fix(ui): fix some cases of stale highlight definitions

fixes #20695

2 files changed, 21 insertions, 0 deletions

diff --git a/src/nvim/decoration_provider.c b/src/nvim/decoration_provider.c
index 48664421a3..f356efffdc 100644
--- a/src/nvim/decoration_provider.c
+++ b/src/nvim/decoration_provider.c
@@ -194,6 +194,25 @@ void decor_providers_invoke_end(DecorProviders *providers, char **err)
   }
 }
 
+/// Mark all cached state of per-namespace highlights as invalid. Revalidate
+/// current namespace.
+///
+/// Expensive! Should on be called by an already throttled validity check
+/// like highlight_changed() (throttled to the next redraw or mode change)
+void decor_provider_invalidate_hl(void)
+{
+  size_t len = kv_size(decor_providers);
+  for (size_t i = 0; i < len; i++) {
+    DecorProvider *item = &kv_A(decor_providers, i);
+    item->hl_cached = false;
+  }
+
+  if (ns_hl_active) {
+    ns_hl_active = -1;
+    hl_check_ns();
+  }
+}
+
 DecorProvider *get_decor_provider(NS ns_id, bool force)
 {
   assert(ns_id > 0);
diff --git a/src/nvim/highlight_group.c b/src/nvim/highlight_group.c
index 3c3c834c6c..65e3073303 100644
--- a/src/nvim/highlight_group.c
+++ b/src/nvim/highlight_group.c
@@ -2073,6 +2073,8 @@ void highlight_changed(void)
     }
   }
   highlight_ga.ga_len = hlcnt;
+
+  decor_provider_invalidate_hl();
 }
 
 /// Handle command line completion for :highlight command.