Functions builtin.file and builtin.file_relative return full path

[PanagiotisS]

Problems summary

The functions builtin.file and builtin.file_relative return the full path.

I do not know if this intentional, however, given that builtin.file_relative = builtin.file, I assume that we would like the relative path, similar to statusline=%f, as also the line commented line 12 hints.

If the above assumption is wrong, please ignore and close the report.

Environment Information

• neovim version: neovim-0.4.4.0.git.14889.c6ccdda26 -> neovim/neovim@c6ccdda

• plenary version: nvim-lua/plenary.nvim@c8287c3

• express_line version: 903dc60

Minimal init.vim

set encoding=utf-8
scriptencoding utf-8

" Dein 
let s:path = expand(stdpath('config') . '/bundle')
let &runtimepath .= ',' . expand(stdpath('config') . '/bundle/repos/github.com/Shougo/dein.vim/')

if dein#load_state(s:path)
    call dein#begin(s:path, [expand('<sfile>'),])

    call dein#add('Shougo/dein.vim',)

    call dein#add('nvim-lua/plenary.nvim')

    call dein#add('tjdevries/express_line.nvim')

    call dein#end()
    call dein#save_state()
endif

filetype plugin indent on
syntax enable

set number
set nowrap
set bg=light

lua << EOF
local generator = function()
    local el_segments = {}

    -- This will return the full path - see screenshot 1
    local builtin = require('el.builtin')
    table.insert(el_segments, builtin.file)

    -- This will return the relative path - see screenshot 2
    -- table.insert(el_segments, '%f')

    return el_segments
end
-- The setup is commented so I can call each setup each time
--  to ensure that the screenshot contains all the relevant information
-- require('el').setup{generator = generator}
EOF

How to reproduce the problem

Screenshot 1 (problematic case)

Using table.insert(el_segments, builtin.file)

Screenshot 2 (OK)

Using table.insert(el_segments, '%f')

Screenshot 3 (OK)

Using set statusline=%f

Screenshot 4 (OK)

Using table.insert(el_segments, builtin.full_file)

Screenshot 5 (OK)

Using table.insert(el_segments, '%F')

Screenshot 6 (OK)

Using set statusline=%F

We would expect cases/screenshots 1, 2, and 3 to have the same result in the same way as cases/screenshots 4, 5, and 6 have the same result.

Well, cases/screenshots 4, 5, and 6 have a difference that the home path is displayed in full using full_file and with ~ when using %f so not exactly the same.

Discussion

My knowledge of lua is limited so here we go,

The function builtin.file is using buffer.name (if buffer.name is not empty).

The buffer.name is set using nvim_buf_get_name.

However, nvim_buf_get_name returns the full path.
In the above example using :lua print(vim.api.nvim_buf_get_name(0)) returns /home/ps/Documents/codes/python/empty.py

Using :help nvim_buf_get_name or looking at the source code we have /// Gets the full file name for the buffer.
I assume what here full file name means is the file name including the full path.

In contrast, :help buffname returns the name of the file using the relative path.