Apply i-textobject even if cursor is only covered by o-textobject

[embie27]

Contributing guidelines

• I have read CODE_OF_CONDUCT.md

Module(s)

mini.ai

Question

I have implemented a textobject mfor LaTeX-math using treesitter. The current behaviour using the cover-search method is the following. Assume that I am in the following situation, where |is the cursor:

\( | \pi \)

Then hitting vim, does not find a textobject because the cursor is not covered by the inner part (whitespaces are not counted as inner by my treesitter query). The behaior that I would like to achieve is that in this case \piis selected because the outer textobject covers the cursor.

I could not find a way to achieve this by simply changing options of mini.ai. Hence, I assume that I would need to implement a custom search method to achieve the desired behavior. Is this assumption correct? If so, could you point me to a good starting place to implement this search method?

[echasnovski]

This is indeed correct for custom textobjects with specification generated from gen_spec.treesitter() and more generally for callable specification which returns single or multiple regions. Searching for the "best" region is then done internally by 'mini.ai' based on the current reference region, search method, etc. As gen_spec.treesitter() returns an array of regions for i textobject and doesn't account for a during querying for them, the behavior you describe is indeed expected.

In theory, it is possible to update gen_spec.treesitter() querying logic to something like "search regions for both a and i textobjects, find the best (the smallest width) covering region for a, and then find the appropriate region (probably the largest width) for i that is inside a region". But I don't think this behavior is universally expected enough to be implemented in gen_spec.treesitter().

My suggestions would be the following (from most to least advisable in my opinion):

• Use explicit in and il to select these inner parts when outside of them. It usually quite soon becomes pretty natural to treat being in the whitespace padding of brackets as being "outside" of the inner part.

• Try to use nested patterns specification instead of tree-sitter. It might not be 100% robust solution, but it will behave the way you describe: it finds matches based on the last nested pattern (which usually covers whole a) and then extracts either a or i part. This is possible because there is a one-to-one relation here between a and i parts, which is generally speaking not present in tree-sitter case.

• Implement own specification based on the output of gen_spec.treesitter(). So it might be something like:

  local ai = require('mini.ai')
  local ref_ts_spec = ai.gen_spec.treesitter({ a = '@function.outer', i = '@function.inner' })
  -- See `:h MiniAi.find_textobject()` for arguments descriptions
  local my_ts_spec = function(ai_type, id, opts)
    local a_regions = ref_ts_spec(ai_type)
    if ai_type == 'a' then return a_regions end
    local i_regions = ref_ts_spec('i')
    -- Do the matching. Might be non-trivial.
  end
  ai.setup({ custom_textobjects = { m = my_ts_spec } })

Hope this helps.