#274 - Fix airline integration when ALE is not loaded fully

autoload/ale/statusline.vim

@@ -3,6 +3,10 @@
 
 " Update the buffer error/warning count with data from loclist.
 function! ale#statusline#Update(buffer, loclist) abort
+    if !exists('g:ale_buffer_info')
+        return
+    endif
+
     if !has_key(g:ale_buffer_info, a:buffer)
         return
     endif
@@ -39,6 +43,10 @@ endfunction
 
 " Returns a tuple of errors and warnings for use in third-party integrations.
 function! ale#statusline#Count(buffer) abort
+    if !exists('g:ale_buffer_info')
+        return [0, 0]
+    endif
+
     if !s:SetupCount(a:buffer)
         return [0, 0]
     endif
@@ -48,6 +56,10 @@ endfunction
 
 " Returns a formatted string that can be integrated in the statusline.
 function! ale#statusline#Status() abort
+    if !exists('g:ale_buffer_info')
+        return 'OK'
+    endif
+
     let [l:error_format, l:warning_format, l:no_errors] = g:ale_statusline_format
     let l:buffer = bufnr('%')
 

test/test_statusline_api_without_globals.vader

@@ -0,0 +1,19 @@
+" This file tests that statusline functions return meaningful output even
+" when most of ALE itself has not been loaded.
+"
+" This is important for plugins which integrate with ALE like airline.
+
+Before:
+  unlet! g:ale_buffer_info
+
+After:
+  let g:ale_buffer_info = {}
+
+Execute(ale#statusline#Update shouldn't blow up when globals are undefined):
+  call ale#statusline#Update(1, [])
+
+Execute(ale#statusline#Count should return 0 counts when globals are undefined):
+  AssertEqual [0, 0], ale#statusline#Count(1)
+
+Execute(ale#statusline#Status should return 'OK' when globals are undefined):
+  AssertEqual 'OK', ale#statusline#Status()