:checkhealth : validate $VIM

runtime/autoload/health/nvim.vim

@@ -4,12 +4,19 @@ function! s:check_config() abort
   let ok = v:true
   call health#report_start('Configuration')
 
+  " 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: ".$VIM)
+  endif
+
   if exists('$NVIM_TUI_ENABLE_CURSOR_SHAPE')
     let ok = v:false
     call health#report_warn("$NVIM_TUI_ENABLE_CURSOR_SHAPE is ignored in Nvim 0.2+",
           \ [ "Use the 'guicursor' option to configure cursor shape. :help 'guicursor'",
           \   'https://github.com/neovim/neovim/wiki/Following-HEAD#20170402' ])
   endif
+
   if &paste
     let ok = v:false
     call health#report_error("'paste' is enabled. This option is only for pasting text.\nIt should not be set in your config.",

test/functional/plugin/health_spec.lua

@@ -3,6 +3,7 @@ local Screen = require('test.functional.ui.screen')
 local plugin_helpers = require('test.functional.plugin.helpers')
 
 local clear = helpers.clear
+local curbuf_contents = helpers.curbuf_contents
 local command = helpers.command
 local eq = helpers.eq
 
@@ -16,13 +17,12 @@ describe(':checkhealth', function()
     eq('Invalid $VIMRUNTIME: bogus', string.match(err, 'Invalid.*'))
   end)
   it("detects invalid $VIM", function()
-    clear({
-      env={ VIM='bogus', },
-    })
-    local status, err = pcall(command, 'checkhealth')
-    eq(false, status)
-    -- Invalid $VIM causes $VIMRUNTIME to be broken.
-    eq('Invalid $VIMRUNTIME: bogus', string.match(err, 'Invalid.*'))
+    clear()
+    -- Do this after startup, otherwise it just breaks $VIMRUNTIME.
+    command("let $VIM='zub'")
+    command("checkhealth nvim")
+    eq("ERROR: $VIM is invalid: zub",
+       string.match(curbuf_contents(), "ERROR: $VIM .* zub"))
   end)
 end)