PYTHON-4407 Eagerly import dnspython (#1622)

Author: blink1073

pymongo/srv_resolver.py

@@ -17,23 +17,17 @@
 
 import ipaddress
 import random
-from typing import TYPE_CHECKING, Any, Optional, Union
+from typing import Any, Optional, Union
 
-from pymongo._lazy_import import lazy_import
 from pymongo.common import CONNECT_TIMEOUT
 from pymongo.errors import ConfigurationError
 
-if TYPE_CHECKING:
+try:
     from dns import resolver
 
     _HAVE_DNSPYTHON = True
-else:
-    try:
-        resolver = lazy_import("dns.resolver")
-
-        _HAVE_DNSPYTHON = True
-    except ImportError:
-        _HAVE_DNSPYTHON = False
+except ImportError:
+    _HAVE_DNSPYTHON = False
 
 
 # dnspython can return bytes or str from various parts

test/test_srv_polling.py

@@ -345,6 +345,12 @@ def resolver_response():
                 AssertionError, self.assert_nodelist_change, modified, client, timeout=WAIT_TIME / 2
             )
 
+    def test_import_dns_resolver(self):
+        # Regression test for PYTHON-4407
+        import dns.resolver
+
+        self.assertTrue(hasattr(dns.resolver, "resolve"))
+
 
 if __name__ == "__main__":
     unittest.main()