How to insert text from lua function at cursor position (insert mode)

Question

I realize there is a similar question here but using vimscript. I have created a function that returns a uuid in lua. But I would like to assign this to a keymap and insert the text at the cursor position while in insert mode.

with the function below I can enter and return in the messages:

:print (require ("util.functions").uuid()) 

How can I get it in the buffer at the cursor position?

function M.uuid()
  math.randomseed(os.time())
  local random = math.random
  local template = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
  return string.gsub(template, "x", function()
    local v = random(0, 0xf)  -- v is a decimal number 0 to 15
    return string.format("%x", v) --formatted as a hex number
  end)
end

return M

Answer 1

Some stuff you might know already so don't mind those. Vim/neovim works with buffers in general so looking for buffers in the docs or in the :help will show a lot of stuff.

What you are looking for is nvim_buf_set_text to set the text into the buffer. This method takes starting row and column positions. This method is best suited for inserting text or delete/replace. See the linked doc for other suggestions.

What you want to do is place the uuid in the buffer but we also need the row and column position for nvim_buf_set_text for this we will use nvim_win_get_cursor

--[[ Your uuid function global and renamed for example --]]
function generate_uuid()
    math.randomseed(os.time())
    local random = math.random
    local template = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
    return string.gsub(template, "x", function()
      local v = random(0, 0xf)  -- v is a decimal number 0 to 15
      return string.format("%x", v) --formatted as a hex number
    end)

--[[ Generate a uuid and place it at current cursor position --]]
local insert_uuid = function()
    -- Get row and column cursor,
    -- use unpack because it's a tuple.
    local row, col = unpack(vim.api.nvim_win_get_cursor(0))
    local uuid = generate_uuid()
    -- Notice the uuid is given as an array parameter, you can pass multiple strings.
    -- Params 2-5 are for start and end of row and columns.
    -- See earlier docs for param clarification or `:help nvim_buf_set_text.
    vim.api.nvim_buf_set_text(0, row - 1, col, row - 1, col, { uuid })
end

-- Finally we map this somewhere to the key and mode we want.
-- i stands for insert mode next set the insert_uuid without invoking it.
-- For the last parameter see `:help map-arguments`  and adjust accordingly.
vim.keymap.set('i', '\\', insert_uuid, { noremap = true, silent = true })

Now uuid is placed when in insert mode when typing '\', consider changing this and/or using leader.

For mapping see docs on keys and docs on set command :help vim.keymap.set. The last one is in the online docs too but couldn't find it quickly. Afaik :help and online docs should contain the same info.

Besides the tips given in the docs concerning nvim_buf_set_text usage also consider looking at nvim_buf_get_lines() and nvim_buf_set_lines() for multiline operations.

This should work as desired.