vim-patch:8.2.0116: BufEnter autocmd not triggered on ":tab drop"

Problem:    BufEnter autocmd not triggered on ":tab drop". (Andy Stewart)
Solution:   Decrement autocmd_no_enter for the last file. (closes vim/vim#1660,
            closes vim/vim#5473)
c10b521628

N/A patches for version.c:

vim-patch:8.1.1805: au_did_filetype is declared twice

Problem:    Au_did_filetype is declared twice.
Solution:   Remove it from autocmd.c. (closes vim/vim#4767)
6cd57d4466

src/nvim/buffer.c

@@ -4706,7 +4706,6 @@ do_arg_all(
     int keep_tabs                 // keep current tabs, for ":tab drop file"
 )
 {
-  int i;
   char_u      *opened;          // Array of weight for which args are open:
                                 //  0: not opened
                                 //  1: opened in other tab
@@ -4715,6 +4714,7 @@ do_arg_all(
 
   int opened_len;               // length of opened[]
   int use_firstwin = false;     // use first window for arglist
+  bool tab_drop_empty_window = false;
   int split_ret = OK;
   bool p_ea_save;
   alist_T     *alist;           // argument list to be used
@@ -4762,6 +4762,7 @@ do_arg_all(
     win_T *wpnext = NULL;
     tpnext = curtab->tp_next;
     for (win_T *wp = firstwin; wp != NULL; wp = wpnext) {
+      int i;
       wpnext = wp->w_next;
       buf = wp->w_buffer;
       if (buf->b_ffname == NULL
@@ -4867,14 +4868,15 @@ do_arg_all(
   last_curwin = curwin;
   last_curtab = curtab;
   win_enter(lastwin, false);
-  // ":drop all" should re-use an empty window to avoid "--remote-tab"
+  // ":tab drop file" should re-use an empty window to avoid "--remote-tab"
   // leaving an empty tab page when executed locally.
   if (keep_tabs && BUFEMPTY() && curbuf->b_nwindows == 1
       && curbuf->b_ffname == NULL && !curbuf->b_changed) {
     use_firstwin = true;
+    tab_drop_empty_window = true;
   }
 
-  for (i = 0; i < count && i < opened_len && !got_int; i++) {
+  for (int i = 0; i < count && !got_int; i++) {
     if (alist == &global_alist && i == global_alist.al_ga.ga_len - 1) {
       arg_had_last = true;
     }
@@ -4894,6 +4896,10 @@ do_arg_all(
         }
       }
     } else if (split_ret == OK) {
+      // trigger events for tab drop
+      if (tab_drop_empty_window && i == count - 1) {
+        autocmd_no_enter--;
+      }
       if (!use_firstwin) {              // split current window
         p_ea_save = p_ea;
         p_ea = true;                    // use space from all windows
@@ -4919,6 +4925,9 @@ do_arg_all(
                       || bufIsChanged(curwin->w_buffer))
                      ? ECMD_HIDE : 0) + ECMD_OLDBUF,
                     curwin);
+      if (tab_drop_empty_window && i == count - 1) {
+        autocmd_no_enter++;
+      }
       if (use_firstwin) {
         autocmd_no_leave++;
       }

src/nvim/testdir/test_tabpage.vim

@@ -222,6 +222,34 @@ function Test_tabpage_with_autocmd()
   1tabonly!
 endfunction
 
+" Test autocommands on tab drop
+function Test_tabpage_with_autocmd_tab_drop()
+  augroup TestTabpageGroup
+    au!
+    autocmd TabEnter * call add(s:li, 'TabEnter')
+    autocmd WinEnter * call add(s:li, 'WinEnter')
+    autocmd BufEnter * call add(s:li, 'BufEnter')
+    autocmd TabLeave * call add(s:li, 'TabLeave')
+    autocmd WinLeave * call add(s:li, 'WinLeave')
+    autocmd BufLeave * call add(s:li, 'BufLeave')
+  augroup END
+
+  let s:li = []
+  tab drop test1
+  call assert_equal(['BufLeave', 'BufEnter'], s:li)
+
+  let s:li = []
+  tab drop test2 test3
+  call assert_equal([
+        \ 'TabLeave', 'TabEnter', 'TabLeave', 'TabEnter',
+        \ 'TabLeave', 'WinEnter', 'TabEnter', 'BufEnter',
+        \ 'TabLeave', 'WinEnter', 'TabEnter', 'BufEnter'], s:li)
+
+  autocmd! TestTabpageGroup
+  augroup! TestTabpageGroup
+  1tabonly!
+endfunction
+
 function Test_tabpage_with_tab_modifier()
   for n in range(4)
     tabedit