Bug with looting and shulker.

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Confirmed on 18w22c. I even checked the JSON file of the shulker loot table in the vanilla data pack:

{
  "pools": [
    {
      "conditions": [
        {
          "condition": "random_chance_with_looting",
          "chance": 0.5,
          "looting_multiplier": 0.0625
        }
      ],
      "rolls": 1,
      "entries": [
        {
          "type": "item",
          "name": "minecraft:shulker_shell"
        }
      ]
    }
  ]
}

Checked a zombie JSON file, it looks like the shulker will always drop 1 shulker shell.

[...]
"type": "item",
"name": "minecraft:rotten_flesh",
"weight": 1,
"functions": [{
            "function": "set_count",
            "count": {
                   "min": 0,
                   "max": 2
                   }
            },
            {
            [here]
            "function": "looting_enchant",
                       "count": {
                              "min": 0,
                              "max": 1
                        }
            [here]
            }
[...]

High level enchantments are not supported (MC-10755). Also, this looks intended anyway.

With simple looting lvl3 not supports too.

I found more than 200+ bugs in Minecraft, I can tell it in all instructions.