How to check if an autoload function exists without calling it?

Question

Say I have vim-plug installed

But before calling call plug#begin(), I want to check if this function exists

How to perform this check?

I tried the following:

echom empty(g:plug)
echom empty(plug)
echom empty(plug#begin)

But all of the above led to an "Undefined variable" error, although the function was defined and calling it was successful.

Answer 1

For a function specifically, you can write

if exists('*funcname')
  …
endif

(that would be exists('*plug#begin') here). More generally, see the documentation for :help exists().

Answer 2

This is an autoloaded function, so you can't (because it just did not exist until it has been loaded successfully).

If you really believe you need to check that then do it by try and catch.

Answer 3

As this is a function from an autoload plugin, you need first to be sure the plugin has been loaded before checking for the function. This means the typical sequence (if you're not sure the plugin is installed!) would be

runtime autoload/plug.vim  " because the function is plug#something()
if exists('*plug#begin')
   whatever you want to do with it
endif