Show how to call :echom / do print debugging about nvim-lua-guide

[nanotee]

Looking at :help lua-commands, the built-in print() function is wired to the message area instead of standard output:

The Lua print() function redirects its output to the Nvim message area, with
arguments separated by " " (space) instead of "\t" (tab).

This isn't immediately obvious from reading the guide though, and people might want to test that everything is working correctly. I'll add a short paragraph about this, thank you for the suggestion!

[Julian]

Interesting -- print was the first thing I tried and didn't see the output in :messages, but that likely instead means the thing I tried was indeed not running :D

And yeah thanks for writing this!

[clason]

One small gotcha people might not expect is that a silent! in a command also prevents Lua print output. So

nnoremap silent! <leader>l :lua print('foo')<cr>

in fact prints nothing when entering <leader>l.

[nanotee]

@clason Did you mean nnoremap <silent>? I did a few tests and both of these mappings seem to be equivalent:

nnoremap <silent> <leader>l :echomsg 'foo'<CR> " prints 'foo'
nnoremap <silent> <leader>l :lua print('foo')<CR> " prints 'foo'

[clason]

No, I meant what I wrote (:h silent). It may in fact not be very surprising, although I have repeatedly added debug print statements to Lua functions I call via silent! and then wondered why I didn't see that output (because I didn't connect the vimscript command with the Lua function)...