feat: add create_table parameter to control automatic table creation (#10)

Author: hsluoyz

README.md

@@ -67,6 +67,27 @@ adapter = sqlalchemy_adapter.Adapter('sqlite:///test.db', table_name=custom_tabl
 e = casbin.Enforcer('path/to/model.conf', adapter)
 ```
 
+## Prevent Automatic Table Creation
+
+By default, the adapter automatically creates the necessary database tables during initialization. If you want to use the adapter only as an intermediary without automatically creating tables, you can set the `create_table` parameter to `False`:
+
+```python
+import sqlalchemy_adapter
+import casbin
+
+# Create adapter without automatically creating tables
+adapter = sqlalchemy_adapter.Adapter('sqlite:///test.db', create_table=False)
+
+e = casbin.Enforcer('path/to/model.conf', adapter)
+```
+
+This is useful when:
+- Tables are already created by your database migration system
+- You want to manage table creation separately
+- You are using the adapter as an intermediary between SQLAlchemy and your system
+
+**Note:** When `create_table=False`, you are responsible for ensuring the required tables exist in the database before using the adapter.
+
 
 ### Getting Help
 

sqlalchemy_adapter/adapter.py

@@ -80,6 +80,7 @@ def __init__(
         db_class=None,
         table_name="casbin_rule",
         filtered=False,
+        create_table=True,
     ):
         if isinstance(engine, str):
             self._engine = create_engine(engine)
@@ -107,7 +108,8 @@ def __init__(
         self._db_class = db_class
         self.session_local = sessionmaker(bind=self._engine)
 
-        metadata.create_all(self._engine)
+        if create_table:
+            metadata.create_all(self._engine)
         self._filtered = filtered
 
     @contextmanager

tests/test_adapter.py

@@ -409,3 +409,78 @@ def test_update_filtered_policies(self):
 
         e.update_filtered_policies([["bob", "data2", "read"]], 0, "bob")
         self.assertTrue(e.enforce("bob", "data2", "read"))
+
+    def test_create_table_false(self):
+        """Test that tables are not created when create_table=False"""
+        from sqlalchemy import inspect
+
+        engine = create_engine("sqlite://")
+
+        # Create adapter with create_table=False
+        adapter = Adapter(engine, create_table=False)
+
+        # Verify that the table was NOT created
+        inspector = inspect(engine)
+        tables = inspector.get_table_names()
+        self.assertEqual(
+            len(tables), 0, "No tables should be created when create_table=False"
+        )
+
+    def test_create_table_true_default(self):
+        """Test that tables are created by default (backward compatibility)"""
+        from sqlalchemy import inspect
+
+        engine = create_engine("sqlite://")
+
+        # Create adapter without specifying create_table (should default to True)
+        adapter = Adapter(engine)
+
+        # Verify that the table WAS created
+        inspector = inspect(engine)
+        tables = inspector.get_table_names()
+        self.assertIn("casbin_rule", tables, "Table should be created by default")
+
+    def test_create_table_custom_table_name(self):
+        """Test that custom table name is not created when create_table=False"""
+        from sqlalchemy import inspect
+
+        engine = create_engine("sqlite://")
+        table_name = "my_custom_table"
+
+        # Create adapter with custom table name and create_table=False
+        adapter = Adapter(engine, table_name=table_name, create_table=False)
+
+        # Verify that the table was NOT created
+        inspector = inspect(engine)
+        tables = inspector.get_table_names()
+        self.assertEqual(
+            len(tables), 0, "No tables should be created when create_table=False"
+        )
+
+    def test_create_table_custom_db_class(self):
+        """Test that custom db_class table is not created when create_table=False"""
+        from sqlalchemy import inspect
+
+        class CustomRule(Base):
+            __tablename__ = "custom_rule_table"
+
+            id = Column(Integer, primary_key=True)
+            ptype = Column(String(255))
+            v0 = Column(String(255))
+            v1 = Column(String(255))
+            v2 = Column(String(255))
+            v3 = Column(String(255))
+            v4 = Column(String(255))
+            v5 = Column(String(255))
+
+        engine = create_engine("sqlite://")
+
+        # Create adapter with custom db_class and create_table=False
+        adapter = Adapter(engine, db_class=CustomRule, create_table=False)
+
+        # Verify that the table was NOT created
+        inspector = inspect(engine)
+        tables = inspector.get_table_names()
+        self.assertEqual(
+            len(tables), 0, "No tables should be created when create_table=False"
+        )