patch 8.2.1636: get stuck if a popup filter causes an error

Problem:    Get stuck if a popup filter causes an error.
Solution:   Check whether the function can be called and does not cause an
            error.  (closes #6902)

src/popupwin.c

@@ -3126,6 +3126,7 @@ invoke_popup_filter(win_T *wp, int c)
     typval_T	argv[3];
     char_u	buf[NUMBUFLEN];
     linenr_T	old_lnum = wp->w_cursor.lnum;
+    int		prev_called_emsg = called_emsg;
 
     // Emergency exit: CTRL-C closes the popup.
     if (c == Ctrl_C)
@@ -3151,10 +3152,35 @@ invoke_popup_filter(win_T *wp, int c)
     argv[2].v_type = VAR_UNKNOWN;
 
     // NOTE: The callback might close the popup and make "wp" invalid.
-    call_callback(&wp->w_filter_cb, -1, &rettv, 2, argv);
+    if (call_callback(&wp->w_filter_cb, -1, &rettv, 2, argv) == FAIL)
+    {
+	// Cannot call the function, close the popup to avoid that the filter
+	// eats keys and the user can't get out.
+	popup_close_with_retval(wp, -1);
+	return 1;
+    }
+
     if (win_valid_popup(wp) && old_lnum != wp->w_cursor.lnum)
 	popup_highlight_curline(wp);
+
+    // If an error was given always return FALSE, so that keys are not
+    // consumed and the user can type something.
+    // If we get three errors in a row then close the popup.  Decrement the
+    // error count by 1/10 if there are no errors, thus allowing up to 1 in
+    // 10 calls to cause an error.
+    if (win_valid_popup(wp) && called_emsg > prev_called_emsg)
+    {
+	wp->w_filter_errors += 10;
+	if (wp->w_filter_errors >= 30)
+	    popup_close_with_retval(wp, -1);
+	res = FALSE;
+    }
+    else
+    {
+	if (win_valid_popup(wp) && wp->w_filter_errors > 0)
+	    --wp->w_filter_errors;
 	res = tv_get_bool(&rettv);
+    }
 
     vim_free(argv[1].vval.v_string);
     clear_tv(&rettv);

src/structs.h

@@ -3338,6 +3338,7 @@ struct window_S
 				      // with "cursorline" set
     callback_T	w_close_cb;	    // popup close callback
     callback_T	w_filter_cb;	    // popup filter callback
+    int		w_filter_errors;    // popup filter error count
     int		w_filter_mode;	    // mode when filter callback is used
 
     win_T	*w_popup_curwin;    // close popup if curwin differs

src/testdir/dumps/Test_popupwin_three_errors_1.dump

@@ -0,0 +1,10 @@
+> +0&#ffffff0@74
+|~+0#4040ff13&| @73
+|~| @73
+|~| @73
+|~| @27|o+0#0000001#ffd7ff255|n|e| |t|w|o| |t|h|r|e@1|.@2| +0#4040ff13#ffffff0@29
+|~| @73
+|~| @73
+|~| @73
+|E+0#ffffff16#e000002|8|9|6|:| |A|r|g|u|m|e|n|t| |o|f| |f|i|l|t|e|r|(|)| |m|u|s|t| |b|e| |a| |L|i|s|t|,| |D|i|c|t|i|o|n|a|r|y| |o|r| |B|l|o|b| +0#0000000#ffffff0@13
+@57|0|,|0|-|1| @8|A|l@1| 

src/testdir/dumps/Test_popupwin_three_errors_2.dump

@@ -0,0 +1,10 @@
+> +0&#ffffff0@74
+|~+0#4040ff13&| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|E+0#ffffff16#e000002|8|9|6|:| |A|r|g|u|m|e|n|t| |o|f| |f|i|l|t|e|r|(|)| |m|u|s|t| |b|e| |a| |L|i|s|t|,| |D|i|c|t|i|o|n|a|r|y| |o|r| |B|l|o|b| +0#0000000#ffffff0@13
+@57|0|,|0|-|1| @8|A|l@1| 

src/testdir/dumps/Test_popupwin_wrong_name.dump

@@ -0,0 +1,10 @@
+> +0&#ffffff0@74
+|~+0#4040ff13&| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|~| @73
+|E+0#ffffff16#e000002|1@1|7|:| |U|n|k|n|o|w|n| |f|u|n|c|t|i|o|n|:| |N|o|S|u|c|h|F|u|n|c| +0#0000000#ffffff0@22|0|,|0|-|1| @8|A|l@1| 

src/testdir/test_popupwin.vim

@@ -3516,7 +3516,44 @@ func Test_popupwin_filter_close_ctrl_c()
   call VerifyScreenDump(buf, 'Test_popupwin_ctrl_c', {})
 
   call StopVimInTerminal(buf)
-  call delete('XtestPopupCorners')
+  call delete('XtestPopupCtrlC')
+endfunc
+
+func Test_popupwin_filter_close_wrong_name()
+  CheckScreendump
+
+  let lines =<< trim END
+      call popup_create('one two three...', {'filter': 'NoSuchFunc'})
+  END
+  call writefile(lines, 'XtestPopupWrongName')
+
+  let buf = RunVimInTerminal('-S XtestPopupWrongName', #{rows: 10})
+
+  call term_sendkeys(buf, "j")
+  call VerifyScreenDump(buf, 'Test_popupwin_wrong_name', {})
+
+  call StopVimInTerminal(buf)
+  call delete('XtestPopupWrongName')
+endfunc
+
+func Test_popupwin_filter_close_three_errors()
+  CheckScreendump
+
+  let lines =<< trim END
+      set cmdheight=2
+      call popup_create('one two three...', {'filter': 'filter'})
+  END
+  call writefile(lines, 'XtestPopupThreeErrors')
+
+  let buf = RunVimInTerminal('-S XtestPopupThreeErrors', #{rows: 10})
+
+  call term_sendkeys(buf, "jj")
+  call VerifyScreenDump(buf, 'Test_popupwin_three_errors_1', {})
+  call term_sendkeys(buf, "j")
+  call VerifyScreenDump(buf, 'Test_popupwin_three_errors_2', {})
+
+  call StopVimInTerminal(buf)
+  call delete('XtestPopupThreeErrors')
 endfunc
 
 func Test_popupwin_atcursor_far_right()

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1636,
 /**/
     1635,
 /**/