vim-patch:8.2.0839: dropping modifier when putting a character back in typeahead

Problem:    Dropping modifier when putting a character back in typeahead.
Solution:   Add modifier to ins_char_typebuf(). (closes vim/vim#6158)
https://github.com/vim/vim/commit/b42c0d54279b1fdb79652db0c84171e213458809

Vim's test doesn't seem to work properly as the hit-enter prompt seems
to be delayed. Add a Lua screen test.

7 files changed, 53 insertions, 3 deletions

diff --git a/src/nvim/getchar.c b/src/nvim/getchar.c
index f92aa14c78..fbe503bcd4 100644
--- a/src/nvim/getchar.c
+++ b/src/nvim/getchar.c
@@ -1499,6 +1499,8 @@ int vgetc(void)
     static size_t last_vgetc_recorded_len = 0;
 
     mod_mask = 0;
+    vgetc_mod_mask = 0;
+    vgetc_char = 0;
 
     // last_recorded_len can be larger than last_vgetc_recorded_len
     // if peeking records more
@@ -1624,6 +1626,10 @@ int vgetc(void)
 
       // A modifier was not used for a mapping, apply it to ASCII
       // keys.  Shift would already have been applied.
+      // Remember the character and mod_mask from before, in some
+      // cases they are put back in the typeahead buffer.
+      vgetc_mod_mask = mod_mask;
+      vgetc_char = c;
       c = merge_modifiers(c);
 
       // If mappings are enabled (i.e., not Ctrl-v) and the user directly typed
diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index e07a0e22ca..6e0b445656 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -129,6 +129,9 @@ typedef off_t off_T;
 // held down based on the MOD_MASK_* symbols that are read first.
 EXTERN int mod_mask INIT(= 0);  // current key modifiers
 
+// The value of "mod_mask" and the unmodified character before calling merge_modifiers().
+EXTERN int vgetc_mod_mask INIT(= 0);
+EXTERN int vgetc_char INIT(= 0);
 
 // Cmdline_row is the row where the command line starts, just below the
 // last window.
diff --git a/src/nvim/message.c b/src/nvim/message.c
index 6708001495..90af920396 100644
--- a/src/nvim/message.c
+++ b/src/nvim/message.c
@@ -1214,7 +1214,7 @@ void wait_return(int redraw)
     } else if (vim_strchr((char_u *)"\r\n ", c) == NULL && c != Ctrl_C) {
       // Put the character back in the typeahead buffer.  Don't use the
       // stuff buffer, because lmaps wouldn't work.
-      ins_char_typebuf(c, mod_mask);
+      ins_char_typebuf(vgetc_char, vgetc_mod_mask);
       do_redraw = true;             // need a redraw even though there is
                                     // typeahead
     }
diff --git a/src/nvim/normal.c b/src/nvim/normal.c
index 73ea995d8f..a04316f5e4 100644
--- a/src/nvim/normal.c
+++ b/src/nvim/normal.c
@@ -995,7 +995,7 @@ static int normal_execute(VimState *state, int key)
     // restart automatically.
     // Insert the typed character in the typeahead buffer, so that it can
     // be mapped in Insert mode.  Required for ":lmap" to work.
-    int len = ins_char_typebuf(s->c, mod_mask);
+    int len = ins_char_typebuf(vgetc_char, vgetc_mod_mask);
 
     // When recording and gotchars() was called the character will be
     // recorded again, remove the previous recording.
diff --git a/src/nvim/terminal.c b/src/nvim/terminal.c
index fd870361c7..5f536c0b7a 100644
--- a/src/nvim/terminal.c
+++ b/src/nvim/terminal.c
@@ -1348,7 +1348,7 @@ static bool send_mouse_event(Terminal *term, int c)
   }
 
 end:
-  ins_char_typebuf(c, mod_mask);
+  ins_char_typebuf(vgetc_char, vgetc_mod_mask);
   return true;
 }
 
diff --git a/src/nvim/testdir/test_messages.vim b/src/nvim/testdir/test_messages.vim
index 82c4cc128b..2e9b0a8531 100644
--- a/src/nvim/testdir/test_messages.vim
+++ b/src/nvim/testdir/test_messages.vim
@@ -112,6 +112,14 @@ func Test_echospace()
   set ruler& showcmd&
 endfunc
 
+func Test_mapping_at_hit_return_prompt()
+  nnoremap <C-B> :echo "hit ctrl-b"<CR>
+  call feedkeys(":ls\<CR>", "xt")
+  call feedkeys("\<C-B>", "xt")
+  call assert_match('hit ctrl-b', Screenline(&lines - 1))
+  nunmap <C-B>
+endfunc
+
 func Test_quit_long_message()
   CheckScreendump
 
diff --git a/test/functional/ui/input_spec.lua b/test/functional/ui/input_spec.lua
index 8925dda730..799aad8d55 100644
--- a/test/functional/ui/input_spec.lua
+++ b/test/functional/ui/input_spec.lua
@@ -216,6 +216,39 @@ it('Ctrl-6 is Ctrl-^ vim-patch:8.1.2333', function()
   eq('aaa', funcs.bufname())
 end)
 
+it('typing a simplifiable key at hit-enter prompt triggers mapping vim-patch:8.2.0839', function()
+  local screen = Screen.new(60,8)
+  screen:set_default_attr_ids({
+    [1] = {bold = true, foreground = Screen.colors.Blue},  -- NonText
+    [2] = {bold = true, reverse = true},  -- MsgSeparator
+    [3] = {bold = true, foreground = Screen.colors.SeaGreen},  -- MoreMsg
+  })
+  screen:attach()
+  command([[nnoremap <C-6> <Cmd>echo 'hit ctrl-6'<CR>]])
+  feed_command('ls')
+  screen:expect([[
+                                                                |
+    {1:~                                                           }|
+    {1:~                                                           }|
+    {1:~                                                           }|
+    {2:                                                            }|
+    :ls                                                         |
+      1 %a   "[No Name]"                    line 1              |
+    {3:Press ENTER or type command to continue}^                     |
+  ]])
+  feed('<C-6>')
+  screen:expect([[
+    ^                                                            |
+    {1:~                                                           }|
+    {1:~                                                           }|
+    {1:~                                                           }|
+    {1:~                                                           }|
+    {1:~                                                           }|
+    {1:~                                                           }|
+    hit ctrl-6                                                  |
+  ]])
+end)
+
 describe('input non-printable chars', function()
   after_each(function()
     os.remove('Xtest-overwrite')