Set up one BufEnter event used for everything, and add tests for linting when the filetype changes

autoload/ale/events.vim

@@ -24,9 +24,20 @@ function! s:LintOnEnter(buffer) abort
 endfunction
 
 function! ale#events#EnterEvent(buffer) abort
+    let l:filetype = getbufvar(a:buffer, '&filetype')
+    call setbufvar(a:buffer, 'ale_original_filetype', l:filetype)
+
     call s:LintOnEnter(a:buffer)
 endfunction
 
+function! ale#events#FileTypeEvent(buffer, new_filetype) abort
+    let l:filetype = getbufvar(a:buffer, 'ale_original_filetype', '')
+
+    if a:new_filetype isnot# l:filetype
+        call ale#Queue(300, 'lint_file', a:buffer)
+    endif
+endfunction
+
 function! ale#events#FileChangedEvent(buffer) abort
     call setbufvar(a:buffer, 'ale_file_changed', 1)
 

plugin/ale.vim

@@ -218,27 +218,26 @@ function! ALEInitAuGroups() abort
 
     augroup ALERunOnEnterGroup
         autocmd!
+        if g:ale_enabled
+            " Handle everything that needs to happen when buffers are entered.
+            autocmd BufEnter * call ale#events#EnterEvent(str2nr(expand('<abuf>')))
+        endif
         if g:ale_enabled && g:ale_lint_on_enter
             autocmd BufWinEnter,BufRead * call ale#Queue(0, 'lint_file', str2nr(expand('<abuf>')))
             " Track when the file is changed outside of Vim.
             autocmd FileChangedShellPost * call ale#events#FileChangedEvent(str2nr(expand('<abuf>')))
-            " If the file has been changed, then check it again on enter.
-            autocmd BufEnter * call ale#events#EnterEvent(str2nr(expand('<abuf>')))
         endif
     augroup END
 
     augroup ALERunOnFiletypeChangeGroup
         autocmd!
         if g:ale_enabled && g:ale_lint_on_filetype_changed
-            " Set the filetype after a buffer is opened or read.
-            autocmd BufEnter,BufRead * let b:ale_original_filetype = &filetype
             " Only start linting if the FileType actually changes after
             " opening a buffer. The FileType will fire when buffers are opened.
-            autocmd FileType *
+            autocmd FileType * call ale#events#FileTypeEvent(
-            \   if has_key(b:, 'ale_original_filetype')
+            \   str2nr(expand('<abuf>')),
-            \   && b:ale_original_filetype isnot# expand('<amatch>')
+            \   expand('<amatch>')
-            \|      call ale#Queue(300, 'lint_file')
+            \)
-            \|  endif
         endif
     augroup END
 

test/test_ale_init_au_groups.vader

@@ -107,10 +107,12 @@ Execute (g:ale_pattern_options_enabled = 1 should bind BufReadPost and BufEnter)
   \ 'BufReadPost * call ale#pattern_options#SetOptions()',
   \], CheckAutocmd('ALEPatternOptionsGroup')
 
-Execute (g:ale_lint_on_enter = 0 should bind no events):
+Execute (g:ale_lint_on_enter = 0 should bind only the BufEnter event):
   let g:ale_lint_on_enter = 0
 
-  AssertEqual [], CheckAutocmd('ALERunOnEnterGroup')
+  AssertEqual
+  \ ['BufEnter * call ale#events#EnterEvent(str2nr(expand(''<abuf>'')))'],
+  \ CheckAutocmd('ALERunOnEnterGroup')
 
 Execute (g:ale_lint_on_enter = 1 should bind the required events):
   let g:ale_lint_on_enter = 1
@@ -127,18 +129,17 @@ Execute (g:ale_lint_on_filetype_changed = 0 should bind no events):
 
   AssertEqual [], CheckAutocmd('ALERunOnFiletypeChangeGroup')
 
-Execute (g:ale_lint_on_filetype_changed = 1 should bind FileType, and required buffer events):
+Execute (g:ale_lint_on_filetype_changed = 1 should bind the FileType event):
   let g:ale_lint_on_filetype_changed = 1
 
-  AssertEqual [
+  AssertEqual
-  \ 'BufEnter * let b:ale_original_filetype = &filetype',
+  \ [
-  \ 'BufReadPost * let b:ale_original_filetype = &filetype',
+  \   'FileType * call ale#events#FileTypeEvent( '
-  \ 'FileType * '
+  \     . 'str2nr(expand(''<abuf>'')), '
-  \   . 'if has_key(b:, ''ale_original_filetype'') '
+  \     . 'expand(''<amatch>'')'
-  \   . '&& b:ale_original_filetype isnot# expand(''<amatch>'')'
+  \     . ')',
-  \   . '| call ale#Queue(300, ''lint_file'')'
+  \ ],
-  \   . '| endif',
+  \ CheckAutocmd('ALERunOnFiletypeChangeGroup')
-  \], CheckAutocmd('ALERunOnFiletypeChangeGroup')
 
 Execute (g:ale_lint_on_save = 0 should bind no events):
   let g:ale_lint_on_save = 0

test/test_lint_on_filetype_changed.vader

@@ -0,0 +1,47 @@
+Before:
+  Save &filetype
+
+  let g:queue_calls = []
+
+  function! ale#Queue(...)
+    call add(g:queue_calls, a:000)
+  endfunction
+
+After:
+  Restore
+
+  unlet! g:queue_calls
+
+  " Reload the ALE code to load the real function again.
+  runtime autoload/ale.vim
+
+  unlet! b:ale_original_filetype
+
+Execute(The original filetype should be set on BufEnter):
+  let &filetype = 'foobar'
+
+  call ale#events#EnterEvent(bufnr(''))
+
+  AssertEqual 'foobar', b:ale_original_filetype
+
+  let &filetype = 'bazboz'
+
+  call ale#events#EnterEvent(bufnr(''))
+
+  AssertEqual 'bazboz', b:ale_original_filetype
+
+Execute(Linting should not be queued when the filetype is the same):
+  let b:ale_original_filetype = 'foobar'
+  let g:queue_calls = []
+
+  call ale#events#FileTypeEvent(bufnr(''), 'foobar')
+
+  AssertEqual [], g:queue_calls
+
+Execute(Linting should be queued when the filetype changes):
+  let b:ale_original_filetype = 'foobar'
+  let g:queue_calls = []
+
+  call ale#events#FileTypeEvent(bufnr(''), 'bazboz')
+
+  AssertEqual [[300, 'lint_file', bufnr('')]], g:queue_calls

test/test_results_not_cleared_when_opening_loclist.vader

@@ -26,6 +26,9 @@ After:
   delfunction TestCallback
   let g:ale_buffer_info = {}
   call ale#linter#Reset()
+  call setloclist(0, [])
+  call clearmatches()
+  sign unplace *
 
 Given foobar (Some file):
   abc

test/test_setting_loclist_from_another_buffer.vader

@@ -1,8 +1,14 @@
 Before:
+  Save g:ale_buffer_info
+
+  let g:ale_buffer_info = {}
+
   let g:original_buffer = bufnr('%')
-  new
+  noautocmd new
 
 After:
+  Restore
+
   unlet! g:original_buffer
 
 Execute(Errors should be set in the loclist for the original buffer, not the new one):