vim-patch:8.2.4028: ml_get error with :doautoall and Visual area

Problem:    ml_get error with :doautoall and Visual area. (Sean Dewar)
Solution:   Disable Visual mode while executing autocommands.
cb1956d6f2

This should also fix #16937 for nvim_buf_call, so test for it.

src/nvim/autocmd.c

@@ -1069,8 +1069,6 @@ void ex_doautoall(exarg_T *eap)
       do_modelines(0);
     }
   }
-
-  check_cursor();  // just in case lines got deleted
 }
 
 /// Check *argp for <nomodeline>.  When it is present return false, otherwise
@@ -1171,6 +1169,10 @@ void aucmd_prepbuf(aco_save_T *aco, buf_T *buf)
   curbuf = buf;
   aco->new_curwin_handle = curwin->handle;
   set_bufref(&aco->new_curbuf, curbuf);
+
+  // disable the Visual area, the position may be invalid in another buffer
+  aco->save_VIsual_active = VIsual_active;
+  VIsual_active = false;
 }
 
 /// Cleanup after executing autocommands for a (hidden) buffer.
@@ -1267,6 +1269,12 @@ win_found:
       check_cursor();
     }
   }
+
+  check_cursor();  // just in case lines got deleted
+  VIsual_active = aco->save_VIsual_active;
+  if (VIsual_active) {
+    check_pos(curbuf, &VIsual);
+  }
 }
 
 /// Execute autocommands for "event" and file name "fname".

src/nvim/autocmd.h

@@ -14,6 +14,7 @@ typedef struct {
   handle_T save_prevwin_handle;   ///< ID of saved prevwin
   bufref_T new_curbuf;            ///< new curbuf
   char_u *globaldir;              ///< saved value of globaldir
+  bool save_VIsual_active;        ///< saved VIsual_active
 } aco_save_T;
 
 typedef struct AutoCmd {

src/nvim/testdir/test_autocmd.vim

@@ -2543,6 +2543,16 @@ func Test_close_autocmd_tab()
   %bwipe!
 endfunc
 
+func Test_Visual_doautoall_redraw()
+  call setline(1, ['a', 'b'])
+  new
+  wincmd p
+  call feedkeys("G\<C-V>", 'txn')
+  autocmd User Explode ++once redraw
+  doautoall User Explode
+  %bwipe!
+endfunc
+
 func Test_autocmd_closes_window()
   au BufNew,BufWinLeave * e %e
   file yyy

test/functional/lua/vim_spec.lua

@@ -2406,6 +2406,17 @@ describe('lua stdlib', function()
       eq(buf1, meths.get_current_buf())
       eq(buf2, val)
     end)
+
+    it('does not cause ml_get errors with invalid visual selection', function()
+      -- Should be fixed by vim-patch:8.2.4028.
+      exec_lua [[
+        local a = vim.api
+        local t = function(s) return a.nvim_replace_termcodes(s, true, true, true) end
+        a.nvim_buf_set_lines(0, 0, -1, true, {"a", "b", "c"})
+        a.nvim_feedkeys(t "G<C-V>", "txn", false)
+        a.nvim_buf_call(a.nvim_create_buf(false, true), function() vim.cmd "redraw" end)
+      ]]
+    end)
   end)
 
   describe('vim.api.nvim_win_call', function()