Mobs can spawn from spawners even if gamerule doMobSpawning is set to false

Is this still an issue in 1.15.2?

yes I believe this is still a issue. I have been trying for over 2 weeks to get Villagers to respawn more villagers and turtles to do the same thing but it does not. I get the hearts but that is all.

... that's completely irrelevant to this ticket though?

Although this still occurs in 1.15.2, I think there are valid reasons to leave it as-is. In my mind the phrase doMobSpawning conveys whether or not the mob spawning algorithm should be run, which spawners are separate from. I personally use this behavior in test worlds to design and test mob spawners. Players who don't want any mobs at all, including from mob spawners can set the difficulty to peaceful.

I tested this on 1.14 and mobs will spawn from spawners even with doMobSpawning set to false.

This is an intended feature. The doMobspawning gamerule controls when the game tries to run the mob spawning algorithm and attempts spawn a mob, and setting the gamemode to false prevents the mob spawning algorithm. Spawners have nothing to do with the algorithm.

Can confirm in 20w51a.

I feel like there SHOULD be some way to disable Mob Spawners without going through and literally removing them all from the map until the final build (where I am certain I will have forgotten to place many) without having entities cram to the chunk limit when working on maps. I feel like this gamerule SHOULD apply here.

Can confirm in 1.17.

Can confirm in 1.17.1.