Fixed #37075 -- Allowed overriding the PostgreSQL pool's "check" callable.HEADmain

Setting "check" in OPTIONS["pool"] previously raised TypeError because the
PostgreSQL backend always passed check= to ConnectionPool() and unpacked
**pool_options on top, regardless of CONN_HEALTH_CHECKS. The user's callable
now takes precedence via setdefault(); pool_options is copied first to avoid
mutating the user's settings dict.

3 files changed, 33 insertions, 1 deletions

diff --git a/AUTHORS b/AUTHORS
index 07c87068a9..8182862607 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -891,6 +891,7 @@ answer newbie questions, and generally made Django that much better:
     Ramon Saraiva <ramonsaraiva@gmail.com>
     Ram Rachum <ram@rachum.com>
     Randy Barlow <randy@electronsweatshop.com>
+    Raoni Timo <raoni@relume.io>
     Raphaël Barrois <raphael.barrois@m4x.org>
     Raphael Michel <mail@raphaelmichel.de>
     Raúl Cumplido <raulcumplido@gmail.com>
diff --git a/django/db/backends/postgresql/base.py b/django/db/backends/postgresql/base.py
index 42b37ab3c2..16cf7f84e6 100644
--- a/django/db/backends/postgresql/base.py
+++ b/django/db/backends/postgresql/base.py
@@ -216,11 +216,15 @@ class DatabaseWrapper(BaseDatabaseWrapper):
             # Ensure we run in autocommit, Django properly sets it later on.
             connect_kwargs["autocommit"] = True
             enable_checks = self.settings_dict["CONN_HEALTH_CHECKS"]
+            # Copy to avoid mutating the user's settings dict.
+            pool_options = {**pool_options}
+            pool_options.setdefault(
+                "check", ConnectionPool.check_connection if enable_checks else None
+            )
             pool = ConnectionPool(
                 kwargs=connect_kwargs,
                 open=False,  # Do not open the pool during startup.
                 configure=self._configure_connection,
-                check=ConnectionPool.check_connection if enable_checks else None,
                 **pool_options,
             )
             # setdefault() ensures that multiple threads don't set this in
diff --git a/tests/backends/postgresql/tests.py b/tests/backends/postgresql/tests.py
index e03c37cb57..9afa6020a3 100644
--- a/tests/backends/postgresql/tests.py
+++ b/tests/backends/postgresql/tests.py
@@ -326,6 +326,33 @@ class Tests(TestCase):
             new_connection.close_pool()
 
     @unittest.skipUnless(is_psycopg3, "psycopg3 specific test")
+    def test_pool_check_can_be_overridden(self):
+        def custom_check(conn):
+            pass
+
+        new_connection = no_pool_connection(alias="default_pool")
+        new_connection.settings_dict["OPTIONS"]["pool"] = {"check": custom_check}
+
+        for enable_checks in (True, False):
+            with self.subTest(CONN_HEALTH_CHECKS=enable_checks):
+                new_connection.settings_dict["CONN_HEALTH_CHECKS"] = enable_checks
+                try:
+                    self.assertIs(new_connection.pool._check, custom_check)
+                finally:
+                    new_connection.close_pool()
+
+    @unittest.skipUnless(is_psycopg3, "psycopg3 specific test")
+    def test_pool_options_not_mutated(self):
+        pool_options = {"min_size": 0, "max_size": 2}
+        new_connection = no_pool_connection(alias="default_pool")
+        new_connection.settings_dict["OPTIONS"]["pool"] = pool_options
+        try:
+            self.assertIsNotNone(new_connection.pool)
+        finally:
+            new_connection.close_pool()
+        self.assertEqual(pool_options, {"min_size": 0, "max_size": 2})
+
+    @unittest.skipUnless(is_psycopg3, "psycopg3 specific test")
     def test_cannot_open_new_connection_in_atomic_block(self):
         new_connection = no_pool_connection(alias="default_pool")
         new_connection.settings_dict["OPTIONS"]["pool"] = True