vim-patch:8.2.2427: can still switch windows for 'completefunc'

Problem:    Can still switch windows for 'completefunc'.
Solution:   Also disallow switching windows for other completions.
3eb6bd9c2b

Assert E565 instead of E578.
Need to assert a different string because patch 8.2.1919 hasn't been
ported yet.

src/nvim/edit.c

@@ -136,7 +136,6 @@ static char *ctrl_x_mode_names[] = {
 };
 
 static char e_hitend[] = N_("Hit end of paragraph");
-static char e_complwin[] = N_("E839: Completion function changed window");
 static char e_compldel[] = N_("E840: Completion function deleted text");
 
 /*
@@ -3939,8 +3938,6 @@ static void expand_by_function(int type, char_u *base)
   dict_T *matchdict = NULL;
   char_u *funcname;
   pos_T pos;
-  win_T *curwin_save;
-  buf_T *curbuf_save;
   typval_T rettv;
   const int save_State = State;
 
@@ -3959,8 +3956,6 @@ static void expand_by_function(int type, char_u *base)
   args[1].vval.v_string = base != NULL ? (char *)base : "";
 
   pos = curwin->w_cursor;
-  curwin_save = curwin;
-  curbuf_save = curbuf;
   // Lock the text to avoid weird things from happening.  Also disallow
   // switching to another window, it should not be needed and may end up in
   // Insert mode in another buffer.
@@ -3985,10 +3980,6 @@ static void expand_by_function(int type, char_u *base)
   }
   textlock--;
 
-  if (curwin_save != curwin || curbuf_save != curbuf) {
-    emsg(_(e_complwin));
-    goto theend;
-  }
   curwin->w_cursor = pos;       // restore the cursor position
   validate_cursor();
   if (!equalpos(curwin->w_cursor, pos)) {
@@ -5226,8 +5217,6 @@ static int ins_complete(int c, bool enable_pum)
       // set to 1 to obtain the length of text to use for completion.
       char_u *funcname;
       pos_T pos;
-      win_T *curwin_save;
-      buf_T *curbuf_save;
       const int save_State = State;
 
       // Call 'completefunc' or 'omnifunc' and get pattern length as a string
@@ -5248,15 +5237,11 @@ static int ins_complete(int c, bool enable_pum)
       args[1].vval.v_string = "";
 
       pos = curwin->w_cursor;
-      curwin_save = curwin;
+      textlock++;
-      curbuf_save = curbuf;
       colnr_T col = (colnr_T)call_func_retnr((char *)funcname, 2, args);
+      textlock--;
 
       State = save_State;
-      if (curwin_save != curwin || curbuf_save != curbuf) {
-        emsg(_(e_complwin));
-        return FAIL;
-      }
       curwin->w_cursor = pos;           // restore the cursor position
       validate_cursor();
       if (!equalpos(curwin->w_cursor, pos)) {

src/nvim/testdir/test_ins_complete.vim

@@ -614,7 +614,7 @@ func Test_completefunc_error()
   endfunc
   set completefunc=CompleteFunc
   call setline(1, ['', 'abcd', ''])
-  call assert_fails('exe "normal 2G$a\<C-X>\<C-U>"', 'E840:')
+  call assert_fails('exe "normal 2G$a\<C-X>\<C-U>"', 'E565:')
 
   " delete text when called for the second time
   func CompleteFunc2(findstart, base)

src/nvim/testdir/test_popup.vim

@@ -382,11 +382,11 @@ func Test_completefunc_opens_new_window_two()
   setlocal completefunc=DummyCompleteTwo
   call setline(1, 'two')
   /^two
-  call assert_fails('call feedkeys("A\<C-X>\<C-U>\<C-N>\<Esc>", "x")', 'E764:')
+  call assert_fails('call feedkeys("A\<C-X>\<C-U>\<C-N>\<Esc>", "x")', 'E565:')
-  call assert_notequal(winid, win_getid())
-  q!
   call assert_equal(winid, win_getid())
-  call assert_equal('two', getline(1))
+  " v8.2.1919 hasn't been ported yet
+  " call assert_equal('twodef', getline(1))
+  call assert_equal('twoDEF', getline(1))
   q!
 endfunc