ext_cmdline: Added cmdline prompt

runtime/doc/msgpack_rpc.txt

@@ -462,6 +462,9 @@ states might be represented as separate modes.
         The first character of the command, which could be : / ? etc. With
 	the firstc, you know wheither it's a command or a search.
 
+["cmdline_prompt", prompt]
+        The prompt of the cmdline.
+
 ["cmdline", content, pos]
 	When cmdline_external is set to true, nvim will not draw the cmdline
 	on the grad, instead nvim will send ui events of the cmdline content

src/nvim/eval.c

@@ -11149,15 +11149,19 @@ void get_user_input(const typval_T *const argvars,
   // Only the part of the message after the last NL is considered as
   // prompt for the command line.
   const char *p = strrchr(prompt, '\n');
-  if (p == NULL) {
+  if (ui_is_external(kUICmdline)) {
     p = prompt;
   } else {
-    p++;
-    msg_start();
-    msg_clr_eos();
-    msg_puts_attr_len(prompt, p - prompt, echo_attr);
-    msg_didout = false;
-    msg_starthere();
+    if (p == NULL) {
+      p = prompt;
+    } else {
+      p++;
+      msg_start();
+      msg_clr_eos();
+      msg_puts_attr_len(prompt, p - prompt, echo_attr);
+      msg_didout = false;
+      msg_starthere();
+    }
   }
   cmdline_row = msg_row;
 

src/nvim/ex_getln.c

@@ -3114,11 +3114,17 @@ static void redrawcmdprompt(void)
     }
   }
   if (ccline.cmdprompt != NULL) {
-    msg_puts_attr((const char *)ccline.cmdprompt, ccline.cmdattr);
-    ccline.cmdindent = msg_col + (msg_row - cmdline_row) * Columns;
-    /* do the reverse of set_cmdspos() */
-    if (ccline.cmdfirstc != NUL)
-      --ccline.cmdindent;
+    if (cmdline_external) {
+      Array args = ARRAY_DICT_INIT;
+      ADD(args, STRING_OBJ(cstr_to_string((char *)(ccline.cmdprompt))));
+      ui_event("cmdline_prompt", args);
+    } else {
+      msg_puts_attr((const char *)ccline.cmdprompt, ccline.cmdattr);
+      ccline.cmdindent = msg_col + (msg_row - cmdline_row) * Columns;
+      /* do the reverse of set_cmdspos() */
+      if (ccline.cmdfirstc != NUL)
+        --ccline.cmdindent;
+    }
   } else
     for (i = ccline.cmdindent; i > 0; --i)
       msg_putchar(' ');
@@ -6036,3 +6042,8 @@ void cmdline_set_external(bool external)
 {
   cmdline_external = external;
 }
+
+bool cmdline_get_external(void)
+{
+  return cmdline_external;
+}