fix(messages): incorrect error message splitting and kind #32990

Problem:  Message kind logic for emitting an error message is convoluted
          and still results in emitting an unfinished message earlier than
          wanted.
Solution: Ensure emsg_multiline() always sets the kind wanted by the caller
          and doesn't isn't unset to logic for emitting the source message.
          Caller is responsible for making sure multiple message chunks are
          not emitted as multiple events by setting `msg_ext_skip_flush`...

9 files changed, 29 insertions, 39 deletions

diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 03713aa262..edb77778a3 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -368,7 +368,7 @@ static void api_wrapper(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
   Object result = handler.fn(VIML_INTERNAL_CALL, args, &arena, &err);
 
   if (ERROR_SET(&err)) {
-    semsg_multiline(e_api_error, err.msg);
+    semsg_multiline("emsg", e_api_error, err.msg);
     goto end;
   }
 
@@ -6414,12 +6414,11 @@ static void f_rpcrequest(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
     if (chan) {
       name = get_client_info(chan, "name");
     }
-    msg_ext_set_kind("rpc_error");
     if (name) {
-      semsg_multiline("Error invoking '%s' on channel %" PRIu64 " (%s):\n%s",
+      semsg_multiline("rpc_error", "Error invoking '%s' on channel %" PRIu64 " (%s):\n%s",
                       method, chan_id, name, err.msg);
     } else {
-      semsg_multiline("Error invoking '%s' on channel %" PRIu64 ":\n%s",
+      semsg_multiline("rpc_error", "Error invoking '%s' on channel %" PRIu64 ":\n%s",
                       method, chan_id, err.msg);
     }
 
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index af93db9956..640c729e3b 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -7804,7 +7804,7 @@ static void ex_checkhealth(exarg_T *eap)
       emsg(_("E5009: Invalid 'runtimepath'"));
     }
   }
-  semsg_multiline(err.msg);
+  semsg_multiline("emsg", err.msg);
   api_clear_error(&err);
 }
 
diff --git a/src/nvim/getchar.c b/src/nvim/getchar.c
index 899293e9f6..ec6e5f8b5d 100644
--- a/src/nvim/getchar.c
+++ b/src/nvim/getchar.c
@@ -3254,7 +3254,7 @@ bool map_execute_lua(bool may_repeat)
   Array args = ARRAY_DICT_INIT;
   nlua_call_ref(ref, NULL, args, kRetNilBool, NULL, &err);
   if (ERROR_SET(&err)) {
-    semsg_multiline("E5108: %s", err.msg);
+    semsg_multiline("emsg", "E5108: %s", err.msg);
     api_clear_error(&err);
   }
 
diff --git a/src/nvim/lua/executor.c b/src/nvim/lua/executor.c
index 724a3d77e6..49ff5679e2 100644
--- a/src/nvim/lua/executor.c
+++ b/src/nvim/lua/executor.c
@@ -160,8 +160,7 @@ void nlua_error(lua_State *const lstate, const char *const msg)
     fprintf(stderr, msg, (int)len, str);
     fprintf(stderr, "\n");
   } else {
-    msg_ext_set_kind("lua_error");
-    semsg_multiline(msg, (int)len, str);
+    semsg_multiline("lua_error", msg, (int)len, str);
   }
 
   lua_pop(lstate, 1);
@@ -191,16 +190,15 @@ static void nlua_luv_error_event(void **argv)
 {
   char *error = (char *)argv[0];
   luv_err_t type = (luv_err_t)(intptr_t)argv[1];
-  msg_ext_set_kind("lua_error");
   switch (type) {
   case kCallback:
-    semsg_multiline("Error executing callback:\n%s", error);
+    semsg_multiline("lua_error", "Error executing callback:\n%s", error);
     break;
   case kThread:
-    semsg_multiline("Error in luv thread:\n%s", error);
+    semsg_multiline("lua_error", "Error in luv thread:\n%s", error);
     break;
   case kThreadCallback:
-    semsg_multiline("Error in luv callback, thread:\n%s", error);
+    semsg_multiline("lua_error", "Error in luv callback, thread:\n%s", error);
     break;
   default:
     break;
diff --git a/src/nvim/main.c b/src/nvim/main.c
index 7539fbc5d9..50677607eb 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -2064,7 +2064,7 @@ static void do_exrc_initialization(void)
       xfree(str);
       if (ERROR_SET(&err)) {
         semsg("Error detected while processing %s:", VIMRC_LUA_FILE);
-        semsg_multiline(err.msg);
+        semsg_multiline("emsg", err.msg);
         api_clear_error(&err);
       }
     }
diff --git a/src/nvim/mapping.c b/src/nvim/mapping.c
index 2b9a972bc9..ab9d68f911 100644
--- a/src/nvim/mapping.c
+++ b/src/nvim/mapping.c
@@ -1664,7 +1664,7 @@ char *eval_map_expr(mapblock_T *mp, int c)
     }
     api_free_object(ret);
     if (ERROR_SET(&err)) {
-      semsg_multiline("E5108: %s", err.msg);
+      semsg_multiline("emsg", "E5108: %s", err.msg);
       api_clear_error(&err);
     }
   } else {
diff --git a/src/nvim/message.c b/src/nvim/message.c
index a8635f1a61..c210d64845 100644
--- a/src/nvim/message.c
+++ b/src/nvim/message.c
@@ -313,6 +313,7 @@ void msg_multihl(HlMessage hl_msg, const char *kind, bool history, bool err)
     msg_ext_set_kind(kind);
   }
   is_multihl = true;
+  msg_ext_skip_flush = true;
   for (uint32_t i = 0; i < kv_size(hl_msg); i++) {
     HlMessageChunk chunk = kv_A(hl_msg, i);
     if (err) {
@@ -325,6 +326,7 @@ void msg_multihl(HlMessage hl_msg, const char *kind, bool history, bool err)
   if (history && kv_size(hl_msg)) {
     msg_hist_add_multihl(hl_msg, false);
   }
+  msg_ext_skip_flush = false;
   is_multihl = false;
   no_wait_return--;
   msg_end();
@@ -640,9 +642,6 @@ void msg_source(int hl_id)
     msg_scroll = true;  // this will take more than one line
     msg(p, hl_id);
     xfree(p);
-    if (is_multihl) {
-      msg_start();  // avoided in msg_keep() but need the "msg_didout" newline here
-    }
   }
   p = get_emsg_lnum();
   if (p != NULL) {
@@ -656,6 +655,9 @@ void msg_source(int hl_id)
     XFREE_CLEAR(last_sourcing_name);
     if (SOURCING_NAME != NULL) {
       last_sourcing_name = xstrdup(SOURCING_NAME);
+      if (!redirecting()) {
+        msg_putchar_hl('\n', hl_id);
+      }
     }
   }
   no_wait_return--;
@@ -780,21 +782,19 @@ bool emsg_multiline(const char *s, const char *kind, int hl_id, bool multiline)
   }                           // wait_return() has reset need_wait_return
                               // and a redraw is expected because
                               // msg_scrolled is non-zero
-  if (msg_ext_kind == NULL) {
-    msg_ext_set_kind(kind);
-  }
+  msg_ext_set_kind(kind);
 
   // Display name and line number for the source of the error.
   msg_scroll = true;
+  bool save_msg_skip_flush = msg_ext_skip_flush;
+  msg_ext_skip_flush = true;
   msg_source(hl_id);
 
-  if (msg_ext_kind == NULL) {
-    msg_ext_set_kind(kind);
-  }
-
   // Display the error message itself.
   msg_nowait = false;  // Wait for this msg.
-  return msg_keep(s, hl_id, false, multiline);
+  int rv = msg_keep(s, hl_id, false, multiline);
+  msg_ext_skip_flush = save_msg_skip_flush;
+  return rv;
 }
 
 /// emsg() - display an error message
@@ -831,7 +831,7 @@ bool semsg(const char *const fmt, ...)
 
 #define MULTILINE_BUFSIZE 8192
 
-bool semsg_multiline(const char *const fmt, ...)
+bool semsg_multiline(const char *kind, const char *const fmt, ...)
 {
   bool ret;
   va_list ap;
@@ -845,7 +845,7 @@ bool semsg_multiline(const char *const fmt, ...)
   vim_vsnprintf(errbuf, sizeof(errbuf), fmt, ap);
   va_end(ap);
 
-  ret = emsg_multiline(errbuf, "emsg", HLF_E, true);
+  ret = emsg_multiline(errbuf, kind, HLF_E, true);
 
   return ret;
 }
@@ -1431,6 +1431,7 @@ static void hit_return_msg(bool newline_sb)
     msg_putchar('\n');
   }
   p_more = false;       // don't want to see this message when scrolling back
+  msg_ext_skip_flush = false;
   msg_ext_set_kind("return_prompt");
   if (got_int) {
     msg_puts(_("Interrupt: "));
diff --git a/test/functional/lua/ui_event_spec.lua b/test/functional/lua/ui_event_spec.lua
index 8159a4c91c..5dcb13a7d0 100644
--- a/test/functional/lua/ui_event_spec.lua
+++ b/test/functional/lua/ui_event_spec.lua
@@ -362,7 +362,7 @@ describe('vim.ui_attach', function()
       messages = {
         {
           content = { { 'Press ENTER or type command to continue', 100, 18 } },
-          history = true,
+          history = false,
           kind = 'return_prompt',
         },
       },
diff --git a/test/functional/ui/messages_spec.lua b/test/functional/ui/messages_spec.lua
index 1e18cddca1..9b01150411 100644
--- a/test/functional/ui/messages_spec.lua
+++ b/test/functional/ui/messages_spec.lua
@@ -181,20 +181,12 @@ describe('ui/ext_messages', function()
       cmdline = { { abort = false } },
       messages = {
         {
-          content = { { 'Error detected while processing :', 9, 6 } },
-          history = true,
-          kind = 'emsg',
-        },
-        {
-          content = { { 'E605: Exception not caught: foo', 9, 6 } },
+          content = {
+            { 'Error detected while processing :\nE605: Exception not caught: foo', 9, 6 },
+          },
           history = true,
           kind = 'emsg',
         },
-        {
-          content = { { 'Press ENTER or type command to continue', 6, 18 } },
-          history = false,
-          kind = 'return_prompt',
-        },
       },
     }