Not really a bug, more of an oversight (apologies if this isn't the place to report this): pigs don't spawn as their "warm" variant in the desert, they spawn with the normal "temperate" skin instead, which does actually happen since they do spawn naturally in villages.
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Comments 5
Relates to MC-279235
The changelog's biome list is for naturally spawning ones, but a biome being listed for warm does not mean it spawns in that biome. Adding deserts to the warm pig's biome tag will not make warm pigs spawn naturally there, it would just change spawn egg/command ones. Saying the tag is missing a biome (and as such resulting pig being wrong) is not saying it should spawn there. Thus the changelog does not contradict the report.
See also MC-279235, which got triaged by Mojang.
Like MC-279235, I suggest generalizing this report (and make it the same as MC-279235, but for the warm biome tag).
The tag currently contains badlands, bamboo_jungle, eroded_badlands, jungle, savanna, savanna_plateau, sparse_jungle, windswept_savanna, and wooded_badlands, meaning the following warm biomes are missing: deep_lukewarm_ocean, desert, lukewarm_ocean, mangrove_swamp (per frog variant), warm_ocean, and, maybe (seems logical to me, but may be debatable), lush_caves.
Additionally, there's the nether biomes crimson_forest, basalt_deltas, nether_wastes, soul_sand_valley, and warped_forest, which may need to be added just to make warm variants spawn when using spawn eggs in the nether.
I don't know if I am being dumb, but isn't this working as intended or am I interpretating this bug wrong?