Enable Deserialization of Many-to-One Nested Objects that DNE in DB

[seanharr11]

Proposition: Given 'One' object composed of nested fields, with each
nested field containing 'Many' objects, on deserialization instantiate
each nested object into an instance of the nested field's SQLAlchemy
Model if it does not already exist in the DB.

Current behavior is to fail ungracefully & non-verbosely if a nested
object DNE in DB. The "NoResultFound" exception is raised by
"Query.one()".

A sample problem-case is as follows:

i.) A POST request is sent to a server, and contains a JSON object which contains both parent, and children which do not yet exist on the DB.

author_dict = {'name': 'Robert Jordan', books: 
                             [{'title': 'The Eye of the World'}, 
                              {'title': 'A Memory of Light'}]}

ii.) This object is deserialized with a (required) session object, and because the 2 books (in the collection of 'books' above) do not yet exist in the DB, an exception gets thrown when they are retrieved.

author_obj = author_schema.load(author_dict, session).data

Without the 'books', the author object can be deserialized even though it has not yet been created on the DB. The proposed feature would keep this consistent across many-to-one nested objects.

[sloria]

This seems like a good change. There will certainly be use cases where the code should error if related objects are not in the database. In though cases, though, the user could use a validator.

@jmcarp Thoughts on this?

[sloria]

Let's move this forward. @seanharr11 Could you please add tests for this behavior?

[seanharr11]

Yeah I can add tests. Will hopefully get this wrapped up this week.

On Sunday, June 12, 2016, Steven Loria notifications@github.com wrote:

Let's move this forward. @seanharr11 https://github.com/seanharr11
Could you please add tests for this behavior?

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[sloria]

Thanks @seanharr11 .

[seanharr11]

Tests are now added, verified, and pushed to branch. @sloria

[sloria]

Thanks!