mini.pairs: auto-insert semicolons?

[mrjones2014]

I'd like to auto-insert semicolons in Nix code, e.g. when the code is like

{
  some_thing = 
}

when I type a { at the end of the line, I'd like it to expand to the following, where | is my cursor position.

{
  some_thing = { | };
}

I tried this in a ftplugin for Nix, but this puts my cursor between the } and the ; instead of between {}:

local mp = require('mini.pairs')

mp.map_buf(0, 'i', '{', { action = 'open', pair = '{};', register = { cr = false } })
mp.map_buf(0, 'i', '}', { action = 'close', pair = '{};', register = { cr = false } })

If possible, I'd also like to not insert the semicolon if the {} is inside a list type, like

{
  things = [
    # since this is inside square brackets, don't add the ;
    { }
  ];
}

[echasnovski]

I am afraid, this is not possible with 'mini.pairs':

• Both "open" and "close" parts of a pair are expected to be a single character. More than that is not supported. So no "};" as "close" part is supported.
• Condition on whether a pair should be included can be made only on two character neighborhood. So no conditions like "it is inside a list type" are supported.