Egg".