From cc627f7ba3bfb667b63df0cfd297dd456972d447 Mon Sep 17 00:00:00 2001
From: Oleh Prypin <oleh@pryp.in>
Date: Sat, 24 Sep 2022 23:06:18 +0200
Subject: [PATCH] Prevent wrapping into Optional when the option has a default

---
 mkdocs/config/config_options.py             | 7 ++++++-
 mkdocs/tests/config/config_options_tests.py | 4 ++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/mkdocs/config/config_options.py b/mkdocs/config/config_options.py
index b76af0a7..211c0be4 100644
--- a/mkdocs/config/config_options.py
+++ b/mkdocs/config/config_options.py
@@ -429,6 +429,11 @@ class Optional(Generic[T], BaseConfigOption[Union[T, None]]):
     """
 
     def __init__(self, config_option: BaseConfigOption[T]):
+        if config_option.default is not None:
+            raise ValueError(
+                f"This option already has a default ({config_option.default!r}) "
+                f"and doesn't need to be wrapped into Optional"
+            )
         super().__init__()
         self.option = config_option
         self.warnings = config_option.warnings
@@ -443,7 +448,7 @@ class Optional(Generic[T], BaseConfigOption[Union[T, None]]):
 
     def run_validation(self, value):
         if value is None:
-            return self.default
+            return None
         return self.option.validate(value)
 
     def post_validation(self, config, key_name):
diff --git a/mkdocs/tests/config/config_options_tests.py b/mkdocs/tests/config/config_options_tests.py
index b64bf827..71b3b14e 100644
--- a/mkdocs/tests/config/config_options_tests.py
+++ b/mkdocs/tests/config/config_options_tests.py
@@ -95,6 +95,10 @@ class TypeTest(TestCase):
         ):
             self.get_config(Schema, {'option': "Testing Long"})
 
+    def test_optional_with_default(self) -> None:
+        with self.assertRaisesRegex(ValueError, "doesn't need to be wrapped into Optional"):
+            c.Optional(c.Type(int, default=5))
+
 
 class ChoiceTest(TestCase):
     def test_required(self) -> None: