fix(messages): :map output with ext_messages (#26126)

src/nvim/mapping.c

@@ -45,6 +45,7 @@
 #include "nvim/search.h"
 #include "nvim/strings.h"
 #include "nvim/types.h"
+#include "nvim/ui.h"
 #include "nvim/vim.h"
 
 /// List used for abbreviations.
@@ -220,7 +221,8 @@ static void showmap(mapblock_T *mp, bool local)
     return;
   }
 
-  if (msg_didout || msg_silent != 0) {
+  // When ext_messages is active, msg_didout is never set.
+  if (msg_didout || msg_silent != 0 || ui_has(kUIMessages)) {
     msg_putchar('\n');
     if (got_int) {          // 'q' typed at MORE prompt
       return;

test/functional/ui/messages_spec.lua

@@ -834,6 +834,19 @@ stack traceback:
     end}
   end)
 
+  it('supports multiline messages for :map', function()
+    command('mapclear')
+    command('nmap Y y$')
+    command('nmap Q @@')
+    command('nnoremap j k')
+    feed(':map<cr>')
+
+    screen:expect{messages={{
+      content = {{ "\nn  Q             @@\nn  Y             y$\nn  j           " }, { "*", 5 }, { " k" }},
+      kind = ''
+    }}}
+  end)
+
   it('wildmode=list', function()
     screen:try_resize(25, 7)
     screen:set_option('ext_popupmenu', false)