`nvim-mapper`

nvim-mapper provides wrappers around vim.keymap.set which allows you to pass through a callback for the right side of you keymap which gets fed the previous mapping as an argument so you can use it as a fallback in your new mapping.

Installation

Regular lazy installation. No setup required as you are just importing and using the function to map your key:

{ "kamalsacranie/nvim-mapper" }

Usage

Sometimes I want to multiple things one key can do depending on some conditions. For example, in insert mode, I want <C-f> to jump me forward in my snippet, if there is text on the line, I want it to put me at the end of my line, and finally, if the line is empty, I want it to indent my cursor to the correct position (the default behavour). nvim-mapper allows me to do this.

Let's say I define the following mappings, in this order, with nvim-mapper:

-- jumps my cursor to the end of the line if there is text on the line
require("nvim-mapper").map_keymap("i", "<C-f>", function(fallback)
    if vim.fn.len(vim.fn.getline(".")) > vim.fn.getpos(".")[3] then
        return "<C-o>$"
    else
        fallback()
    end
end)

Note if I just wanted to map <C-f> to <C-o>\$, I would just put the raw string in the 3rd argument of map_keymap. fallback is the default behaviour vim has for using that mapping. In the case of <C-f>, it indents our cursor at the correct line in our current scope. Note also that we return the string which must be done otherwise the keys won't be sent to neovim

Then let's define a function which jumps our cursor forward if we are in a luasnippet.

local ls = require("luasnip")
require("nvim-mapper").map_keymap({ "i", "s" }, "<C-f>", function(fallback)
    if ls.jumpable(1) then
        return ls.jump(1)
    else
        fallback()
    end
end)

As long as these are defined in the correct order, now we have a keymap which does the following:

If we are in a snippet, we jump
If we are on a line with characters, we jump to the end of the line
If we are on a blank line, we indent our cursor

Points to note

map_keymap takes the same arguments as vim.keymap.set so it's pretty my an in place substituion
Because of the way I am passign through the fallback argument, the fallback function MUST BE anonymous. I.e., you must define it in the argument place and not define it before you call map_keymap
You also have a convenience fucntions to map multiple keymaps at once map_keymap_list which does exactly what you think it does