patch 9.0.0078: star register is unexpectedly changed when deleting

Problem:    Star register is changed when deleting and both "unnamed" and
            "unnamedplus" are in 'clipboard'.
Solution:   Make the use of the star register work as documented. (Ernie Rael,
            closes #10669)

src/register.c

@@ -1409,7 +1409,8 @@ op_yank(oparg_T *oap, int deleting, int mess)
 # ifdef FEAT_X11
     // If we were yanking to the '+' register, send result to selection.
     // Also copy to the '*' register, in case auto-select is off.  But not when
-    // 'clipboard' has "unnamedplus" and not "unnamed".
+    // 'clipboard' has "unnamedplus" and not "unnamed"; and not when
+    // deleting and both "unnamedplus" and "unnamed".
     if (clip_plus.available
 	    && (curr == &(y_regs[PLUS_REGISTER])
 		|| (!deleting && oap->regname == 0
@@ -1425,6 +1426,8 @@ op_yank(oparg_T *oap, int deleting, int mess)
 	if (!clip_isautosel_star()
 		&& !clip_isautosel_plus()
 		&& !((clip_unnamed | clip_unnamed_saved) == CLIP_UNNAMED_PLUS)
+		&& !(deleting && (clip_unnamed | clip_unnamed_saved)
+					 == (CLIP_UNNAMED | CLIP_UNNAMED_PLUS))
 		&& !did_star
 		&& curr == &(y_regs[PLUS_REGISTER]))
 	{

src/testdir/check.vim

@@ -233,6 +233,15 @@ func CheckX11BasedGui()
   endif
 endfunc
 
+" Command to check that there are two clipboards
+command CheckTwoClipboards call CheckTwoClipboards()
+func CheckTwoClipboards()
+  " avoid changing the clipboard here, only X11 supports both
+  if !has('X11')
+    throw 'Skipped: requires two clipboards'
+  endif
+endfunc
+
 " Command to check for satisfying any of the conditions.
 " e.g. CheckAnyOf Feature:bsd Feature:sun Linux
 command -nargs=+ CheckAnyOf call CheckAnyOf(<f-args>)

src/testdir/test_registers.vim

@@ -411,6 +411,36 @@ func Test_clipboard_regs()
   bwipe!
 endfunc
 
+" Test unnamed for both clipboard registers (* and +)
+func Test_clipboard_regs_both_unnamed()
+  CheckNotGui
+  CheckFeature clipboard_working
+  CheckTwoClipboards
+
+  let @* = 'xxx'
+  let @+ = 'xxx'
+
+  new
+
+  set clipboard=unnamed,unnamedplus
+  call setline(1, ['foo', 'bar'])
+
+  " op_yank copies to both
+  :1
+  :normal yw
+  call assert_equal('foo', getreg('*'))
+  call assert_equal('foo', getreg('+'))
+
+  " op_delete only copies to '+'
+  :2
+  :normal dw
+  call assert_equal('foo', getreg('*'))
+  call assert_equal('bar', getreg('+'))
+
+  set clipboard&vim
+  bwipe!
+endfunc
+
 " Test for restarting the current mode (insert or virtual replace) after
 " executing the contents of a register
 func Test_put_reg_restart_mode()

src/version.c

@@ -735,6 +735,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    78,
 /**/
     77,
 /**/