Use set instead of list for exclude in filter_excluded_fields fucntion (#972)

* refactor: use set instead of list for exclude

* Update AUTHORS and CHANGELOG

---------

Co-authored-by: Steven Loria <[email protected]>

Author: allrob23

AUTHORS.rst

@@ -85,3 +85,4 @@ Contributors (chronological)
 - `<https://github.com/kolditz-senec >`_
 - Theron Luhn `@luhn <https://github.com/luhn>`_
 - Robert Shepley `@ShepleySound <https://github.com/ShepleySound>`_
+- Robin `@allrob23 <https://github.com/allrob23>`_

CHANGELOG.rst

@@ -1,6 +1,12 @@
 Changelog
 ---------
 
+(unreleased)
+************
+
+- Perf improvement to ``filter_excluded_fields`` (:issue:`972`).
+  Thanks :user:`allrob23` for the PR.
+
 6.8.1 (2025-01-07)
 ******************
 

src/apispec/ext/marshmallow/common.py

@@ -95,9 +95,9 @@ def filter_excluded_fields(
     :param Meta: the schema's Meta class
     :param bool exclude_dump_only: whether to filter dump_only fields
     """
-    exclude = list(getattr(Meta, "exclude", []))
+    exclude = set(getattr(Meta, "exclude", []))
     if exclude_dump_only:
-        exclude.extend(getattr(Meta, "dump_only", []))
+        exclude.update(getattr(Meta, "dump_only", []))
 
     filtered_fields = {
         key: value