fix(messages): avoid empty msg_showmode with 'noshowmode'

src/nvim/message.c

@@ -3183,7 +3183,11 @@ void msg_ext_flush_showmode(void)
 {
   // Showmode messages doesn't interrupt normal message flow, so we use
   // separate event. Still reuse the same chunking logic, for simplicity.
-  if (ui_has(kUIMessages)) {
+  // This is called unconditionally; check if we are emitting, or have
+  // emitted non-empty "content".
+  static bool clear = false;
+  if (ui_has(kUIMessages) && (msg_ext_last_attr != -1 || clear)) {
+    clear = msg_ext_last_attr != -1;
     msg_ext_emit_chunk();
     Array *tofree = msg_ext_init_chunks();
     ui_call_msg_showmode(*tofree);

test/functional/lua/ui_event_spec.lua

@@ -345,31 +345,36 @@ describe('vim.ui_attach', function()
         vim.api.nvim_buf_set_lines(0, -2, -1, false, { err[1] })
       end)
     ]])
+    local s1 = [[
+      ^                                        |
+      {1:~                                       }|*4
+    ]]
+    screen:expect(s1)
+    feed('QQQQQQ<CR>')
     screen:expect({
       grid = [[
-        ^                                        |
+        {9:obal 'err' (a nil value)}                |
-        {1:~                                       }|*4
+        {9:stack traceback:}                        |
-      ]],
+        {9:        [string "<nvim>"]:2: in function}|
-    })
+        {9: <[string "<nvim>"]:1>}                  |
-    feed('ifoo')
-    screen:expect({
-      grid = [[
-        foo^                                     |
-        {1:~                                       }|*4
-      ]],
-      showmode = { { '-- INSERT --', 5, 11 } },
-    })
-    feed('<esc>:1mes clear<cr>:mes<cr>')
-    screen:expect({
-      grid = [[
-        foo                                     |
-        {3:                                        }|
-        {9:Excessive errors in vim.ui_attach() call}|
-        {9:back from ns: 1.}                        |
         {100:Press ENTER or type command to continue}^ |
       ]],
-      cmdline = { { abort = false } },
+      messages = {
+        {
+          content = { { 'Press ENTER or type command to continue', 100, 18 } },
+          history = true,
+          kind = 'return_prompt',
+        },
+      },
     })
+    feed(':1mes clear<CR>:mes<CR>')
+    screen:expect([[
+                                              |
+      {3:                                        }|
+      {9:Excessive errors in vim.ui_attach() call}|
+      {9:back from ns: 1.}                        |
+      {100:Press ENTER or type command to continue}^ |
+    ]])
     feed('<cr>')
     -- Also when scheduled
     exec_lua([[
@@ -378,7 +383,7 @@ describe('vim.ui_attach', function()
       end)
     ]])
     screen:expect({
-      any = 'fo^o',
+      grid = s1,
       messages = {
         {
           content = {
@@ -410,14 +415,12 @@ describe('vim.ui_attach', function()
       },
     })
     feed('<esc>:1mes clear<cr>:mes<cr>')
-    screen:expect({
+    screen:expect([[
-      grid = [[
+                                              |
-        foo                                     |
+      {3:                                        }|
-        {3:                                        }|
+      {9:Excessive errors in vim.ui_attach() call}|
-        {9:Excessive errors in vim.ui_attach() call}|
+      {9:back from ns: 2.}                        |
-        {9:back from ns: 2.}                        |
+      {100:Press ENTER or type command to continue}^ |
-        {100:Press ENTER or type command to continue}^ |
+    ]])
-      ]],
-    })
   end)
 end)

test/functional/ui/messages_spec.lua

@@ -1391,13 +1391,25 @@ stack traceback:
       screen_showmode(...)
       showmode = showmode + 1
     end
+    local s1 = [[
+      ^                         |
+      {1:~                        }|*4
+    ]]
+    screen:expect(s1)
+    eq(showmode, 0)
+    feed('i')
     screen:expect({
-      grid = [[
+      grid = s1,
-        ^                         |
+      showmode = { { '-- INSERT --', 5, 11 } },
-        {1:~                        }|*4
-      ]],
     })
-    eq(showmode, 1)
+    eq(showmode, 2)
+    command('set noshowmode')
+    feed('<Esc>')
+    screen:expect(s1)
+    eq(showmode, 3)
+    feed('i')
+    screen:expect_unchanged()
+    eq(showmode, 3)
   end)
 
   it('emits single message for multiline print())', function()