The bug
Water and lava buckets can no longer be emptied by looking at a water or lava source block. However, when trying to do that, a sound still plays.
To reproduce
Get a water bucket
Switch into Survival mode
Look at a water source block
Use the bucket
→ ❌ The bucket doesn't get emptied, but a sound gets played
Videos
Holding down right click:
Water:
Lava:
Linked issues
is duplicated by
Attachments
Comments

Is that a feature? Seems like a downgrade. It is annoying to not be able to empty a bucket into a source block, and rather place the water from the bucket outside and place a block to get rid of it. Fairly frustrating.

I see where you’re coming from, but I suppose this feature makes sense.
Maybe a suggested fix is to make you able to place the water on top of the source block

There's no way this is a feature. It was not listed in the changelog and it only makes building with water even more annoying. Nothing changed specifically for buckets or their interactions with liquids in this snapshot.

As far as I can tell, there was nothing in the changelog about this, but source analysis shows there were some minor changes to the bucket fluid placing behavior. A likely culprit is that placing the fluid now returns the result of attempting to set the block state, where before it did not.
Since the block state doesn't actually change, the fluid placement now fails.

I agree this is annoying, I believe this feature was originally added as a way to easily empty water buckets. It doesn't make sense when you're emptying a bucket into a single source block sure, but when you think of it as emptying it into an ocean it makes more sense. Either way I believe this is a bug not a feature, since it has been in the game for so long and because it is much more convenient to empty a water bucket into other water instead of placing water on the ground and replacing it with a block.

Yes, this does not make sense as a "feature" – in particular, the old behavior let an infinite water source serve also as a sink to empty buckets into. This change would mess up generations of base designs assuming the old behavior! Not to mention there's no replacement behavior – with this bug the only way to get rid of a water block is to place a solid block over it.

20w19a

Not sure if this was true previously, but as of 20w19a, I am able to empty a bucket into a bubble column, but still not normal water source blocks.

also cant empty water bucket on redstone ore unless your shifting so its probably a bug with the water bucket
@unknown, that's a separate bug, MC-165510.

This issue is also with buckets containing fish (Tropical, Cod, Salmon). The same issue persists and the bucket does not empty nor does the fish get released.
Can confirm. This happens because you can no longer empty buckets by looking at a source block of that block.