refactor: Instantiate resolver with API client in Python connector

- Add __init__ to DefaultResolver and DnsResolver to accept client in constructor.
- Remove set_client method from DnsResolver.
- Lazy-initialize self._resolver in Connector.connect_async passing the initialized self._client.
- Update tests to use constructor injection instead of set_client.

Author: Kokoro Connector Build

google/cloud/sql/connector/connector.py

@@ -176,7 +176,8 @@ def __init__(
         self._timeout = timeout
         self._enable_iam_auth = enable_iam_auth
         self._user_agent = user_agent
-        self._resolver = resolver()
+        self._resolver_cls = resolver
+        self._resolver = None
         self._failover_period = failover_period
         # if ip_type is str, convert to IPTypes enum
         if isinstance(ip_type, str):
@@ -316,8 +317,8 @@ async def connect_async(
                 user_agent=self._user_agent,
                 driver=driver,
             )
-            if hasattr(self._resolver, "set_client"):
-                self._resolver.set_client(self._client)
+        if self._resolver is None:
+            self._resolver = self._resolver_cls(client=self._client)
         enable_iam_auth = kwargs.pop("enable_iam_auth", self._enable_iam_auth)
 
         conn_name = await self._resolver.resolve(instance_connection_string)

google/cloud/sql/connector/resolver.py

@@ -13,7 +13,7 @@
 # limitations under the License.
 
 import re
-from typing import Any, List
+from typing import Any, List, Optional
 
 import dns.asyncresolver
 
@@ -33,6 +33,9 @@
 class DefaultResolver:
     """DefaultResolver simply validates and parses instance connection name."""
 
+    def __init__(self, *args: Any, client: Optional[Any] = None, **kwargs: Any) -> None:
+        pass
+
     async def resolve(self, connection_name: str) -> ConnectionName:
         return _parse_connection_name(connection_name)
 
@@ -43,11 +46,8 @@ class DnsResolver(dns.asyncresolver.Resolver):
     TXT records in DNS.
     """
 
-    def __init__(self, *args: Any, **kwargs: Any) -> None:
+    def __init__(self, *args: Any, client: Optional[Any] = None, **kwargs: Any) -> None:
         super().__init__(*args, **kwargs)
-        self._client: Any = None
-
-    def set_client(self, client: Any) -> None:
         self._client = client
 
     async def resolve(self, dns: str) -> ConnectionName:  # type: ignore

tests/unit/test_resolver.py

@@ -183,8 +183,7 @@ async def test_DnsResolver_with_direct_psc_dns_name() -> None:
         "connectionName": "my-project:europe-north2:my-instance"
     }
 
-    resolver = DnsResolver()
-    resolver.set_client(mock_client)
+    resolver = DnsResolver(client=mock_client)
 
     result = await resolver.resolve(dns_name)
 
@@ -208,8 +207,7 @@ async def test_DnsResolver_with_cname_resolving_to_psc_dns_name() -> None:
         "connectionName": "my-project:europe-north2:my-instance"
     }
 
-    resolver = DnsResolver()
-    resolver.set_client(mock_client)
+    resolver = DnsResolver(client=mock_client)
 
     # Patch resolver CNAME and TXT methods
     with patch.object(
@@ -240,8 +238,7 @@ async def test_DnsResolver_with_recursive_cnames_to_psc_dns_name() -> None:
         "connectionName": "my-project:europe-north2:my-instance"
     }
 
-    resolver = DnsResolver()
-    resolver.set_client(mock_client)
+    resolver = DnsResolver(client=mock_client)
 
     # Mock Lookup CNAME sequence
     cname_mock = AsyncMock(
@@ -285,8 +282,7 @@ async def test_DnsResolver_global_region_skips_direct_resolution() -> None:
     dns_name = "0123456789ab.fedcba9876543.global.sql-psc.goog"
 
     mock_client = AsyncMock()
-    resolver = DnsResolver()
-    resolver.set_client(mock_client)
+    resolver = DnsResolver(client=mock_client)
 
     # Patch CNAME and TXT to fail, so it eventually raises DnsResolutionError
     with patch.object(