Initalizing file_upload with subclassed SQLAlchemy instance?

[GhastlyParadox]

Hi Joe,

First, thank you for developing this. Provided I can get it working in my project, it'd be perfect for my needs. I'm working on an image manager feature for an existing Flask application with a rather large/complex MySQL database setup that serves as a REST API. While the database itself is a beast, for this project I'm really only dealing with a single table that has no relationships.

The database had been set up using raw SQLAlchemy, but I reconfigured it using Flask-SQLAlchemy, in hopes to get it working with flask-file-upload. So far though, I'm having trouble initializing it, getting the following error:

Traceback (most recent call last): File "/Users/aglane/Box Sync/Git/flora-DEV/herbflask/__init__.py", line 1, in <module> from application import create_app File "/Users/aglane/Box Sync/Git/flora-DEV/herbflask/application/__init__.py", line 32, in <module> from .db.miflora import MIFloraDB File "/Users/aglane/Box Sync/Git/flora-DEV/herbflask/application/db/miflora.py", line 1113, in <module> class ImagesDev(MIFLORA_BASE): File "/Users/aglane/Box Sync/Git/flora-DEV/env/lib/python3.7/site-packages/flask_file_upload/model.py", line 50, in __new__ new_cols_list, filenames_list = _ModelUtils.get_attr_from_model(instance, new_cols, filenames, db) File "/Users/aglane/Box Sync/Git/flora-DEV/env/lib/python3.7/site-packages/flask_file_upload/_model_utils.py", line 123, in get_attr_from_model new_cols.append(_ModelUtils.columns_dict(attr, db)) File "/Users/aglane/Box Sync/Git/flora-DEV/env/lib/python3.7/site-packages/flask_file_upload/_model_utils.py", line 90, in columns_dict create_col File "/Users/aglane/Box Sync/Git/flora-DEV/env/lib/python3.7/site-packages/flask_file_upload/_model_utils.py", line 36, in create_keys col_dict[key] = fn(key, key) File "/Users/aglane/Box Sync/Git/flora-DEV/env/lib/python3.7/site-packages/flask_file_upload/_model_utils.py", line 86, in create_col return db.Column(db.String(str_len), key=key, name=name) AttributeError: 'NoneType' object has no attribute 'Column'

It seems as though the database isn't being recognized as an SQLAlchemy instance?

I'm wondering whether this may be because I've subclassed the SQLAlchemy instance with a MIFloraDB class, which handles all the query logic for the REST API - e.g.

from flask_sqlalchemy import SQLAlchemy

class MIFloraDB(SQLAlchemy):
...

Which I then import into my application (app factory) to create the SQLAlchemy instance:

flora_db = MIFloraDB()

def create_app():

with app.app_context():

flora_db.init_app(app)

file_upload.init_app(app, flora_db)

return app

Everything else seems to be configured properly, so that's my best guess at this point, but any thoughts/suggestions very much appreciated!

[GhastlyParadox]

I managed to get it running by simply adding a constructor with a super function for inheritance - e.g.

class MIFloraDB(SQLAlchemy):
def __init__(self):
super(MIFloraDB, self).__init__()

Now to dive in and start working with it. Thanks again.

[GhastlyParadox]

Ugh, spoke too soon - forgot I'd commented out the file_upload.Model decorator. Still getting the same error.

[joegasewicz]

@GhastlyParadox Hi
Thanks for the message, i'm currently at work but as soon as I get off i'll look into this issue for you and get a fix out asap.
Thank you
Joe

[GhastlyParadox]

Hi Joe, just getting back to work after a long weekend, and saw you replied. Many thanks!

[joegasewicz]

Hi @GhastlyParadox , it looks like the db is not initiated. The problem is that Flask-Sqlalchemy calls to a __get__ descriptor which initiates the SqlAlchemy session object. So we have to delay this call. If you're not using Flask-Sqlalchemy then this library currently will not be able to create a session. If this is the case, then keep this issue open & i can provide the fix for this.

To confirm this, can you run this please:

print(db.__dict__)

And post the output here, thank you

[GhastlyParadox]

Hi Joe,

I am using Flask-Sqlalchemy now, but my models are currently set up using a raw declarative_base - e.g.MIFLORA_BASE = declarative_base()

But the db instance itself is Flask-Sqlalchemy. I actually wondered whether I needed to be using Flask-Sqlalchemy db.Model as well, for the full Flask-Sqlalchemy configuration, in order to get this working. So I tried that -- it took some restructuring to avoid circular imports -- but in the end, once I got everything working with db.Model, I got the same result/error. So I went back to just using declarative_base(), as it's a cleaner set up.

That said, my current db.__dict__ output is pasted below. Thanks so much for looking into this!

2020-08-12 14:35:30,940 - application - INFO - {'use_native_unicode': True, 'Query': <class 'flask_sqlalchemy.BaseQuery'>, 'session': <sqlalchemy.orm.scoping.scoped_session object at 0x10691da90>, 'Model': <class 'sqlalchemy.ext.declarative.api.Model'>, '_engine_lock': <unlocked _thread.lock object at 0x10690ed20>, 'app': None, '_engine_options': {}, 'ARRAY': <class 'sqlalchemy.sql.sqltypes.ARRAY'>, 'BIGINT': <class 'sqlalchemy.sql.sqltypes.BIGINT'>, 'BINARY': <class 'sqlalchemy.sql.sqltypes.BINARY'>, 'BLANK_SCHEMA': symbol('blank_schema'), 'BLOB': <class 'sqlalchemy.sql.sqltypes.BLOB'>, 'BOOLEAN': <class 'sqlalchemy.sql.sqltypes.BOOLEAN'>, 'BigInteger': <class 'sqlalchemy.sql.sqltypes.BigInteger'>, 'Binary': <class 'sqlalchemy.sql.sqltypes.Binary'>, 'Boolean': <class 'sqlalchemy.sql.sqltypes.Boolean'>, 'CHAR': <class 'sqlalchemy.sql.sqltypes.CHAR'>, 'CLOB': <class 'sqlalchemy.sql.sqltypes.CLOB'>, 'CheckConstraint': <class 'sqlalchemy.sql.schema.CheckConstraint'>, 'Column': <class 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[joegasewicz]

Sorry for the delay @GhastlyParadox i'm going to pick this issue up today...

[joegasewicz]

@GhastlyParadox

But the db instance itself is Flask-Sqlalchemy. I actually wondered whether I needed to be using Flask-Sqlalchemy db.Model

Yes, you must pass db.Model to any class that is decorated with @file_upload.Model.

I'm going to provide details and any required fixes to port FFU to be able to work with vanilla SqlAlchemy as well. This issue will be related to this new feature so please keep this open until the fix & or documentation is updated... ill pick this up tomorrow morning, thanks.
Joe

[joegasewicz]

this is being fixed in #99