How to set keywordprg to call a lua function in neovim?

Question

A plugin unidentified is setting the keywordprg option to :Man but I want it to be LSP based.

So I attempted

set keywordprg=:lua\ vim.lsp.buf.signature_help()

but it gives me the following error and I press K on a NOTE: it for some reason works with vimls but not with pyright of rust-analyzer keyword:

E5107: Error loading lua [string ":lua"]:1: '=' expected near '<eof>'

So how may I fix this error?

Answer 1

The 'keywordprg' setting can take an Ex command (starting with :), but when it does, the Ex command needs to be able to take an argument, and you can't pass one to a Lua function using :lua that way.

The simplest way around this is to define a new user-defined command that calls the LSP function with the passed arguments and then use that in 'keywordprg'.

In your case of calling one of the LSP functions, it's a bit odd that those take into consideration the current location, rather than getting an argument with the term to look up... One alternative here would be to have the user-defined command just ignore its arguments and simply call the LSP function with no arguments at all.

For example:

command -nargs=+ LspHover lua vim.lsp.buf.hover()

And then you could use:

set keywordprg=:LspHover