How to structure a real world application

Hi,

I believe that due to recent updates in both apispec and marshmallow my application started to throw warnings and exceptions (e.g., marshmallow.exceptions.RegistryError, apispec.exceptions.DuplicateComponentNameError) that were not happening a few weeks ago.

I couldn’t came up with a minimal example to illustrate this yet. But I wonder if you could provide an example (beyond the basic “Petstore example” from the docs) of how to structure a more realistic application (like using the application factory pattern, splitting schemas and views in different modules, etc).

Regards,

[svidela]

Hi again,

I wanted to share the 2 things I had to do in order to adapt my application to be compatible with flask-rest-api 0.13 ( actually, apispec>1.0.0b6, marshmallow>3.0.0rc3).

• Make sure to import all my schemas before calling init_app Otherwise, I’d get:

marshmallow.exceptions.RegistryError: Class with name ‘PetSchema’ was not found. You may need to import the class.

when using the Api.definition decorator with a schema having a nested field declared with a class name string like in two-way nesting in marshmallow schemas .

You can solve this either not using the Api.definition or making sure to import all your schemas before calling init_app.

• Don’t let apispec to register nested schemas automatically in the spec’s components Otherwise, I’d get either:

apispec.exceptions.DuplicateComponentNameError: Another schema with name “Pet” is already registered.

when using the Api.definition decorator, or

UserWarning: Multiple schemas resolved to the name Person. The name has been modified. Either manually add each of the schemas with a different name or provide a custom schema_name_resolver. UserWarning,

when the Api.definition decorator is not used at all but there are nested fields declared with modifiers (like only=('id', )).

In the first case (using the Api.definition decorator), the issue is that apispec is also registering schemas in the spec’s components using its default schema_name_resolver.

In the second case (not using the Api.definition and having nested fields with modifiers), apispec tries to register the same schema name for each modifiers combination used and shows the warning.

The workaround I found for this is to don’t let apispec to register nested schemas automatically and use the Api.definition decorator. For this I call init_app passing a custom marshmallow plugin:

from flask import Flask

from flask_rest_api import Api
from apispec.ext.marshmallow import MarshmallowPlugin

api = Api()

def create_app():
    app = Flask(__name__)
    
    ma_plugin = MarshmallowPlugin(schema_name_resolver=lambda _: False)
    api.init_app(app, spec_kwargs=dict(marshmallow_plugin=ma_plugin))
    
    return app

For a minimal example reproducing these two issues you may want to checkout flask-rest-api-example.

Regards,

[lafrech]

I’ve been working on a simple real-life example and I came up with a minimal application using sqlalchemy.

https://github.com/lafrech/flask-smorest-sqlalchemy-example

Not done (are such things ever done ?) but feedback welcome already.