patch 8.0.1160: getting tab-local variable fails after closing window

Problem:    Getting tab-local variable fails after closing window.
Solution:   set tp_firstwin and tp_lastwin. (Jason Franklin, closes #2170)

Author: brammool

src/evalfunc.c

@@ -5183,8 +5183,8 @@ f_gettabvar(typval_T *argvars, typval_T *rettv)
 	/* Set tp to be our tabpage, temporarily.  Also set the window to the
 	 * first window in the tabpage, otherwise the window is not valid. */
 	if (switch_win(&oldcurwin, &oldtabpage,
-		    tp->tp_firstwin == NULL ? firstwin : tp->tp_firstwin, tp, TRUE)
-									== OK)
+		tp == curtab || tp->tp_firstwin == NULL ? firstwin
+					    : tp->tp_firstwin, tp, TRUE) == OK)
 	{
 	    /* look up the variable */
 	    /* Let gettabvar({nr}, "") return the "t:" dictionary. */

src/testdir/test_getvar.vim

@@ -86,3 +86,19 @@ func Test_var()
   call assert_equal(1, gettabwinvar(2, 3, '&nux', 1))
   tabonly
 endfunc
+
+" It was discovered that "gettabvar()" would fail if called from within the
+" tabline when the user closed a window.  This test confirms the fix.
+func Test_gettabvar_in_tabline()
+  let t:var_str = 'value'
+
+  set tabline=%{assert_equal('value',gettabvar(1,'var_str'))}
+  set showtabline=2
+
+  " Simulate the user opening a split (which becomes window #1) and then
+  " closing the split, which triggers the redrawing of the tabline.
+  leftabove split
+  redrawstatus!
+  close
+  redrawstatus!
+endfunc

src/version.c

@@ -761,6 +761,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1160,
 /**/
     1159,
 /**/

src/window.c

@@ -4775,13 +4775,14 @@ win_remove(
     if (wp->w_prev != NULL)
 	wp->w_prev->w_next = wp->w_next;
     else if (tp == NULL)
-	firstwin = wp->w_next;
+	firstwin = curtab->tp_firstwin = wp->w_next;
     else
 	tp->tp_firstwin = wp->w_next;
+
     if (wp->w_next != NULL)
 	wp->w_next->w_prev = wp->w_prev;
     else if (tp == NULL)
-	lastwin = wp->w_prev;
+	lastwin = curtab->tp_lastwin = wp->w_prev;
     else
 	tp->tp_lastwin = wp->w_prev;
 }
@@ -6597,11 +6598,11 @@ restore_snapshot_rec(frame_T *sn, frame_T *fr)
  */
     int
 switch_win(
-    win_T	**save_curwin UNUSED,
-    tabpage_T	**save_curtab UNUSED,
-    win_T	*win UNUSED,
-    tabpage_T	*tp UNUSED,
-    int		no_display UNUSED)
+    win_T	**save_curwin,
+    tabpage_T	**save_curtab,
+    win_T	*win,
+    tabpage_T	*tp,
+    int		no_display)
 {
 # ifdef FEAT_AUTOCMD
     block_autocmds();