Any way to re-position the cursor _after_ expansion?

[bew]

For Lua I'm making a simple r snippet for return, but I want the following behavior:

Add a space after return only if needed, but always leave the cursor after the space.

So that expanding with (| is the cursor):

r|foo

Would insert return (with space) and end up with return |foo
And:

r| foo

Would insert return (no space, but move cursor to the right) and end up with return |foo

I tried to use inject the termcodes for moving the cursor but that doesn't work / inserts garbage:

s({trig = "r", desc = "return ..."}, {
  ls.function_node(function()
    local line = vim.api.nvim_get_current_line()
    local col = vim.fn.col(".")
    local char = line:sub(col, col)
    if char == " " then
      local move_right = vim.api.nvim_replace_termcodes("<C-g>U<Right>", true, false, true)
      return "return" .. move_right
    else
      return "return "
    end
  end)
})

And I couldn't find a post_expand callback 🤔

[L3MON4D3]

Oh, I think I have a nice way of achieving this: instead of moving the cursor after expansion, include any whitespace behind the cursor in the trigger!
While this is not possible with the trigger using the "plain" trigEngine, you can use resolveExpandParams to manipulate the region that is treated as the trigger (ie. deleted before expansion).

Moving the cursor reliably is more complicated I think, luasnip has a kind of queue for all movement-commands and I'd have to expose some way to enqueue into it (and add a callback that is invoked at the right time :D)

[bew]

Awesome, I managed to get the behavior I wanted with (using my dsl for snip def):

-- NOTE: Adds the space after `return` only if needed,
--   but _always_ leave the cursor after the space.
snip(
  "r",
  {
    desc = "return ...",
    -- Tweak what will be removed exactly before snip expansion
    -- It is used to remove extra spaces and always leave cursor after space after expansion.
    --
    -- SEE: https://github.com/L3MON4D3/LuaSnip/discussions/1271
    -- REF: https://github.com/L3MON4D3/LuaSnip/blob/33b06d72d220aa56/lua/luasnip/extras/postfix.lua#L13
    resolveExpandParams = function(_snip, line_to_cursor, matched, _captures)
      local pos0
      do
        local c = vim.api.nvim_win_get_cursor(0)
        pos0 = { row = c[1] - 1, col = c[2] }
      end
      local line = vim.api.nvim_get_current_line()
      local line_after_cursor = line:sub(vim.fn.col".")
      local extra_spaces = line_after_cursor:match"^%s+" or ""
      return {
        clear_region = {
          from = {pos0.row, pos0.col - #matched}, -- before snip match
          to = {pos0.row, pos0.col + #extra_spaces}, -- after spaces
        }
      }
    end,
  },
  {
    t"return "
  }
)

Will def' play with this and refactor it for use in more snippets ❤️
Love the flexibility of the plugin ✨✨