The bug
It is no longer possible use items while looking at an entity.
This is caused by MC-127094 being fixed.
To reproduce
Look at an entity
Get some food
Make sure you're hungry
Try to eat
→ ❌ That doesn't work
Affected Items
(List may be incomplete)
Shields
Splash potions
Milk buckets
Honey bottles
Buckets (In Creative; milking cows/mooshrooms)
Bowls (In Creative; milking red/brown mooshrooms)
Bows
Crossbows (Loaded/Unloaded)
Tridents
Empty maps
Snowballs
Eggs
Food
Potions
Lingering potions (Same as splash potions)
Bottle o' Enchanting
Armor (Prevents players from equipping)
Fishing rods
Linked issues
is duplicated by
Comments

Confirmed in 19w38a and 19w38b.
This issue appears to be from the "startUseItem" (using 19w39a obfuscation map names for research) method in Minecraft class.
Snippet:
switch (this.hitResult.getType()) {
case ENTITY: {
EntityHitResult entityHitResult_1 = (EntityHitResult)this.hitResult;
Entity entity_1 = entityHitResult_1.getEntity();
if (this.gameMode.interactAt(this.player, entity_1, entityHitResult_1, interactionHand_1) == InteractionResult.SUCCESS || this.gameMode.interact(this.player, entity_1, interactionHand_1) == InteractionResult.SUCCESS) {
this.player.swing(interactionHand_1);
}
return; // This forces to skip item use logic; compare to block one below
}
case BLOCK: {
BlockHitResult blockHitResult_1 = (BlockHitResult)this.hitResult;
int int_1 = itemStack_1.getCount();
InteractionResult interactionResult_1 = this.gameMode.useItemOn(this.player, this.level, interactionHand_1, blockHitResult_1);
if (interactionResult_1 == InteractionResult.SUCCESS) {
this.player.swing(interactionHand_1);
if (!itemStack_1.isEmpty() && (itemStack_1.getCount() != int_1 || this.gameMode.hasInfiniteItems())) {
this.gameRenderer.itemInHandRenderer.itemUsed(interactionHand_1);
}
return;
}
if (interactionResult_1 != InteractionResult.FAIL) break;
return;
}
}
As you can see, the entity block forces to skip the logic for item interaction even though two types of entity interactions may request to "PASS" instead of "FAIL".
Suggested:
case ENTITY: {
EntityHitResult entityHitResult_1 = (EntityHitResult)this.hitResult;
Entity entity_1 = entityHitResult_1.getEntity();
InteractionResult result1 = this.gameMode.interactAt(this.player, entity_1, entityHitResult_1, interactionHand_1);
InteractionResult result2;
if (result1 == InteractionResult.SUCCESS || (result2 = this.gameMode.interact(this.player, entity_1, interactionHand_1)) == InteractionResult.SUCCESS) {
this.player.swing(interactionHand_1);
}
if (result1 == InteractionResult.PASS && result2 == InteractionResult.PASS) {
break; // Continue to item use logic
}
return;
}
This also causes the Zombie Doctor advancement to be impossible
That I cannot confirm. You just cannot look directly at the zombie villager while curing it, but you can throw a potion of weakness at it through other means. Feeding it a golden apple works as well.

Affects bedrock edition
Please add some of these to the Affected Items:
Potions
Lingering potions (Same as splash potions)
Bottle o' Enchanting
Armor (Prevents players from equipping)
This issue may have "temporarily fixed" the issue MC-141494 as the items are no longer used. Though if this issue is fixed, the issue MC-141494 would return.