[mini.pairs] Better pairs

[drowning-cat]

Note

Only allow expanding pairs before %s, >, ), ], }, ,

local MiniPairs = require("mini.pairs")
MiniPairs.setup({
  mappings = {
    ["("] = { neigh_pattern = "[^\\][%s>)%]},]" },
    ["["] = { neigh_pattern = "[^\\][%s>)%]},]" },
    ["{"] = { neigh_pattern = "[^\\][%s>)%]},]" },
    ['"'] = { neigh_pattern = "[%s<(%[{][%s>)%]},]" },
    ["'"] = { neigh_pattern = "[%s<(%[{][%s>)%]},]" },
    ["`"] = { neigh_pattern = "[%s<(%[{][%s>)%]},]" },
  },
})

[loichyan]

I'm using an envoled version of LazyVim's pairing logic, adding the ability to handle unbalanced pairs (within the current line), triple quotes (code fences in Markdown, doc comments in Python, etc.), and string literals:

---Counts unbalanced open or close characters.
---@param line string
---@param op string # open character
---@param cl string # close character
---@return integer,integer # count of open and close characters
local count_unlanced = function(line, op, cl)
  local no, nc = 0, 0
  for i = 1, #line do
    local ch = line:sub(i, i)
    if ch == op then
      -- Found an unbalanced open character
      no = no + 1
    elseif ch ~= cl then
      -- Ignore non-pairing characters
    elseif no > 0 then
      -- Found a balanced pair
      no = no - 1
    else
      -- Found an unbalanced close character
      nc = nc + 1
    end
  end
  return no, nc
end

local smart_open = function(open, pair, neigh_pattern)
  if vim.fn.getcmdline() ~= "" then return open(pair, neigh_pattern) end

  local op, cl = pair:sub(1, 1), pair:sub(2, 2)
  local line, cur = vim.api.nvim_get_current_line(), vim.api.nvim_win_get_cursor(0)
  local row, col = cur[1], cur[2]

  -- Handle triple quotes
  if op == cl and line:sub(col - 1, col) == op:rep(2) then
    return op .. "\n" .. op:rep(3) .. vim.api.nvim_replace_termcodes("<Up>", true, true, true)
  end

  -- Disable pairing in string literals
  local ok, captures = pcall(vim.treesitter.get_captures_at_pos, 0, row - 1, math.max(col - 1, 0))
  if ok and #captures == 1 and captures[1].capture == "string" then return op end

  -- Emit only an opening if unbalanced
  if line:len() < 500 then
    if op ~= cl then -- pairs
      local left, right = line:sub(1, col), line:sub(col + 1)
      local no, _ = count_unlanced(left, op, cl)
      local _, nc = count_unlanced(right, op, cl)
      if no < nc then return op end
    else -- quotes
      local _, n = line:gsub("%" .. op, "")
      if n % 2 ~= 0 then return op end
    end
  end

  return open(pair, neigh_pattern)
end

local orig_open = MiniPairs.open
MiniPairs.open = function(...) return smart_open(orig_open, ...) end

[echasnovski]

Thanks for sharing!

Is it a common inconvenience to have autoopen in other cases? My approach is that it is less mentally taxing to adapt "if you want a single character, then press <C-v> first" in any situation rather than have it semi-automated while still maybe having these kind of situations.

[loichyan]

ohhh! I haven't learnt about CTRL-V in insert mode. This is indeed a nice solution, after all the "smartest" is ourself :D

[drowning-cat]

Note

It would be great to hear feedback from people using different languages.

I tried the reverse approach, restricting expansion where it shouldn’t happen, and quickly realized there are very few cases where I actually want quotes to expand. It’s also easy to understand: expansion only triggers in a few places, like before spaces and brackets.

• If I type a bracket/quote before a word, letter, digit, or punctuation (depending on the language), I usually want to wrap it.
• If I type a quote after a word, I want to close it.

YES	NO
(word	()word
(123	()123
name"	name""

Thanks for pointing out <C-v>. Now it’s clear why expansion is on by default.

[echasnovski]

It is mentioned in the help, reasonably early. Maybe it still needs to be more visible, though 🤔

[drowning-cat]

I guess it could be in the README.md, since people like me do not read the documentation thoroughly.
Something that gives a rough idea about the default pairing behavior.