feat(ui): specify whether msg_show event comes from typed command

Problem:  Unable to tell whether a msg_show event is emitted as a result
          a command typed on the cmdline (UI may want to represent these
          differently from other messages).
Solution: Add trigger parameter that is set to "typed_cmd" for
          a message emitted due to an interactively typed command.
          Possible extensions are mapping/timer/event but it's hard to
          imagine a UI distinguishing those so not added here.

runtime/doc/api-ui-events.txt

@@ -829,9 +829,9 @@ will be set to zero, but can be changed and used for the replacing cmdline or
 message window. Cmdline state is emitted as |ui-cmdline| events, which the UI
 must handle.
 
-["msg_show", kind, content, replace_last, history, append, msg_id] ~
+["msg_show", kind, content, replace_last, history, append, id, trigger] ~
 	Display a message to the user. Update (replace) any existing message
-	matching `msg_id`.
+	matching `id`.
 
 	kind
 	    Name indicating the message kind:
@@ -887,9 +887,14 @@ must handle.
 	    True if the message should be appended to the previous message,
 	    rather than started on a new line. Is set for |:echon|.
 
-	msg_id
+	id
 	    Unique identifier for the message. It can either be an integer or
-	    string. When message of same id appears it should replace the older message.
+	    string. A (visible) message with the same id should be replaced.
+
+	trigger
+	    Type of action that triggered the message:
+		"" (empty)      Unknown (consider a |feature-request|)
+		"typed_cmd"     Interactively typed command on the |cmdline|
 
 ["msg_clear"] ~
 	Clear all messages currently displayed by "msg_show", emitted after

runtime/doc/news.txt

@@ -234,8 +234,7 @@ EVENTS
 • A new `empty` message kind is emitted for an empty (e.g. `:echo ""`) message.
 • |CmdlineLeave| sets |v:char| to the character that stops the Cmdline mode.
 • |CmdlineLeavePre| triggered before preparing to leave the command line.
-• New `append` parameter for |ui-messages| `msg_show` event.
-• New `msg_id` parameter for |ui-messages| `msg_show` event.
+• New `append`, `id` and `trigger` parameter for |ui-messages| `msg_show` event.
 • 'rulerformat' is emitted as `msg_ruler` when not part of the statusline.
 • Creating or updating a progress message with |nvim_echo()| triggers a |Progress| event.
 • |MarkSet| is triggered after a |mark| is set by the user (currently doesn't

src/nvim/api/ui_events.in.h

@@ -165,7 +165,7 @@ void wildmenu_hide(void)
   FUNC_API_SINCE(3) FUNC_API_REMOTE_ONLY;
 
 void msg_show(String kind, Array content, Boolean replace_last, Boolean history, Boolean append,
-              Object id)
+              Object id, String trigger)
   FUNC_API_SINCE(6) FUNC_API_REMOTE_ONLY;
 void msg_clear(void)
   FUNC_API_SINCE(6) FUNC_API_REMOTE_ONLY;

src/nvim/message.c

@@ -152,6 +152,7 @@ bool keep_msg_more = false;    // keep_msg was set by msgmore()
 
 // Extended msg state, currently used for external UIs with ext_messages
 static const char *msg_ext_kind = NULL;
+static const char *msg_ext_trigger = NULL;
 static MsgID msg_ext_id = { .type = kObjectTypeInteger, .data.integer = 1 };
 static Array *msg_ext_chunks = NULL;
 static garray_T msg_ext_last_chunk = GA_INIT(sizeof(char), 40);
@@ -1650,6 +1651,13 @@ void msg_ext_set_kind(const char *msg_kind)
   redir_col = msg_ext_append ? redir_col : 0;
 }
 
+void msg_ext_set_trigger(const char *trigger)
+{
+  // Don't change the trigger of an existing batch:
+  msg_ext_ui_flush();
+  msg_ext_trigger = trigger;
+}
+
 /// Prepare for outputting characters in the command line.
 void msg_start(void)
 {
@@ -2285,7 +2293,7 @@ void msg_puts_len(const char *const str, const ptrdiff_t len, int hl_id, bool hi
   if (msg_silent != 0 || *str == NUL) {
     if (*str == NUL && ui_has(kUIMessages)) {
       ui_call_msg_show(cstr_as_string("empty"), (Array)ARRAY_DICT_INIT, false, false, false,
-                       INTEGER_OBJ(-1));
+                       INTEGER_OBJ(-1), (String)STRING_INIT);
     }
     return;
   }
@@ -3317,7 +3325,7 @@ void msg_ext_ui_flush(void)
     Array *tofree = msg_ext_init_chunks();
 
     ui_call_msg_show(cstr_as_string(msg_ext_kind), *tofree, msg_ext_overwrite, msg_ext_history,
-                     msg_ext_append, msg_ext_id);
+                     msg_ext_append, msg_ext_id, cstr_as_string(msg_ext_trigger));
     // clear info after emitting message.
     if (msg_ext_history) {
       api_free_array(*tofree);

src/nvim/normal.c

@@ -3186,9 +3186,9 @@ static void nv_colon(cmdarg_T *cap)
     }
   }
 
-  // When typing, don't type below an old message
   if (KeyTyped) {
-    compute_cmdrow();
+    msg_ext_set_trigger("typed_cmd");  // distinguish msg_show emitted for typed cmd
+    compute_cmdrow();                  // when typing, don't type below an old message
   }
 
   if (is_lua) {
@@ -3198,6 +3198,7 @@ static void nv_colon(cmdarg_T *cap)
     cmd_result = do_cmdline(NULL, is_cmdkey ? getcmdkeycmd : getexline, NULL,
                             cap->oap->op_type != OP_NOP ? DOCMD_KEEPLINE : 0);
   }
+  msg_ext_set_trigger("");
 
   if (cmd_result == false) {
     // The Ex command failed, do not execute the operator.

test/functional/ui/messages_spec.lua

@@ -1636,6 +1636,34 @@ stack traceback:
       },
     })
   end)
+
+  it('trigger', function()
+    command('echo "foo"')
+    screen:expect({
+      grid = [[
+        ^                         |
+        {1:~                        }|*4
+      ]],
+      messages = { { content = { { 'foo' } }, kind = 'echo', trigger = '' } },
+    })
+    command('map Q :echo "foo"<CR>')
+    feed('Q')
+    screen:expect({
+      grid = [[
+        ^                         |
+        {1:~                        }|*4
+      ]],
+      messages = { { content = { { 'foo' } }, kind = 'echo', trigger = '' } },
+    })
+    feed(':echo "foo"<CR>')
+    screen:expect({
+      grid = [[
+        ^                         |
+        {1:~                        }|*4
+      ]],
+      messages = { { content = { { 'foo' } }, kind = 'echo', trigger = 'typed_cmd' } },
+    })
+  end)
 end)
 
 describe('ui/builtin messages', function()

test/functional/ui/screen.lua

@@ -671,7 +671,7 @@ screen:redraw_debug() to show all intermediate screen states.]]
     -- the ext_ feature being disabled, or the feature currently not activated
     -- (e.g. no external cmdline visible). Some extensions require
     -- preprocessing to represent highlights in a reproducible way.
-    local extstate = self:_extstate_repr(attr_state)
+    local extstate = self:_extstate_repr(attr_state, expected)
     if expected.mode ~= nil then
       extstate.mode = self.mode
     end
@@ -1440,7 +1440,7 @@ function Screen:_handle_wildmenu_hide()
   self.wildmenu_items, self.wildmenu_pos = nil, nil
 end
 
-function Screen:_handle_msg_show(kind, chunks, replace_last, history, append, id, progress)
+function Screen:_handle_msg_show(kind, chunks, replace_last, history, append, id, trigger)
   local pos = #self.messages
   if not replace_last or pos == 0 then
     pos = pos + 1
@@ -1451,7 +1451,7 @@ function Screen:_handle_msg_show(kind, chunks, replace_last, history, append, id
     history = history,
     append = append,
     id = id,
-    progress = progress,
+    trigger = trigger,
   }
 end
 
@@ -1560,7 +1560,7 @@ local function hl_id_to_name(self, id)
   return id and self.hl_names[id] or nil
 end
 
-function Screen:_extstate_repr(attr_state)
+function Screen:_extstate_repr(attr_state, exp)
   local cmdline = {}
   for i, entry in pairs(self.cmdline) do
     entry = shallowcopy(entry)
@@ -1578,13 +1578,18 @@ function Screen:_extstate_repr(attr_state)
 
   local messages = {}
   for i, entry in ipairs(self.messages) do
+    local trigger = nil
+    if exp and exp.messages and exp.messages[i] and exp.messages[i].trigger ~= nil then
+      -- Late addition, only include when expected state includes it.
+      trigger = entry.trigger
+    end
     messages[i] = {
       kind = entry.kind,
       content = self:_chunks_repr(entry.content, attr_state),
       history = entry.history or nil,
       append = entry.append or nil,
       id = entry.kind == 'progress' and entry.id or nil,
-      progress = entry.kind == 'progress' and entry.progress or nil,
+      trigger = trigger,
     }
   end