feat: Add key to engine constructor (#156)

* feat: feat: Add `key` to engine constructor * add column test for tc

Author: duwenxin99

src/langchain_google_cloud_sql_pg/engine.py

@@ -91,13 +91,19 @@ class PostgresEngine:
  """A class for managing connections to a Cloud SQL for Postgres database."""
 
  _connector: Optional[Connector] = None
+ __create_key = object()
 
  def __init__(
  self,
+ key: object,
  engine: AsyncEngine,
  loop: Optional[asyncio.AbstractEventLoop],
  thread: Optional[Thread],
  ):
+ if key != PostgresEngine.__create_key:
+ raise Exception(
+ "Only create class through 'create' or 'create_sync' methods!"
+ )
  self._engine = engine
  self._loop = loop
  self._thread = thread
@@ -191,7 +197,7 @@ async def getconn() -> asyncpg.Connection:
  "postgresql+asyncpg://",
  async_creator=getconn,
  )
- return cls(engine, loop, thread)
+ return cls(cls.__create_key, engine, loop, thread)
 
  @classmethod
  async def afrom_instance(
@@ -218,7 +224,7 @@ async def afrom_instance(
 
  @classmethod
  def from_engine(cls, engine: AsyncEngine) -> PostgresEngine:
- return cls(engine, None, None)
+ return cls(cls.__create_key, engine, None, None)
 
  async def _aexecute(self, query: str, params: Optional[dict] = None):
  """Execute a SQL query."""

tests/test_postgresql_engine.py

@@ -173,6 +173,8 @@ async def getconn() -> asyncpg.Connection:
  async def test_column(self, engine):
  with pytest.raises(ValueError):
  Column("test", VARCHAR)
+ with pytest.raises(ValueError):
+ Column(1, "INTEGER")
 
 
 @pytest.mark.asyncio
@@ -275,3 +277,11 @@ async def test_password(
  assert engine
  engine._execute("SELECT 1")
  PostgresEngine._connector = None
+
+ async def test_engine_constructor_key(
+ self,
+ engine,
+ ):
+ key = object()
+ with pytest.raises(Exception):
+ PostgresEngine(key, engine)