2 files changed, 32 insertions, 13 deletions
diff --git a/vim/autoload/getenv.vim b/vim/autoload/getenv.vim
new file mode 100644
index 00000000..2b8fef1b
--- /dev/null
+++ b/vim/autoload/getenv.vim
@@ -0,0 +1,22 @@
+" Backport getenv() from v8.1.1305
+"
+" <https://github.com/vim/vim/releases/tag/v8.1.1305>
+"
+function! getenv#(name) abort
+
+  " Use native if available
+  if exists('*getenv')
+    return getenv(a:name)
+  endif
+
+  " Backport
+  if a:name !~# '^[A-Z][A-Z0-9_]*$'
+    throw 'Illegal env var name'
+  endif
+  let value = v:null
+  if exists('$'.a:name)
+    execute 'let value = $'.a:name
+  endif
+  return value
+
+endfunction
diff --git a/vim/autoload/xdg.vim b/vim/autoload/xdg.vim
index 2b1e7c56..2b90f5f1 100644
--- a/vim/autoload/xdg.vim
+++ b/vim/autoload/xdg.vim
@@ -11,28 +11,25 @@ let s:subdir = 'vim'
 
 function! s:Get(name) abort
   let name = a:name
-  if name !~# '^[A-Z][A-Z0-9_]*$'
-    throw 'Illegal env var name'
-  endif
-  let value = ''
-  execute 'let value = $'.name
-  if value !=# ''
-    return value
-  elseif has_key(s:defaults, name)
-    return s:defaults[name]
-  else
-    return ''
+  if !has_key(s:defaults, name)
+    throw 'Illegal XDG basedirs env var name'
   endif
+  let value = getenv#(name)
+  return value !=# v:null
+        \ ? value
+        \ : s:defaults[name]
 endfunction
 
 function! s:Absolute(path) abort
-  return a:path =~# '^[/~]'
+  return a:path =~# '^/'
+        \ || a:path =~# '^\~/'
+        \ || a:path ==# '~'
 endfunction
 
 function! s:Home(name) abort
   let home = s:Get(a:name)
   if !s:Absolute(home)
-    return ''
+    return v:null
   endif
   return join([home, s:subdir], '/')
 endfunction