#1497 Tolerate important ALE variables being undefined for some reason when viewing buffers like git commits

autoload/ale.vim

@@ -33,6 +33,10 @@ endfunction
 
 " Return 1 if a file is too large for ALE to handle.
 function! ale#FileTooLarge() abort
+    if !exists('g:ale_maximum_file_size')
+        return 0
+    endif
+
     let l:max = ale#Var(bufnr(''), 'maximum_file_size')
 
     return l:max > 0 ? (line2byte(line('$') + 1) > l:max) : 0
@@ -46,13 +50,18 @@ function! ale#ShouldDoNothing(buffer) abort
     " The checks are split into separate if statements to make it possible to
     " profile each check individually with Vim's profiling tools.
 
+    " Do nothing if ALE is disabled.
+    if !getbufvar(a:buffer, 'ale_enabled', get(g:, 'ale_enabled', 0))
+        return 1
+    endif
+
     " Don't perform any checks when newer NeoVim versions are exiting.
     if get(v:, 'exiting', v:null) isnot v:null
         return 1
     endif
 
     " Do nothing for blacklisted files
-    if index(g:ale_filetype_blacklist, getbufvar(a:buffer, '&filetype')) >= 0
+    if index(get(g:, 'ale_filetype_blacklist', []), getbufvar(a:buffer, '&filetype')) >= 0
         return 1
     endif
 
@@ -72,11 +81,6 @@ function! ale#ShouldDoNothing(buffer) abort
         return 1
     endif
 
-    " Do nothing if ALE is disabled.
-    if !ale#Var(a:buffer, 'enabled')
-        return 1
-    endif
-
     " Do nothing if the file is too large.
     if ale#FileTooLarge()
         return 1

test/test_lint_error_delay.vader

@@ -1,11 +1,13 @@
 Before:
-  Save g:ale_filetype_blacklist
+  runtime autoload/ale.vim
 
-  " Delete some variable which should be defined.
-  unlet! g:ale_filetype_blacklist
+  " Replace one of the key ALE functions and make it throw.
+  function! ale#FileTooLarge() abort
+    throw 'broken'
+  endfunction
 
 After:
-  Restore
+  runtime autoload/ale.vim
 
   call ale#ResetErrorDelays()
 

test/test_should_do_nothing_conditions.vader

@@ -1,4 +1,7 @@
 Before:
+  Save g:ale_filetype_blacklist
+  Save g:ale_maximum_file_size
+  Save g:ale_enabled
   Save &l:statusline
 
   call ale#test#SetDirectory('/testplugin/test')
@@ -12,6 +15,8 @@ Before:
   endif
 
 After:
+  Restore
+
   call ale#test#RestoreDirectory()
 
   if b:funky_command_created
@@ -21,8 +26,6 @@ After:
 
   unlet! b:funky_command_created
 
-  Restore
-
 Execute(ALE shouldn't do much of anything for ctrlp-funky buffers):
   Assert !ale#ShouldDoNothing(bufnr('')), 'The preliminary check failed'
 
@@ -39,3 +42,11 @@ Execute(ALE shouldn't try to check buffers with '.' as the filename):
   silent! noautocmd file .
 
   Assert ale#ShouldDoNothing(bufnr(''))
+
+Execute(The DoNothing check should work if the ALE globals aren't defined):
+  unlet! g:ale_filetype_blacklist
+  unlet! g:ale_maximum_file_size
+  unlet! g:ale_enabled
+
+  " This shouldn't throw exceptions.
+  call ale#ShouldDoNothing(bufnr(''))