InvalidRequestError: Class does not have a __table__ or __tablename__ specified and does not inherit from an existing table-mapped class.

[MichaelPereira]

Hi,

First of all congrats on the new release! This will allow us to go back to a pinned version of flask-sqlalchemy instead of the master branch 👍

On the other hand, the change #467 now generates this stack-trace in the Flask-AppBuilder project which I would need some help investigating to be able to use release 2.2 directly:

12:48:03   File "/src/<module_name>/models.py", line 10, in <module>
12:48:03     from flask_appbuilder.security.sqla.models import User
12:48:03   File "/usr/local/lib/python2.7/dist-packages/flask_appbuilder/security/sqla/models.py", line 12, in <module>
12:48:03     class Permission(Model):
12:48:03   File "/usr/local/lib/python2.7/dist-packages/flask_sqlalchemy/__init__.py", line 602, in __init__
12:48:03     DeclarativeMeta.__init__(self, name, bases, d)
12:48:03   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/ext/declarative/api.py", line 55, in __init__
12:48:03     _as_declarative(cls, classname, cls.__dict__)
12:48:03   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/ext/declarative/base.py", line 88, in _as_declarative
12:48:03     _MapperConfig.setup_mapping(cls, classname, dict_)
12:48:03   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/ext/declarative/base.py", line 103, in setup_mapping
12:48:03     cfg_cls(cls_, classname, dict_)
12:48:03   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/ext/declarative/base.py", line 133, in __init__
12:48:03     self._setup_inheritance()
12:48:03   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/ext/declarative/base.py", line 429, in _setup_inheritance
12:48:03     "table-mapped class." % cls
12:48:03 InvalidRequestError: Class <class 'flask_appbuilder.security.sqla.models.Permission'> does not have a __table__ or __tablename__ specified and does not inherit from an existing table-mapped class.

The error message contradicts the model declaration as it does have a __tablename defined:

class Permission(Model):
    __tablename__ = 'ab_permission'
    id = Column(Integer, Sequence('ab_permission_id_seq'), primary_key=True)
    name = Column(String(100), unique=True, nullable=False)

    def __repr__(self):
        return self.name

I understand that this change is related to the @declared_attr decorator but despite reading http://docs.sqlalchemy.org/en/latest/orm/extensions/declarative/api.html#api-reference I don't really know exactly how I should apply it to the model.

Thanks for your help

[davidism]

BoundDeclarativeMeta must be paired with a subclass of flask_sqlalchemy.Model. Is there a reason you're not using db.Model? If nothing else, your base model needs to inherit from flask_sqlalchemy.Model.

[dusktreader]

@davidism This does seem to be an issue. Using a tablename declared_attr from a 'mixin' does not work:

    def test_tablename_mixin(self):
        app = flask.Flask(__name__)
        db = fsa.SQLAlchemy(app)

        class Duck(db.Model):
            __abstract__ = True

        class NameMixin():

            @declared_attr
            def __tablename__(cls):
                return 'drake_mallard'

        class Darkwing(Duck, NameMixin):
            id = db.Column(db.Integer, primary_key=True)

        class Donald(Duck):
            id = db.Column(db.Integer, primary_key=True)

        self.assertEqual(Darkwing.__tablename__, 'drake_mallard')
        self.assertEqual(Donald.__tablename__, 'donald')

Results in the following test failure:

======================================================================
FAIL: test_tablename_mixin (__main__.TablenameTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test_sqlalchemy.py", line 359, in test_tablename_mixin
    self.assertEqual(Darkwing.__tablename__, 'drake_mallard')
AssertionError: 'darkwing' != 'drake_mallard'
- darkwing
+ drake_mallard

I do notice in the execution the following error is spawned:

sqlalchemy/ext/declarative/api.py:182: SAWarning: Unmanaged access of declarative attribute __tablename__ from non-mapped class Base
  (desc.fget.__name__, cls.__name__))

Perhaps I'm using my name mixin wrong?

[dusktreader]

@davidism it also appears that the solution that I had previously used in my own project, monkey patching _should_set_tablename with a lambda that always returns false, does not work any more and renders the following error:

sqlalchemy.exc.InvalidRequestError: Class <class MyClass > does not have a __table__ or __tablename__ specified and does not inherit from an existing table-mapped class.
ERROR: could not load /some/path/test/conftest.py

[dusktreader]

@davidism @MichaelPereira
I think I might have found something. The ordering of the base classes is important (now). If you add your name-mixin class as the first base-class, the error goes away. For the test case I posted above, changing to:

    def test_tablename_mixin(self):
        app = flask.Flask(__name__)
        db = fsa.SQLAlchemy(app)

        class Duck(db.Model):
            __abstract__ = True

        class NameMixin():

            @declared_attr
            def __tablename__(cls):
                return 'drake_mallard'

        class Darkwing(NameMixin, Duck):
            id = db.Column(db.Integer, primary_key=True)

        class Donald(Duck):
            id = db.Column(db.Integer, primary_key=True)

        self.assertEqual(Darkwing.__tablename__, 'drake_mallard')
        self.assertEqual(Donald.__tablename__, 'donald')

eliminates the problem. This isn't a desirable solution, however.

[davidism]

The order of base classes has always been significant in Python, bases are scanned left to right. So I'm not going to consider that part a bug.

__tablename__ being ignored in mixins is a bug and is already reported in #470.

I'm fairly sure this issue has to do with their use of a completely separate Model.

[davidism]

@MichaelPereira did you have a chance to try out my initial suggestion? I'd like to know if this is actually a bug so I can work on 2.2.1 over the weekend.

[ThiefMaster]

I'm quite sure it is a bug, it also fails in my application in this model - and no mixins are involved there: https://github.com/indico/indico/blob/master/indico/modules/events/registration/models/items.py

[davidism]

I'm going to need a minimal example. These projects are nice but it's hard to trace what's going on. Just to confirm, you're saying this is a different bug, not a duplicate of the other __tablename__ issues? From my initial look at this bug, the op is using a completely independent base model that does not have the expected interface.

Their base model class should look like

from flask_sqlalchemy import Model as _BaseModel

# no as_declarative here, that's what make_declarative_base does
# or make_declarative_base should be overridden to return the as_declarative version
class Model(_BaseModel):
    ...

[MichaelPereira]

@davidism thanks for looking into the problem. I'm sorry for not getting back earlier as we got swamped with the S3 outage in the meantime. I will try to get a reproducible example out of it since our tool is not open-source to help the resolution of the bug.

[davidism]

@MichaelPereira oh, I was under the impression that your project was Flask-AppBuilder, since you linked to its source. The issue appears to be there, although an example is still useful.

[MichaelPereira]

I contributed a little to it, but our project builds upon it. Anyway, if it's fixed for Flask-AppBuilder, it will be fixed for everyone using it :)

It took me a few hours but I was able to get a reproducible error with just the bare minimum. Here are the steps:

• clone https://github.com/MichaelPereira/Flask-AppBuilder.git
• create a docker image from that repo: docker build -t . Note the docker container id at the end
• go to the registration_user example folder: cd examples/user_registration/
• run the docker image with that example: docker run -v $(pwd):/app <container_id> python /app/run.py
  You should get the following stack-trace:

$ docker run -v `pwd`:/app 1741cdc3a399  python /app/run.py
/usr/local/lib/python3.5/site-packages/flask_sqlalchemy/__init__.py:839: FSADeprecationWarning: SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and will be disabled by default in the future.  Set it to True or False to suppress this warning.
  'SQLALCHEMY_TRACK_MODIFICATIONS adds significant overhead and '
Traceback (most recent call last):
  File "/app/run.py", line 1, in <module>
    from app import app
  File "/app/app/__init__.py", line 16, in <module>
    appbuilder = AppBuilder(app, db.session)
  File "/usr/local/lib/python3.5/site-packages/flask_appbuilder/base.py", line 130, in __init__
    self.init_app(app, session)
  File "/usr/local/lib/python3.5/site-packages/flask_appbuilder/base.py", line 147, in init_app
    from flask_appbuilder.security.sqla.manager import SecurityManager
  File "/usr/local/lib/python3.5/site-packages/flask_appbuilder/security/sqla/manager.py", line 7, in <module>
    from .models import User, Permission, PermissionView, RegisterUser, ViewMenu, Role
  File "/usr/local/lib/python3.5/site-packages/flask_appbuilder/security/sqla/models.py", line 12, in <module>
    class Permission(Model):
  File "/usr/local/lib/python3.5/site-packages/flask_sqlalchemy/__init__.py", line 602, in __init__
    DeclarativeMeta.__init__(self, name, bases, d)
  File "/usr/local/lib/python3.5/site-packages/sqlalchemy/ext/declarative/api.py", line 64, in __init__
    _as_declarative(cls, classname, cls.__dict__)
  File "/usr/local/lib/python3.5/site-packages/sqlalchemy/ext/declarative/base.py", line 88, in _as_declarative
    _MapperConfig.setup_mapping(cls, classname, dict_)
  File "/usr/local/lib/python3.5/site-packages/sqlalchemy/ext/declarative/base.py", line 103, in setup_mapping
    cfg_cls(cls_, classname, dict_)
  File "/usr/local/lib/python3.5/site-packages/sqlalchemy/ext/declarative/base.py", line 133, in __init__
    self._setup_inheritance()
  File "/usr/local/lib/python3.5/site-packages/sqlalchemy/ext/declarative/base.py", line 430, in _setup_inheritance
    "table-mapped class." % cls
sqlalchemy.exc.InvalidRequestError: Class <class 'flask_appbuilder.security.sqla.models.Permission'> does not have a __table__ or __tablename__ specified and does not inherit from an existing table-mapped class.

About the make_declarative reference, I don't have enough knowledge to properly understand what it is doing but I know that Flask-AppBuilder defines it this way https://github.com/dpgaspar/Flask-AppBuilder/blob/master/flask_appbuilder/models/sqla/__init__.py#L23-L39

We had an issue with the number of argument, so we had to change it this same way in our project too: https://github.com/MichaelPereira/Flask-AppBuilder/pull/1/files#diff-d35cb966075d5560db04866a27e50fc8

Thanks again for your help and please let me know if I can be of more help

[davidism]

Closing this as it seems to be an issue with Flask-AppBuilder, not directly related to the tablename issue. Check #541.