From c85313bac7e6e0bb4551dc702e8b08574fa80d43 Mon Sep 17 00:00:00 2001
From: luukvbaal <luukvbaal@gmail.com>
Date: Tue, 3 Feb 2026 13:52:03 +0100
Subject: [PATCH] fix(messages): always assign msg_id to msg_show events #37671

Problem:  Internal messages do not have an ID, which is unexpected and
          undocumented.
Solution: Always assign a msg_id to msg_show events, simplifying
          logic/expectations for UIs.
---
 src/nvim/message.c                   | 21 ++++++++++-----------
 test/functional/ui/messages_spec.lua |  4 +++-
 2 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/src/nvim/message.c b/src/nvim/message.c
index fcf85a3c84..a3f7e37047 100644
--- a/src/nvim/message.c
+++ b/src/nvim/message.c
@@ -152,7 +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 MsgID msg_ext_id = { .type = kObjectTypeInteger, .data.integer = 0 };
+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);
 static sattr_T msg_ext_last_attr = -1;
@@ -365,12 +365,10 @@ MsgID msg_multihl(MsgID id, HlMessage hl_msg, const char *kind, bool history, bo
 
   // provide a new id if not given
   if (id.type == kObjectTypeNil) {
-    id = INTEGER_OBJ(msg_id_next++);
+    id = INTEGER_OBJ(msg_id_next);
   } else if (id.type == kObjectTypeInteger) {
-    id = id.data.integer > 0 ? id : INTEGER_OBJ(msg_id_next++);
-    if (msg_id_next < id.data.integer) {
-      msg_id_next = id.data.integer + 1;
-    }
+    id = id.data.integer > 0 ? id : INTEGER_OBJ(msg_id_next);
+    msg_id_next = MAX(msg_id_next, id.data.integer);
   }
   msg_ext_id = id;
 
@@ -395,7 +393,7 @@ MsgID msg_multihl(MsgID id, HlMessage hl_msg, const char *kind, bool history, bo
   }
 
   if (history && kv_size(hl_msg)) {
-    msg_hist_add_multihl(id, hl_msg, false, msg_data);
+    msg_hist_add_multihl(hl_msg, false, msg_data);
   }
 
   msg_ext_skip_flush = false;
@@ -1107,7 +1105,7 @@ static void msg_hist_add(const char *s, int len, int hl_id)
 
   HlMessage msg = KV_INITIAL_VALUE;
   kv_push(msg, ((HlMessageChunk){ text, hl_id }));
-  msg_hist_add_multihl(INTEGER_OBJ(0), msg, false, NULL);
+  msg_hist_add_multihl(msg, false, NULL);
 }
 
 static bool do_clear_hist_temp = true;
@@ -1138,7 +1136,7 @@ void do_autocmd_progress(MsgID msg_id, HlMessage msg, MessageData *msg_data)
   kv_destroy(messages);
 }
 
-static void msg_hist_add_multihl(MsgID msg_id, HlMessage msg, bool temp, MessageData *msg_data)
+static void msg_hist_add_multihl(HlMessage msg, bool temp, MessageData *msg_data)
 {
   if (do_clear_hist_temp) {
     msg_hist_clear_temp();
@@ -3319,14 +3317,15 @@ void msg_ext_ui_flush(void)
         xfree(chunk);
       }
       xfree(tofree->items);
-      msg_hist_add_multihl(INTEGER_OBJ(0), msg, true, NULL);
+      msg_hist_add_multihl(msg, true, NULL);
     }
     xfree(tofree);
     msg_ext_overwrite = false;
     msg_ext_history = false;
     msg_ext_append = false;
     msg_ext_kind = NULL;
-    msg_ext_id = INTEGER_OBJ(0);
+    msg_id_next += (msg_ext_id.data.integer == msg_id_next);
+    msg_ext_id = INTEGER_OBJ(msg_id_next);
   }
 }
 
diff --git a/test/functional/ui/messages_spec.lua b/test/functional/ui/messages_spec.lua
index b964fded27..dbc84e9c11 100644
--- a/test/functional/ui/messages_spec.lua
+++ b/test/functional/ui/messages_spec.lua
@@ -3608,12 +3608,14 @@ describe('progress-message', function()
     )
     eq('str-id', id7)
 
+    -- internal messages are also assigned an ID (and thus advance the next progress ID)
+    feed('Q')
     local id8 = api.nvim_echo(
       { { 'test-message 30' } },
       true,
       { kind = 'progress', title = 'TestSuit', percent = 30, status = 'running' }
     )
-    eq(12, id8)
+    eq(13, id8)
   end)
 
   it('supports string ids', function()