Move IO out of __init__

Author: aclark4life

pymongo/asynchronous/srv_resolver.py

@@ -133,6 +133,11 @@ async def _get_srv_response_and_hosts(
     ) -> tuple[resolver.Answer, list[tuple[str, Any]]]:
         results = await self._resolve_uri(encapsulate_errors)
 
+        if self.__fqdn == results[0].target.to_text():
+            raise ConfigurationError(
+                "Invalid SRV host: return address is identical to SRV hostname"
+            )
+
         # Construct address tuples
         nodes = [
             (maybe_decode(res.target.to_text(omit_final_dot=True)), res.port)  # type: ignore[attr-defined]

pymongo/synchronous/srv_resolver.py

@@ -133,6 +133,11 @@ def _get_srv_response_and_hosts(
     ) -> tuple[resolver.Answer, list[tuple[str, Any]]]:
         results = self._resolve_uri(encapsulate_errors)
 
+        if self.__fqdn == results[0].target.to_text():
+            raise ConfigurationError(
+                "Invalid SRV host: return address is identical to SRV hostname"
+            )
+
         # Construct address tuples
         nodes = [
             (maybe_decode(res.target.to_text(omit_final_dot=True)), res.port)  # type: ignore[attr-defined]

test/test_uri_parser.py

@@ -588,7 +588,7 @@ def test_error_when_return_address_does_not_end_with_srv_domain(self):
             },
             {
                 "query": "_mongodb._tcp.mongo.local",
-                "mock_target": "mongo.local",
+                "mock_target": "foo.mongo.local",
                 "expected_error": "Invalid SRV host",
             },
         ]