[RDY] Fix wildmode=list,full and display+=msgsep interaction (#10103)

* Fix wildmode=list and display+=msgsep interaction
* Add test to check ext_messages behaviour is unchanged

src/nvim/message.c

@@ -2053,7 +2053,7 @@ int msg_scrollsize(void)
 /*
  * Scroll the screen up one line for displaying the next message line.
  */
-static void msg_scroll_up(void)
+void msg_scroll_up(void)
 {
   if (!msg_did_scroll) {
     ui_call_win_scroll_over_start();

src/nvim/screen.c

@@ -4765,12 +4765,12 @@ win_redr_status_matches (
 
   row = cmdline_row - 1;
   if (row >= 0) {
-    if (wild_menu_showing == 0) {
+    if (wild_menu_showing == 0 || wild_menu_showing == WM_LIST) {
       if (msg_scrolled > 0) {
         /* Put the wildmenu just above the command line.  If there is
          * no room, scroll the screen one line up. */
         if (cmdline_row == Rows - 1) {
-          grid_del_lines(&default_grid, 0, 1, (int)Rows, 0, (int)Columns);
+          msg_scroll_up();
           msg_scrolled++;
         } else {
           cmdline_row++;

test/functional/ui/messages_spec.lua

@@ -681,6 +681,43 @@ describe('ui/ext_messages', function()
   end)
 end)
 
+describe('ui/ext_messages', function()
+  local screen
+  before_each(function()
+    clear()
+    screen = Screen.new(25, 7)
+    screen:attach({rgb=true, ext_messages=true})
+    screen:set_default_attr_ids({
+      [1] = {bold = true, foreground = Screen.colors.Blue1},
+      [2] = {foreground = Screen.colors.Grey100, background = Screen.colors.Red},
+      [3] = {bold = true, reverse = true},
+      [4] = {bold = true, foreground = Screen.colors.SeaGreen4},
+    })
+  end)
+
+  it('wildmode=list', function()
+    command('set wildmenu wildmode=list')
+    feed(':set wildm<tab>')
+    screen:expect{grid=[[
+      ^                         |
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+      {1:~                        }|
+    ]], messages={{
+        content = {{'wildmenu  wildmode'}},
+        kind = '',
+     }},
+    cmdline={{
+      firstc = ':',
+      content = {{ 'set wildm' }},
+      pos = 9,
+    }}}
+  end)
+end)
+
 describe('ui/builtin messages', function()
   local screen
   before_each(function()

test/functional/ui/wildmode_spec.lua

@@ -169,6 +169,91 @@ describe("'wildmenu'", function()
   end)
 end)
 
+describe("'wildmenu'", function()
+  local screen
+  before_each(function()
+    clear()
+    -- screen needs to be more than 5 rows
+    -- otherwise the tabline is covered and will be redrawn
+    screen = Screen.new(25, 7)
+    screen:attach()
+  end)
+  after_each(function()
+    screen:detach()
+  end)
+
+  it('wildmode=list,full and display+=msgsep interact correctly #10092', function()
+    command('set display+=msgsep')
+    command('set wildmenu wildmode=list,full')
+    command('set showtabline=2')
+    feed(':set wildm<tab>')
+    screen:expect([[
+       [No Name]               |
+                               |
+      ~                        |
+                               |
+      :set wildm               |
+      wildmenu  wildmode       |
+      :set wildm^               |
+    ]])
+    feed('<tab>') -- trigger wildmode full
+    screen:expect([[
+       [No Name]               |
+                               |
+                               |
+      :set wildm               |
+      wildmenu  wildmode       |
+      wildmenu  wildmode       |
+      :set wildmenu^            |
+    ]])
+    feed('<Esc>')
+    screen:expect([[
+       [No Name]               |
+      ^                         |
+      ~                        |
+      ~                        |
+      ~                        |
+      ~                        |
+                               |
+    ]])
+  end)
+
+  it('wildmode=list,full and display-=msgsep interact correctly', function()
+    command('set display-=msgsep')
+    command('set wildmenu wildmode=list,full')
+    feed(':set wildm<tab>')
+    screen:expect([[
+      ~                        |
+      ~                        |
+      ~                        |
+      ~                        |
+      :set wildm               |
+      wildmenu  wildmode       |
+      :set wildm^               |
+    ]])
+    feed('<tab>') -- trigger wildmode full
+    screen:expect([[
+      ~                        |
+      ~                        |
+      ~                        |
+      :set wildm               |
+      wildmenu  wildmode       |
+      wildmenu  wildmode       |
+      :set wildmenu^            |
+    ]])
+    feed('<Esc>')
+    screen:expect([[
+      ^                         |
+      ~                        |
+      ~                        |
+      ~                        |
+      ~                        |
+      ~                        |
+                               |
+    ]])
+  end)
+end)
+
 describe('command line completion', function()
   local screen
   before_each(function()