PYTHON-4353 Make dns import optional but required for tests (#1588)

Author: blink1073

pymongo/srv_resolver.py

@@ -25,10 +25,15 @@
 
 if TYPE_CHECKING:
     from dns import resolver
+
+    _HAVE_DNSPYTHON = True
 else:
-    resolver = lazy_import("dns.resolver")
+    try:
+        resolver = lazy_import("dns.resolver")
 
-_HAVE_DNSPYTHON = True
+        _HAVE_DNSPYTHON = True
+    except ImportError:
+        _HAVE_DNSPYTHON = False
 
 
 # dnspython can return bytes or str from various parts

test/test_client.py

@@ -110,7 +110,6 @@
 from pymongo.server_selectors import readable_server_selector, writable_server_selector
 from pymongo.server_type import SERVER_TYPE
 from pymongo.settings import TOPOLOGY_TYPE
-from pymongo.srv_resolver import _HAVE_DNSPYTHON
 from pymongo.topology import _ErrorContext
 from pymongo.topology_description import TopologyDescription
 from pymongo.write_concern import WriteConcern
@@ -455,7 +454,6 @@ def test_uri_option_precedence(self):
         self.assertEqual(clopts.replica_set_name, "newname")
         self.assertEqual(clopts.read_preference, ReadPreference.SECONDARY_PREFERRED)
 
-    @unittest.skipUnless(_HAVE_DNSPYTHON, "DNS-related tests need dnspython to be installed")
     def test_connection_timeout_ms_propagates_to_DNS_resolver(self):
         # Patch the resolver.
         from pymongo.srv_resolver import _resolve
@@ -1755,7 +1753,6 @@ def test_process_periodic_tasks(self):
         with self.assertRaises(InvalidOperation):
             coll.insert_many([{} for _ in range(5)])
 
-    @unittest.skipUnless(_HAVE_DNSPYTHON, "DNS-related tests need dnspython to be installed")
     def test_service_name_from_kwargs(self):
         client = MongoClient(
             "mongodb+srv://user:password@test22.test.build.10gen.cc",
@@ -1776,7 +1773,6 @@ def test_service_name_from_kwargs(self):
         )
         self.assertEqual(client._topology_settings.srv_service_name, "customname")
 
-    @unittest.skipUnless(_HAVE_DNSPYTHON, "DNS-related tests need dnspython to be installed")
     def test_srv_max_hosts_kwarg(self):
         client = MongoClient("mongodb+srv://test1.test.build.10gen.cc/")
         self.assertGreater(len(client.topology_description.server_descriptions()), 1)
@@ -1787,11 +1783,6 @@ def test_srv_max_hosts_kwarg(self):
         )
         self.assertEqual(len(client.topology_description.server_descriptions()), 2)
 
-    @unittest.skipIf(_HAVE_DNSPYTHON, "dnspython must not be installed")
-    def test_srv_no_dnspython_error(self):
-        with self.assertRaisesRegex(ConfigurationError, 'The "dnspython" module must be'):
-            MongoClient("mongodb+srv://test1.test.build.10gen.cc/")
-
     @unittest.skipIf(
         client_context.load_balancer or client_context.serverless,
         "loadBalanced clients do not run SDAM",

test/test_dns.py

@@ -28,7 +28,6 @@
 from pymongo.common import validate_read_preference_tags
 from pymongo.errors import ConfigurationError
 from pymongo.mongo_client import MongoClient
-from pymongo.srv_resolver import _HAVE_DNSPYTHON
 from pymongo.uri_parser import parse_uri, split_hosts
 
 
@@ -65,8 +64,6 @@ def setUp(self):
 
 def create_test(test_case):
     def run_test(self):
-        if not _HAVE_DNSPYTHON:
-            raise unittest.SkipTest("DNS tests require the dnspython module")
         uri = test_case["uri"]
         seeds = test_case.get("seeds")
         num_seeds = test_case.get("numSeeds", len(seeds or []))
@@ -161,7 +158,6 @@ def create_tests(cls):
 
 
 class TestParsingErrors(unittest.TestCase):
-    @unittest.skipUnless(_HAVE_DNSPYTHON, "DNS tests require the dnspython module")
     def test_invalid_host(self):
         self.assertRaisesRegex(
             ConfigurationError,
@@ -190,7 +186,6 @@ def test_invalid_host(self):
 
 
 class TestCaseInsensitive(IntegrationTest):
-    @unittest.skipUnless(_HAVE_DNSPYTHON, "DNS tests require the dnspython module")
     def test_connect_case_insensitive(self):
         client = MongoClient("mongodb+srv://TEST1.TEST.BUILD.10GEN.cc/")
         self.addCleanup(client.close)

test/test_srv_polling.py

@@ -95,8 +95,6 @@ class TestSrvPolling(unittest.TestCase):
     CONNECTION_STRING = "mongodb+srv://test1.test.build.10gen.cc"
 
     def setUp(self):
-        if not _HAVE_DNSPYTHON:
-            raise unittest.SkipTest("SRV polling tests require the dnspython module")
         # Patch timeouts to ensure short rescan SRV interval.
         self.client_knobs = client_knobs(
             heartbeat_frequency=WAIT_TIME,
@@ -150,6 +148,7 @@ def predicate():
         return True
 
     def run_scenario(self, dns_response, expect_change):
+        self.assertEqual(_HAVE_DNSPYTHON, True)
         if callable(dns_response):
             dns_resolver_response = dns_response
         else:

test/test_uri_spec.py

@@ -28,7 +28,6 @@
 
 from pymongo.common import INTERNAL_URI_OPTION_NAME_MAP, validate
 from pymongo.compression_support import _HAVE_SNAPPY
-from pymongo.srv_resolver import _HAVE_DNSPYTHON
 from pymongo.uri_parser import SRV_SCHEME, parse_uri
 
 CONN_STRING_TEST_PATH = os.path.join(
@@ -98,8 +97,6 @@ def run_scenario(self):
         compressors = (test.get("options") or {}).get("compressors", [])
         if "snappy" in compressors and not _HAVE_SNAPPY:
             self.skipTest("This test needs the snappy module.")
-        if test["uri"].startswith(SRV_SCHEME) and not _HAVE_DNSPYTHON:
-            self.skipTest("This test needs dnspython package.")
         valid = True
         warning = False
         expected_warning = test.get("warning", False)