From 8aca47e25dd406a39efebc28019db0226b6ec9aa Mon Sep 17 00:00:00 2001
From: Jalil SA <ssergio.jalil@gmail.com>
Date: Tue, 7 Mar 2023 03:26:59 -0600
Subject: [PATCH] Add setdefault to BaseSettings (#5821)

---
 scrapy/settings/__init__.py     |  7 +++++++
 tests/test_settings/__init__.py | 13 +++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/scrapy/settings/__init__.py b/scrapy/settings/__init__.py
index fde8fdde4..a3b849f7b 100644
--- a/scrapy/settings/__init__.py
+++ b/scrapy/settings/__init__.py
@@ -293,6 +293,13 @@ class BaseSettings(MutableMapping):
         else:
             self.attributes[name].set(value, priority)
 
+    def setdefault(self, name, default=None, priority="project"):
+        if name not in self:
+            self.set(name, default, priority)
+            return default
+
+        return self.attributes[name].value
+
     def setdict(self, values, priority="project"):
         self.update(values, priority)
 
diff --git a/tests/test_settings/__init__.py b/tests/test_settings/__init__.py
index 3e8187096..4a577cd8c 100644
--- a/tests/test_settings/__init__.py
+++ b/tests/test_settings/__init__.py
@@ -65,6 +65,19 @@ class BaseSettingsTest(unittest.TestCase):
     def setUp(self):
         self.settings = BaseSettings()
 
+    def test_setdefault_not_existing_value(self):
+        settings = BaseSettings()
+        value = settings.setdefault("TEST_OPTION", "value")
+        self.assertEqual(settings["TEST_OPTION"], "value")
+        self.assertEqual(value, "value")
+        self.assertIsNotNone(value)
+
+    def test_setdefault_existing_value(self):
+        settings = BaseSettings({"TEST_OPTION": "value"})
+        value = settings.setdefault("TEST_OPTION", None)
+        self.assertEqual(settings["TEST_OPTION"], "value")
+        self.assertEqual(value, "value")
+
     def test_set_new_attribute(self):
         self.settings.set("TEST_OPTION", "value", 0)
         self.assertIn("TEST_OPTION", self.settings.attributes)