Better handling of "two-way" nesting about marshmallow

[gdiscry]

I'm interested in this feature.

Personally, the infinite recursion problem is not an issue for my use case if we could also use hierarchical only/exclude parameters which would look like:

serialized = BookMarshal(book, only=('isbn', 'date_created', 'author.created'))

or

serialized = BookMarshal(book, exclude=('author.books',))

I use marshmallow when generating CSV files from SQLAlchemy objects with csv.DictWriter. I serialize the SQLAlchemy object with marshmallow, flatten the resulting dict (keys are joined with .) and pass that dict to csv.DictWriter. As DictWriter already requires a list of fieldnames, using the same list with the serializer would be great.

Anyway, that's another feature. The conclusion is that explicit is better than implicit.

[DeaconDesperado]

👍 for proposed API, even though it's a big change. The resolution by string name is a pretty common pattern for situations like this, where it's important to make definition order have no effect on lookup.

[sloria]

@gdiscry I like the explicitness of your proposed hierarchical filtering.

I'm leaning towards going ahead with this. Will likely starting prototyping it for the next release.

[justanr]

I'm going to say that this is a big thumbs up, as well. If you're doubting on if they should be passed as strings or not, you could take a page from SQLAlchemy's book and allow a callable (such as a lambda) instead.

[DigTheDoug]

Glad to hear it, this is definitely a plus in my book. Using mongodb we use ReferenceFields often and being able to match that pattern when we serialize them would be great.

[sloria]

This has been implemented on develop. Feel free to try it out and give feedback.

pip install -U git+https://github.com/sloria/marshmallow.git@dev