fix(log): unify error messages for vim.ui_attach/decor providers #33005

Problem:  Error messages that cause a vim.ui_attach() namespace to
          detach are not visible in the message history. Decoration
          provider and vim.ui_attach error messages are dissimilar.
Solution: Emit vim.ui_attach() errors as an actual message in addition
          to logging it. Adjust error message format.

3 files changed, 20 insertions, 10 deletions

diff --git a/src/nvim/decoration_provider.c b/src/nvim/decoration_provider.c
index 2dbf8dd5d9..902e995ad5 100644
--- a/src/nvim/decoration_provider.c
+++ b/src/nvim/decoration_provider.c
@@ -23,8 +23,6 @@
 # include "decoration_provider.c.generated.h"
 #endif
 
-enum { DP_MAX_ERROR = 3, };
-
 static kvec_t(DecorProvider) decor_providers = KV_INITIAL_VALUE;
 
 #define DECORATION_PROVIDER_INIT(ns_id) (DecorProvider) \
@@ -34,9 +32,9 @@ static kvec_t(DecorProvider) decor_providers = KV_INITIAL_VALUE;
 
 static void decor_provider_error(DecorProvider *provider, const char *name, const char *msg)
 {
-  const char *ns_name = describe_ns(provider->ns_id, "(UNKNOWN PLUGIN)");
-  ILOG("error in provider %s.%s: %s", ns_name, name, msg);
-  msg_schedule_semsg_multiline("Error in decoration provider %s.%s:\n%s", ns_name, name, msg);
+  const char *ns = describe_ns(provider->ns_id, "(UNKNOWN PLUGIN)");
+  ELOG("Error in decoration provider \"%s\" (ns=%s):\n%s", name, ns, msg);
+  msg_schedule_semsg_multiline("Error in decoration provider \"%s\" (ns=%s):\n%s", name, ns, msg);
 }
 
 // Note we pass in a provider index as this function may cause decor_providers providers to be
@@ -59,11 +57,11 @@ static bool decor_provider_invoke(int provider_idx, const char *name, LuaRef ref
     return true;
   }
 
-  if (ERROR_SET(&err) && provider->error_count < DP_MAX_ERROR) {
+  if (ERROR_SET(&err) && provider->error_count < CB_MAX_ERROR) {
     decor_provider_error(provider, name, err.msg);
     provider->error_count++;
 
-    if (provider->error_count >= DP_MAX_ERROR) {
+    if (provider->error_count >= CB_MAX_ERROR) {
       provider->state = kDecorProviderDisabled;
     }
   }
diff --git a/src/nvim/lua/executor.h b/src/nvim/lua/executor.h
index 9ff869e221..557c0b025e 100644
--- a/src/nvim/lua/executor.h
+++ b/src/nvim/lua/executor.h
@@ -44,6 +44,9 @@ typedef enum {
   kRetLuaref,  ///< return value becomes a single Luaref, regardless of type (except NIL)
 } LuaRetMode;
 
+/// Maximum number of errors in vim.ui_attach() and decor provider callbacks.
+enum { CB_MAX_ERROR = 3, };
+
 /// To use with kRetNilBool for quick truthiness check
 #define LUARET_TRUTHY(res) ((res).type == kObjectTypeBoolean && (res).data.boolean == true)
 
diff --git a/src/nvim/ui.c b/src/nvim/ui.c
index 51815c36e1..e203e66ad1 100644
--- a/src/nvim/ui.c
+++ b/src/nvim/ui.c
@@ -6,6 +6,7 @@
 #include <string.h>
 #include <uv.h>
 
+#include "nvim/api/extmark.h"
 #include "nvim/api/private/helpers.h"
 #include "nvim/api/private/validate.h"
 #include "nvim/api/ui.h"
@@ -712,6 +713,13 @@ void ui_grid_resize(handle_T grid_handle, int width, int height, Error *err)
   }
 }
 
+static void ui_attach_error(uint32_t ns_id, const char *name, const char *msg)
+{
+  const char *ns = describe_ns((NS)ns_id, "(UNKNOWN PLUGIN)");
+  ELOG("Error in \"%s\" UI event handler (ns=%s):\n%s", name, ns, msg);
+  msg_schedule_semsg_multiline("Error in \"%s\" UI event handler (ns=%s):\n%s", name, ns, msg);
+}
+
 void ui_call_event(char *name, bool fast, Array args)
 {
   bool handled = false;
@@ -735,7 +743,7 @@ void ui_call_event(char *name, bool fast, Array args)
       handled = true;
     }
     if (ERROR_SET(&err)) {
-      ELOG("Error executing UI event callback: %s", err.msg);
+      ui_attach_error(ns_id, name, err.msg);
       ui_remove_cb(ns_id, true);
     }
     api_clear_error(&err);
@@ -792,13 +800,14 @@ void ui_add_cb(uint32_t ns_id, LuaRef cb, bool *ext_widgets)
 void ui_remove_cb(uint32_t ns_id, bool checkerr)
 {
   UIEventCallback *item = pmap_get(uint32_t)(&ui_event_cbs, ns_id);
-  if (item && (!checkerr || ++item->errors > 10)) {
+  if (item && (!checkerr || ++item->errors > CB_MAX_ERROR)) {
     pmap_del(uint32_t)(&ui_event_cbs, ns_id, NULL);
     free_ui_event_callback(item);
     ui_cb_update_ext();
     ui_refresh();
     if (checkerr) {
-      msg_schedule_semsg("Excessive errors in vim.ui_attach() callback from ns: %d.", ns_id);
+      const char *ns = describe_ns((NS)ns_id, "(UNKNOWN PLUGIN)");
+      msg_schedule_semsg("Excessive errors in vim.ui_attach() callback (ns=%s)", ns);
     }
   }
 }