Checkhealth - ERROR: $VIM is invalid: $HOME/.config/vim

Question

I share most of the configuration for vim and neovim between them and I set $VIM like this…

if has('unix')
  let $VIM = "$HOME/.config/vim"
elseif has('win32')
  let $VIM = "$HOME/vimfiles"
endif

…which makes it possible to set file paths elsewhere throughout the configuration for both Linux and Windows without using conditional statements (in most cases, but not all).

According to :h $VIM this is fine and pretty much the intended purpose of the variable. So why does :checkhealth give this error message in the new version of nvim (0.8.0)?

## Configuration                                                                                                                                                                                                                                                                                                                                                  
  - ERROR: $VIM is invalid: $HOME/.config/vim

Answer 1

The health of $VIM variable is checked with the following logic¹:

" If $VIM is empty we don't care. Else make sure it is valid.
if !empty($VIM) && !filereadable($VIM.'/runtime/doc/nvim.txt')
  let ok = v:false
  call health#report_error('$VIM is invalid: '.$VIM)
endif

You must not have $HOME/.config/vim/runtime/doc/nvim.txt, or if you have it, you must not have read-permission for that file (the latter case is highly unlikely). That's the reason for the error you're facing.

## Configuration
  - ERROR: $VIM is invalid: $HOME/.config/vim

---

The logic above tells us that $VIM is expected to point to the directory where vim's system files reside. As for the reason behind, a look at the nvim source code reveals that the environment variable $VIM is accessed only twice in the who codebase.

• To set system vimrc file²
• When checking for $VIMRUNTIME and finding it nil³.

($VIM is also handled when you do :echo $VIM, but that comes later in the execution time, and by then both $VIM and $VIMRUNTIME and most if not all variables have been set already.)

So, if we've got our own vimrc file (which means vim won't need the system vimrc) and we've set $VIMRUNTIME properly (pointing to where vim's system runtime files exist), then the value of $VIM should invite no complication. We can simply ignore the error put out by :checkhealth.

BUT if we've not set $VIMRUNTIME and have set $VIM to an arbitrary location, then the value of $VIMRUNTIME will be set wrongly at startup. See the stacktrace at the startup on a breakpoint at vim_getenv³.

gdb> where
#0  vim_getenv (name=0x7ff6f47638b9 <__func__.2+969> "VIMRUNTIME") at E:/projects/neovim/master/src/nvim/os/env.c:901
#1  0x00007ff6f44d62da in runtimepath_default (clean_arg=false) at E:/projects/neovim/master/src/nvim/runtime.c:1511
#2  0x00007ff6f446720f in set_init_1 (clean_arg=false) at E:/projects/neovim/master/src/nvim/option.c:316
#3  0x00007ff6f43ea95e in early_init (paramp=0x850f1ff530) at E:/projects/neovim/master/src/nvim/main.c:201
#4  0x00007ff6f43eab4d in wmain (argc=1, argv_w=0x22b48aa44b0) at E:/projects/neovim/master/src/nvim/main.c:257
#5  0x00007ff6f42513da in __tmainCRTStartup () at C:/M/mingw-w64-crt-git/src/mingw-w64/mingw-w64-crt/crt/crtexe.c:326
#6  0x00007ff6f4251506 in mainCRTStartup () at C:/M/mingw-w64-crt-git/src/mingw-w64/mingw-w64-crt/crt/crtexe.c:206

It's this case that will cause problems such as vim not finding syntax file ($VIMRUNTIME/syntax/syntax.vim), etc. Otherwise, we can use $VIM as our own personal environment variable.

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