The answer object returns an empty array for tags

Question

Since version 2.1, the answer object has a field called tags. However, sometimes, an empty array or even nothing is returned in this field:

Example with the filter !-*f(6t0Vk01e.

Am I doing something wrong or is this a bug?

Answer 1

This is a bug and seems (based on a series of A/B tests) to be linked with the body_markdown property.

That is, if your filter returns the tags array, it works:

"items": [ {
    "tags": [ "batch-file", "cmd" ],
    "answer_id": 42292030
  }, {
    "tags": [ "ios", "arrays", "swift" ],
    "answer_id": 42295110
  },
  etc...

, unless body_markdown is also selected:

"items": [ {
    "tags": [],
    "answer_id": 42295122,
    "body_markdown": "`ExecuteScalar` fetches the first column value of the first row. So, it won't make..."
  }, {
    "tags": [],
    "answer_id": 42294953,
    "body_markdown": "The git revert documentation provides the syntax like\r\n\r\n    git revert [--[no-]..."
  },
  etc.