How to prepend \<C-U> to vim.cmd API?

[linrongbin16]

Hi, I am writing a key map util function:

local function exec(op)
    if type(op) == "string" then
        -- vim command
        vim.cmd(op)
    else
        -- lua function
        op()
    end
end

local function map(mode, lhs, rhs, opts)
    opts = vim.tbl_deep_extend("force", {silent=true, noremap=true}, opts or {})
    vim.keymap.set(mode, lhs, rhs, opts)
end

-- here define some key mappings

map({'n', 'x'}, '<leader>f', exec('echo hello'))

But now, I have a specific requirement, that I want to get the block-wise visual selection. based on this: https://stackoverflow.com/a/61486601/4438921, I found that I have to use vimscript to define key mapping:

xnoremap <leader>f :\<C-U> call GetVisualSelection(visualmode())<cr>

How could I do it in lua?

[oncomouse]

I think vim.keymap.set({'x'}, ":<c-u> call GetVisualSelection(visualmode())<cr>") should work. You don't need to wrap rhs in that exec function inside of your map() function (which you also don't need). vim.keymap.set already correctly handles strings and functions passed to rhs.

[oncomouse]

With the command, you can call vim.cmd('FzfGrep'). With the other function, you can run vim.fn['fzf#vim#grep']()

[linrongbin16]

In that case, it seems I will miss the \<C-U>, thus I cannot get the correct block-wise visual selection?

[linrongbin16]

mayby I can try adding a normal! before calling the function: vim.cmd('normal! call getVisualSelection(visualmode())').

because based on another answer: https://stackoverflow.com/a/47051271/4438921, it says

`'<` and `'>` don't get updated when the user is still in visual mode.

That is the reason, that I cannot get the correct visual selection in getVisualSelection function.

But if now I try to add normal!, maybe it will first exit visual mode, then I can get the correct (e.g. the previous visual mode) visual selection

[TheLeoP]

In that case, it seems I will miss the <C-U>, thus I cannot get the correct block-wise visual selection?

In this context, those keys only delete '<,'> because it gets automatically inserted in the command line when you press : on visual mode. If you check :h c_ctrl-u you will see that this is what <c-u> does in command mode.

mayby I can try adding a normal! before calling the function: vim.cmd('normal! call getVisualSelection(visualmode())').
because based on another answer: https://stackoverflow.com/a/47051271/4438921, it says
'< and '> don't get updated when the user is still in visual mode.
That is the reason, that I cannot get the correct visual selection in getVisualSelection function.
But if now I try to add normal!, maybe it will first exit visual mode, then I can get the correct (e.g. the previous visual mode) visual selection

Yes, those marks are not set until you leave visual mode. But, \<c-u> has nothing to do with it, the thing that makes you leave visual mode in the vimscript mapping is : (because you enter command mode). So, if you wan't to force neovim to leave visual mode so the marks are set, you can use vim.cmd.normal('�') (where � is what neoivm sees when you press <esc>). The full function would be:

vim.keymap.set({ "x" }, "<leader>f", function()
  vim.cmd.normal "�"
  vim.fn.GetVisualSelection(vim.fn.visualmode())
end)

[linrongbin16]

Oh yes, what you said is really that I want!
BTW, can I use \<ESC> instead of �? I don't how to write it in my config.

[linrongbin16]

I tried <ESC> in this commit: linrongbin16/lin.nvim@f63d5b4

But there's an error message:

Looks like there's some escape char issue....

[linrongbin16]

Finally I fixed it in commit: linrongbin16/lin.nvim@86f929e