Support SQLAlchemy models with hybrid properties

[omrihar]

Is your feature request related to a problem? Please describe.
I would like to be able to return an SQLAlchemy model and have it cast to a Pydantic schema. The problem is that hybrid properties on SQLAlchemy do not appear in the __dict__ variable of the model and therefore do not appear in the vars() function.

Describe the solution you'd like
I would like json_encodable to support SQLAlchemy models with hybrid properties. It is possible to use the inspection function of SQLAlchemy to achieve this:

from sqlalchemy import inspect
...
insp = inspect(Item)
for field in insp.mapper.orm_all_descriptors:
   ...

however I'm not sure how to extract the field name from this procedure.

Describe alternatives you've considered
A different alternative, which @tiangolo mentioned, is to try to obtain the property by name bsed on the pydantic model. This will also work, if we use getattr. For example, if I have an Item instance called item with a hybrid property title, it's possible to get it by item.title or getattr(item, 'title'), but not by using item['title'] or item.get('title').

Additional context
I'm using sqlalchemy_utils to provide translations-aware models. This only works on PostgreSQL. The field in the table is called, for example title_tr which is a JSONB field that has keys as language names and as values the translations. Then the sqlalchemy_utils.TranslationHybrid is a property on the instance that takes the value of the title_tr['current_locale'].
See https://sqlalchemy-utils.readthedocs.io/en/latest/internationalization.html.

[tiangolo]

@omrihar I'm working on improving the way we handle this in a PR to Pydantic here: pydantic/pydantic#520

This would help to solve this, even for nested relationship/models, lists of results, etc.

[tiangolo]

FastAPI now has a deep integration with the new Pydantic ORM mode.

This includes support for hybrid properties, lazy-loading, and many other things.

Check the new docs here: https://fastapi.tiangolo.com/tutorial/sql-databases/

[omrihar]

Hi @tiangolo , great work! I read through the very thorough docs and I really like it :) And orm_mode as well :) I guess this issue can be closed now... I'm thinking of refactoring my app (based on the fullstack cookiecutter) to reflect the changes.

[tiangolo]

Great! Thanks for reporting back and closing the issue.

Just so you know, the cookiecutter is not updated yet with these new changes.