When crafting firework rockets and firework stars, if you have different sized stacks in the crafting window, shift+clicking to craft all of the item will craft multiple types of firework rockets or firework stars.
Examples:
Rockets:
2 gunpowder + 1 gunpowder + 2 paper
Mousing over the result says "Flight Duration: 2". Shift+click will craft 3 of those and also 3 with "Flight Duration: 1".Stars:
2 gunpowder + 2 cyan dye + 1 wither skeleton skull
Mousing over the result says "Creeper-shaped". Shift+click will craft 1 of those and also 1 with "Small Ball".
I noticed this result first in a multiplayer survival world at a crafting table. I then went into a creative single-player world and tested at a crafting table, changed to survival, and tested in the inventory. This happened each time I tested.
This issue is a duplicate of one I submitted last night: MC-185555. I am resubmitting, because that one was marked as resolved, as it looks similar to MC-17431, which has been fixed in the latest snapshot. However, the symptoms of this bug were not reported anywhere in MC-17431, as that bug involved an enchanting table taking away data tags, and this bug involves crafting creating multiple sets of data tags. Further, after seeing it was marked as a duplicate of a resolved bug, I tested in the latest snapshot. This bug (crafting) is still present, while the old bug (enchanting) has indeed been fixed.
My apologies, the parent ticket is MC-4309.