refactor: Make SQLSink a generic with a SQLConnector type parameter

samples/sample_target_sqlite/__init__.py

@@ -26,7 +26,7 @@ def get_sqlalchemy_url(self, config: dict[str, t.Any]) -> str:  # noqa: PLR6301
         return f"sqlite:///{config[DB_PATH_CONFIG]}"
 
 
-class SQLiteSink(SQLSink):
+class SQLiteSink(SQLSink[SQLiteConnector]):
     """The Sink class for SQLite.
 
     This class allows developers to optionally override `get_records()` and other

singer_sdk/sinks/sql.py

@@ -23,11 +23,13 @@
 
     from singer_sdk.target_base import Target
 
+_C = t.TypeVar("_C", bound=SQLConnector)
 
-class SQLSink(BatchSink):
+
+class SQLSink(BatchSink, t.Generic[_C]):
     """SQL-type sink type."""
 
-    connector_class: type[SQLConnector]
+    connector_class: type[_C]
     soft_delete_column_name = "_sdc_deleted_at"
     version_column_name = "_sdc_table_version"
 
@@ -37,7 +39,7 @@ def __init__(
         stream_name: str,
         schema: dict,
         key_properties: t.Sequence[str] | None,
-        connector: SQLConnector | None = None,
+        connector: _C | None = None,
     ) -> None:
         """Initialize SQL Sink.
 
@@ -48,12 +50,12 @@ def __init__(
             key_properties: The primary key columns.
             connector: Optional connector to reuse.
         """
-        self._connector: SQLConnector
+        self._connector: _C
         self._connector = connector or self.connector_class(dict(target.config))
         super().__init__(target, stream_name, schema, key_properties)
 
     @property
-    def connector(self) -> SQLConnector:
+    def connector(self) -> _C:
         """The connector object.
 
         Returns:

tests/conftest.py

@@ -138,7 +138,7 @@ class SQLConnectorMock(SQLConnector):
     """A Mock SQLConnector class."""
 
 
-class SQLSinkMock(SQLSink):
+class SQLSinkMock(SQLSink[SQLConnectorMock]):
     """A mock Sink class."""
 
     name = "sql-sink-mock"