Assertion "schema is not None"

Hello: I'm following the simple example from the project's front page: https://pypi.org/project/Flask-SQLAlchemy/ but with a mariadb database. ``` from flask import Flask from flask_sqlalchemy import SQLAlchemy from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column app = Flask(__name__) app.config["SQLALCHEMY_DATABASE_URI"] = "mariadb+pymysql://root:test_password_1234@localhost:3306" class Base(DeclarativeBase): pass db = SQLAlchemy(app, model_class=Base) class User(db.Model): id: Mapped[int] = mapped_column(db.Integer, primary_key=True) username: Mapped[str] = mapped_column(db.String, unique=True, nullable=False) with app.app_context(): db.create_all() db.session.add(User(username="example")) db.session.commit() users = db.session.execute(db.select(User)).scalars() ``` I get an AssertionError ``` --------------------------------------------------------------------------- AssertionError Traceback (most recent call last) Cell In[2], line 10 8 username: Mapped[str] = mapped_column(db.String, unique=True, nullable=False) 9 with app.app_context(): ---> 10 db.create_all() 12 db.session.add(User(username="example")) 13 db.session.commit() File ~/p/Sketches/python/flask/venv/lib/python3.13/site-packages/flask_sqlalchemy/extension.py:900, in SQLAlchemy.create_all(self, bind_key) 883 def create_all(self, bind_key: str | None | list[str | None] = "__all__") -> None: 884 """Create tables that do not exist in the database by calling 885 ``metadata.create_all()`` for all or some bind keys. This does not 886 update existing tables, use a migration library for that. (...) 898 Added the ``bind`` and ``app`` parameters. 899 """ --> 900 self._call_for_binds(bind_key, "create_all") File ~/p/Sketches/python/flask/venv/lib/python3.13/site-packages/flask_sqlalchemy/extension.py:881, in SQLAlchemy._call_for_binds(self, bind_key, op_name) 878 raise sa_exc.UnboundExecutionError(message) from None 880 metadata = self.metadatas[key] --> 881 getattr(metadata, op_name)(bind=engine) File ~/p/Sketches/python/flask/venv/lib/python3.13/site-packages/sqlalchemy/sql/schema.py:5925, in MetaData.create_all(self, bind, tables, checkfirst) 5901 def create_all( 5902 self, 5903 bind: _CreateDropBind, 5904 tables: Optional[_typing_Sequence[Table]] = None, 5905 checkfirst: bool = True, 5906 ) -> None: 5907 """Create all tables stored in this metadata. 5908 5909 Conditional by default, will not attempt to recreate tables already (...) 5923 5924 """ -> 5925 bind._run_ddl_visitor( 5926 ddl.SchemaGenerator, self, checkfirst=checkfirst, tables=tables 5927 ) File ~/p/Sketches/python/flask/venv/lib/python3.13/site-packages/sqlalchemy/engine/base.py:3249, in Engine._run_ddl_visitor(self, visitorcallable, element, **kwargs) 3242 def _run_ddl_visitor( 3243 self, 3244 visitorcallable: Type[Union[SchemaGenerator, SchemaDropper]], 3245 element: SchemaItem, 3246 **kwargs: Any, 3247 ) -> None: 3248 with self.begin() as conn: -> 3249 conn._run_ddl_visitor(visitorcallable, element, **kwargs) File ~/p/Sketches/python/flask/venv/lib/python3.13/site-packages/sqlalchemy/engine/base.py:2456, in Connection._run_ddl_visitor(self, visitorcallable, element, **kwargs) 2444 def _run_ddl_visitor( 2445 self, 2446 visitorcallable: Type[Union[SchemaGenerator, SchemaDropper]], 2447 element: SchemaItem, 2448 **kwargs: Any, 2449 ) -> None: 2450 """run a DDL visitor. 2451 2452 This method is only here so that the MockConnection can change the 2453 options given to the visitor so that "checkfirst" is skipped. 2454 2455 """ -> 2456 visitorcallable(self.dialect, self, **kwargs).traverse_single(element) File ~/p/Sketches/python/flask/venv/lib/python3.13/site-packages/sqlalchemy/sql/visitors.py:664, in ExternalTraversal.traverse_single(self, obj, **kw) 662 meth = getattr(v, "visit_%s" % obj.__visit_name__, None) 663 if meth: --> 664 return meth(obj, **kw) File ~/p/Sketches/python/flask/venv/lib/python3.13/site-packages/sqlalchemy/sql/ddl.py:960, in SchemaGenerator.visit_metadata(self, metadata) 956 else: 957 tables = list(metadata.tables.values()) 959 collection = sort_tables_and_constraints( --> 960 [t for t in tables if self._can_create_table(t)] 961 ) 963 seq_coll = [ 964 s 965 for s in metadata._sequences.values() 966 if s.column is None and self._can_create_sequence(s) 967 ] 969 event_collection = [t for (t, fks) in collection if t is not None] File ~/p/Sketches/python/flask/venv/lib/python3.13/site-packages/sqlalchemy/sql/ddl.py:925, in SchemaGenerator._can_create_table(self, table) 923 if effective_schema: 924 self.dialect.validate_identifier(effective_schema) --> 925 return not self.checkfirst or not self.dialect.has_table( 926 self.connection, table.name, schema=effective_schema 927 ) File <string>:2, in has_table(self, connection, table_name, schema, **kw) File ~/p/Sketches/python/flask/venv/lib/python3.13/site-packages/sqlalchemy/engine/reflection.py:89, in cache(fn, self, con, *args, **kw) 87 info_cache = kw.get("info_cache", None) 88 if info_cache is None: ---> 89 return fn(self, con, *args, **kw) 90 exclude = {"info_cache", "unreflectable"} 91 key = ( 92 fn.__name__, 93 tuple( (...) 102 ), 103 ) File ~/p/Sketches/python/flask/venv/lib/python3.13/site-packages/sqlalchemy/dialects/mysql/base.py:2834, in MySQLDialect.has_table(self, connection, table_name, schema, **kw) 2831 if schema is None: 2832 schema = self.default_schema_name -> 2834 assert schema is not None 2836 full_name = ".".join( 2837 self.identifier_preparer._quote_free_identifiers( 2838 schema, table_name 2839 ) 2840 ) 2842 # DESCRIBE *must* be used because there is no information schema 2843 # table that returns information on temp tables that is consistently 2844 # available on MariaDB / MySQL / engine-agnostic etc. 2845 # therefore we have no choice but to use DESCRIBE and an error catch 2846 # to detect "False". See issue #9058 AssertionError: ``` Environment: - Python version: 3.13 - Flask-SQLAlchemy version: - SQLAlchemy version: ``` > pip freeze blinker==1.9.0 click==8.1.8 Flask==3.1.0 Flask-SQLAlchemy==3.1.1 greenlet==3.1.1 itsdangerous==2.2.0 Jinja2==3.1.6 MarkupSafe==3.0.2 PyMySQL==1.1.1 SQLAlchemy==2.0.40 typing_extensions==4.13.1 Werkzeug==3.1.3 ```