vim-patch:8.2.4160: cannot change the register used for Select mode delete

Problem:    Cannot change the register used for Select mode delete.
Solution:   Make CTRL-R set the register to be used when deleting text for
            Select mode. (Shougo Matsushita, closes vim/vim#9531)
https://github.com/vim/vim/commit/4ede01f18884961f2e008880b4964e5d61ea5c36

5 files changed, 91 insertions, 5 deletions

diff --git a/runtime/doc/visual.txt b/runtime/doc/visual.txt
index 4a69fc989b..5563a56216 100644
--- a/runtime/doc/visual.txt
+++ b/runtime/doc/visual.txt
@@ -478,6 +478,10 @@ Commands in Select mode:
 - ESC stops Select mode.
 - CTRL-O switches to Visual mode for the duration of one command. *v_CTRL-O*
 - CTRL-G switches to Visual mode.
+- CTRL-R {register} selects the register to be used for the text that is
+  deleted when typing text.					  *v_CTRL-R*
+  Unless you specify the "_" (black hole) register, the unnamed register is
+  also overwritten.
 
 Otherwise, typed characters are handled as in Visual mode.
 
diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index 40c61d01b5..e0ea4060fd 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -524,6 +524,8 @@ EXTERN pos_T VIsual;
 EXTERN int VIsual_active INIT(= false);
 /// Whether Select mode is active.
 EXTERN int VIsual_select INIT(= false);
+/// Register name for Select mode
+EXTERN int VIsual_select_reg INIT(= 0);
 /// Restart Select mode when next cmd finished
 EXTERN int restart_VIsual_select INIT(= 0);
 /// Whether to restart the selection after a Select-mode mapping or menu.
diff --git a/src/nvim/normal.c b/src/nvim/normal.c
index 2b5b47c0b3..2fce3e10b8 100644
--- a/src/nvim/normal.c
+++ b/src/nvim/normal.c
@@ -164,7 +164,7 @@ static const struct nv_cmd {
   { Ctrl_O,    nv_ctrlo,       0,                      0 },
   { Ctrl_P,    nv_up,          NV_STS,                 false },
   { Ctrl_Q,    nv_visual,      0,                      false },
-  { Ctrl_R,    nv_redo,        0,                      0 },
+  { Ctrl_R,    nv_redo_or_register, 0,                      0 },
   { Ctrl_S,    nv_ignore,      0,                      0 },
   { Ctrl_T,    nv_tagpop,      NV_NCW,                 0 },
   { Ctrl_U,    nv_halfpage,    0,                      0 },
@@ -961,6 +961,7 @@ normal_end:
       && s->oa.regname == 0) {
     if (restart_VIsual_select == 1) {
       VIsual_select = true;
+      VIsual_select_reg = 0;
       trigger_modechanged();
       showmode();
       restart_VIsual_select = 0;
@@ -6186,6 +6187,7 @@ static void nv_g_cmd(cmdarg_T *cap)
       // start Select mode.
       if (cap->arg) {
         VIsual_select = true;
+        VIsual_select_reg = 0;
       } else {
         may_start_select('c');
       }
@@ -6698,11 +6700,26 @@ static void nv_dot(cmdarg_T *cap)
   }
 }
 
-/*
- * CTRL-R: undo undo
- */
-static void nv_redo(cmdarg_T *cap)
+// CTRL-R: undo undo or specify register in select mode
+static void nv_redo_or_register(cmdarg_T *cap)
 {
+  if (VIsual_select && VIsual_active) {
+    int reg;
+    // Get register name
+    no_mapping++;
+    reg = plain_vgetc();
+    LANGMAP_ADJUST(reg, true);
+    no_mapping--;
+
+    if (reg == '"') {
+      // the unnamed register is 0
+      reg = 0;
+    }
+
+    VIsual_select_reg = valid_yank_reg(reg, true) ? reg : 0;
+    return;
+  }
+
   if (!checkclearopq(cap->oap)) {
     u_redo((int)cap->count1);
     curwin->w_set_curswant = true;
@@ -7023,6 +7040,7 @@ static void nv_select(cmdarg_T *cap)
 {
   if (VIsual_active) {
     VIsual_select = true;
+    VIsual_select_reg = 0;
   } else if (VIsual_reselect) {
     cap->nchar = 'v';               // fake "gv" command
     cap->arg = true;
diff --git a/src/nvim/ops.c b/src/nvim/ops.c
index 1a12cb636a..497d756cdd 100644
--- a/src/nvim/ops.c
+++ b/src/nvim/ops.c
@@ -1435,6 +1435,11 @@ int op_delete(oparg_T *oap)
     return FAIL;
   }
 
+  if (VIsual_select && oap->is_VIsual) {
+    // Use the register given with CTRL_R, defaults to zero
+    oap->regname = VIsual_select_reg;
+  }
+
   mb_adjust_opend(oap);
 
   /*
diff --git a/src/nvim/testdir/test_selectmode.vim b/src/nvim/testdir/test_selectmode.vim
new file mode 100644
index 0000000000..b483841060
--- /dev/null
+++ b/src/nvim/testdir/test_selectmode.vim
@@ -0,0 +1,57 @@
+" Test for Select-mode
+
+source shared.vim
+
+" Test for selecting a register with CTRL-R
+func Test_selectmode_register()
+  new
+
+  " Default behavior: use unnamed register
+  call setline(1, 'foo')
+  call setreg('"', 'bar')
+  call setreg('a', 'baz')
+  exe ":norm! v\<c-g>a"
+  call assert_equal(getline('.'), 'aoo')
+  call assert_equal('f', getreg('"'))
+  call assert_equal('baz', getreg('a'))
+
+  " Use the black hole register
+  call setline(1, 'foo')
+  call setreg('"', 'bar')
+  call setreg('a', 'baz')
+  exe ":norm! v\<c-g>\<c-r>_a"
+  call assert_equal(getline('.'), 'aoo')
+  call assert_equal('bar', getreg('"'))
+  call assert_equal('baz', getreg('a'))
+
+  " Invalid register: use unnamed register
+  call setline(1, 'foo')
+  call setreg('"', 'bar')
+  call setreg('a', 'baz')
+  exe ":norm! v\<c-g>\<c-r>?a"
+  call assert_equal(getline('.'), 'aoo')
+  call assert_equal('f', getreg('"'))
+  call assert_equal('baz', getreg('a'))
+
+  " Use unnamed register
+  call setline(1, 'foo')
+  call setreg('"', 'bar')
+  call setreg('a', 'baz')
+  exe ":norm! v\<c-g>\<c-r>\"a"
+  call assert_equal(getline('.'), 'aoo')
+  call assert_equal('f', getreg('"'))
+  call assert_equal('baz', getreg('a'))
+
+  " use specicifed register, unnamed register is also written
+  call setline(1, 'foo')
+  call setreg('"', 'bar')
+  call setreg('a', 'baz')
+  exe ":norm! v\<c-g>\<c-r>aa"
+  call assert_equal(getline('.'), 'aoo')
+  call assert_equal('f', getreg('"'))
+  call assert_equal('f', getreg('a'))
+
+  bw!
+endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab