Improve signature help performance (#2329)

plugin/documents.py

@@ -566,16 +566,17 @@ def do_signature_help_async(self, manual: bool) -> None:
             language_map = session.markdown_language_id_to_st_syntax_map()
             request = Request.signatureHelp(params, self.view)
             session.send_request_async(request, lambda resp: self._on_signature_help(resp, pos, language_map))
-        elif self.view.match_selector(pos, "meta.function-call.arguments"):
-            # Don't force close the signature help popup while the user is typing the parameters.
-            # See also: https://github.com/sublimehq/sublime_text/issues/5518
-            pass
-        else:
-            # TODO: Refactor popup usage to a common class. We now have sigHelp, completionDocs, hover, and diags
-            # all using a popup. Most of these systems assume they have exclusive access to a popup, while in
-            # reality there is only one popup per view.
-            self.view.hide_popup()
-            self._sighelp = None
+        elif self._sighelp:
+            if self.view.match_selector(pos, "meta.function-call.arguments"):
+                # Don't force close the signature help popup while the user is typing the parameters.
+                # See also: https://github.com/sublimehq/sublime_text/issues/5518
+                pass
+            else:
+                # TODO: Refactor popup usage to a common class. We now have sigHelp, completionDocs, hover, and diags
+                # all using a popup. Most of these systems assume they have exclusive access to a popup, while in
+                # reality there is only one popup per view.
+                self.view.hide_popup()
+                self._sighelp = None
 
     def _get_signature_help_session(self) -> Optional[Session]:
         # NOTE: We take the beginning of the region to check the previous char (see last_char variable). This is for