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

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 [
-  \ 'BufEnter * let b:ale_original_filetype = &filetype',
-  \ 'BufReadPost * let b:ale_original_filetype = &filetype',
-  \ 'FileType * '
-  \   . 'if has_key(b:, ''ale_original_filetype'') '
-  \   . '&& b:ale_original_filetype isnot# expand(''<amatch>'')'
-  \   . '| call ale#Queue(300, ''lint_file'')'
-  \   . '| endif',
-  \], CheckAutocmd('ALERunOnFiletypeChangeGroup')
+  AssertEqual
+  \ [
+  \   'FileType * call ale#events#FileTypeEvent( '
+  \     . 'str2nr(expand(''<abuf>'')), '
+  \     . 'expand(''<amatch>'')'
+  \     . ')',
+  \ ],
+  \ 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):