[compressedgas]

Trailing in languages which support ending the last item with a comma as this follows the usage of the semicolon.

  [ 1, 
    2, 
  ]

Leading otherwise as no language I can remember supports a leading comma on the first item:

  [ 1 
  , 2 
  ]

The entire point of this is to avoid needing to edit the prior line when inserting items into an existing lexical list this makes the diffs just:

  +

instead of:

  - 
  +
  +

If you don't care about how your line diffs look, don't bother. Just auto-format your code instead.