Use ModeChanged events instead of InsertLeave emulation #4919 #4738

`ModeChanged` looks like a more reliable way to detect an "exit insert mode" event and is a lot simpler (doesn't need a timer). Also, it can detect some other transitions like `\<C-o\>` in insert mode.
The `ModeChanged` event is available in:

* [Vim 8.2.3430](f1e8876fa2)
* [NeoVim 0.7.0](69bd1e4e36)

---------

Co-authored-by: Dmitry Zolotukhin <zlogic@gmail.com>

autoload/ale/events.vim

@@ -100,6 +100,10 @@ if !exists('s:insert_leave_timer')
     let s:insert_leave_timer = -1
 endif
 
+" True if the ModeChanged event exists.
+" In this case, ModeChanged will be used instead of InsertLeave emulation.
+let s:mode_changed_exists = exists('##ModeChanged')
+
 function! ale#events#EmulateInsertLeave(buffer) abort
     if mode() is# 'n'
         call timer_stop(s:insert_leave_timer)
@@ -114,8 +118,12 @@ function! ale#events#InsertEnterEvent(buffer) abort
 
     " Start a repeating timer if the use might not trigger InsertLeave, so we
     " can emulate its behavior.
+    " If the ModeChanged autocmd exists, it will be used instead of this
+    " timer; as ModeChanged will be sent regardless of how the insert mode is
+    " exited, including <Esc>, <C-c> and <C-]>.
     if ale#Var(a:buffer, 'lint_on_insert_leave')
     \&& maparg("\<C-c>", 'i') isnot# '<Esc>'
+    \&& !s:mode_changed_exists
         call timer_stop(s:insert_leave_timer)
         let s:insert_leave_timer = timer_start(
         \   100,
@@ -126,10 +134,15 @@ function! ale#events#InsertEnterEvent(buffer) abort
 endfunction
 
 function! ale#events#InsertLeaveEvent(buffer) abort
-    if ale#Var(a:buffer, 'lint_on_insert_leave')
     " Kill the InsertLeave emulation if the event fired.
+    " If the ModeChanged event is available, it will be used instead of
+    " a timer.
+    if !s:mode_changed_exists
         call timer_stop(s:insert_leave_timer)
-        call ale#Queue(0)
+    endif
+
+    if ale#Var(a:buffer, 'lint_on_insert_leave')
+        call ale#Queue(0, '', a:buffer)
     endif
 
     " Look for a warning to echo as soon as we leave Insert mode.
@@ -189,8 +202,11 @@ function! ale#events#Init() abort
             "
             " We will emulate leaving insert mode for users that might not
             " trigger InsertLeave.
+            "
+            " If the ModeChanged event is available, this timer will not
+            " be used.
             if g:ale_close_preview_on_insert
-            \|| (g:ale_lint_on_insert_leave && maparg("\<C-c>", 'i') isnot# '<Esc>')
+            \|| (g:ale_lint_on_insert_leave && maparg("\<C-c>", 'i') isnot# '<Esc>' && !s:mode_changed_exists)
                 autocmd InsertEnter * call ale#events#InsertEnterEvent(str2nr(expand('<abuf>')))
             endif
 
@@ -211,8 +227,15 @@ function! ale#events#Init() abort
             endif
 
             if l:add_insert_leave_event
+                if s:mode_changed_exists
+                    " If the ModeChanged event is available, handle any
+                    " transition from the Insert mode to any other mode.
+                    autocmd ModeChanged i*:* call ale#events#InsertLeaveEvent(str2nr(expand('<abuf>')))
+                else
+                    " If ModeChanged is not available, handle InsertLeave events.
                     autocmd InsertLeave * call ale#events#InsertLeaveEvent(str2nr(expand('<abuf>')))
                 endif
+            endif
 
             if g:ale_hover_cursor
                 autocmd CursorHold * if exists('*ale#lsp#Send') | call ale#hover#ShowTruncatedMessageAtCursor() | endif

test/test_autocmd_commands.vader

@@ -94,11 +94,17 @@ Execute (All events should be set up when everything is on):
   \   'FileChangedShellPost * call ale#events#FileChangedEvent(str2nr(expand(''<abuf>'')))',
   \   'FileType * call ale#events#FileTypeEvent( str2nr(expand(''<abuf>'')), expand(''<amatch>''))',
   \ ] + (
-  \   maparg("\<C-c>", 'i') isnot# '<Esc>'
-  \     ? ['InsertEnter * call ale#events#InsertEnterEvent(str2nr(expand(''<abuf>'')))']
+  \   maparg("\<C-c>", 'i') isnot# '<Esc>' && !exists('##ModeChanged')
+  \     ? [
+  \         'InsertEnter * call ale#events#InsertEnterEvent(str2nr(expand(''<abuf>'')))',
+  \         'InsertLeave * call ale#events#InsertLeaveEvent(str2nr(expand(''<abuf>'')))',
+  \       ]
+  \     : []
+  \ ) + (
+  \   exists('##ModeChanged')
+  \     ? ['ModeChanged i*:* call ale#events#InsertLeaveEvent(str2nr(expand(''<abuf>'')))']
   \     : []
   \ ) + [
-  \   'InsertLeave * call ale#events#InsertLeaveEvent(str2nr(expand(''<abuf>'')))',
   \   'TextChanged * call ale#Queue(ale#Var(str2nr(expand(''<abuf>'')), ''lint_delay''))',
   \   'TextChangedI * call ale#Queue(ale#Var(str2nr(expand(''<abuf>'')), ''lint_delay''))',
   \ ],
@@ -185,25 +191,40 @@ Execute (g:ale_lint_on_text_changed = 'insert' should bind only TextChangedI):
   \ ],
   \ filter(CheckAutocmd('ALEEvents'), 'v:val =~ ''^TextChanged''')
 
-Execute (g:ale_lint_on_insert_leave = 1 should bind InsertLeave):
+Execute (g:ale_lint_on_insert_leave = 1 should bind InsertLeave or ModeChanged if available):
   let g:ale_lint_on_insert_leave = 1
   let g:ale_echo_cursor = 0
 
   " CI at least should run this check.
   " There isn't an easy way to save an restore a mapping during running the test.
-  if maparg("\<C-c>", 'i') isnot# '<Esc>'
+  if maparg("\<C-c>", 'i') isnot# '<Esc>' && !exists('##ModeChanged')
     AssertEqual
     \ [
     \   'InsertEnter * call ale#events#InsertEnterEvent(str2nr(expand(''<abuf>'')))',
     \ ],
     \ filter(CheckAutocmd('ALEEvents'), 'v:val =~ ''^InsertEnter''')
+  else
+    " If the ModeChanged event is available, starting the timer in InsertEnter is not necessary.
+    AssertEqual
+    \ [
+    \ ],
+    \ filter(CheckAutocmd('ALEEvents'), 'v:val =~ ''^InsertEnter''')
   endif
 
+  if !exists('##ModeChanged')
+    " If the ModeChanged event is not available, bind InsertLeave.
     AssertEqual
     \ [
     \   'InsertLeave * call ale#events#InsertLeaveEvent(str2nr(expand(''<abuf>'')))',
     \ ],
     \ filter(CheckAutocmd('ALEEvents'), 'v:val =~ ''^InsertLeave''')
+  else
+    AssertEqual
+    \ [
+    \   'ModeChanged i*:* call ale#events#InsertLeaveEvent(str2nr(expand(''<abuf>'')))',
+    \ ],
+    \ filter(CheckAutocmd('ALEEvents'), 'v:val =~ ''^ModeChanged''')
+  endif
 
 Execute (g:ale_lint_on_filetype_changed = 1 should bind the FileType event):
   let g:ale_lint_on_filetype_changed = 1

test/test_cursor_warnings.vader

@@ -158,9 +158,9 @@ Execute(The message at the cursor should be shown when linting ends):
 
   AssertEqual 'semi: Missing semicolon.', g:last_message
 
-Execute(The message at the cursor should be shown on InsertLeave):
+Execute(The message at the cursor should be shown when leaving insert mode):
   call cursor(2, 9)
-  doautocmd InsertLeave
+  call feedkeys("i\<Esc>", 'tnix')
 
   AssertEqual 'space-infix-ops: Infix operators must be spaced.', g:last_message