Added sort support

[CaselIT]

Add support for sorting the return values of a SQLAlchemyConnectionField

The sort argument of SQLAlchemyConnectionField supports sorting over a single over multiple field.

In the utils file I've added

• the function sort_enum_for_model to create a graphene Enum with all be possible field and order combination for a particular sqlalchemy model as suggested by @Cito
• the function sort_argument_for_model to automacally create the enum and return the attribute to use in the connection field

The test and documentation are still missing, because first I wanted to get some feedback about the implementation.

Regarding the value of the sort enumerator at first I tried to set the values of the enum to the ascenting or descenting operators of sqlalchemy simplify the logic of the get_query but that results in an error when graphql builds the ast graph, so I reverted to use a list column_name, operator that is less than optimal since every time it needs to query the model to create the operators.

Thanks to @Cito to the input in #40
Closes #40

[coveralls]

Coverage decreased (-6.5%) to 84.424% when pulling b192e78 on CaselIT:sortable_field into 4827ce2 on graphql-python:master.

[coveralls]

Coverage decreased (-6.7%) to 84.308% when pulling d0337ba on CaselIT:sortable_field into 4827ce2 on graphql-python:master.

[CaselIT]

Regarding the value of the sort enumerator at first I tried to set the values of the enum to the ascenting or descenting operators of sqlalchemy simplify the logic of the get_query but that results in an error when graphql builds the ast graph, so I reverted to use a list column_name, operator that is less than optimal since every time it needs to query the model to create the operators.

I've changed the implementation to use a subclass of string instead of the list, so that the ast graph can be created successfully and there is no need to query the model every time.

[coveralls]

Coverage decreased (-6.7%) to 84.308% when pulling 2fd5203 on CaselIT:sortable_field into 4827ce2 on graphql-python:master.

[Cito]

Nice, thank you.

Maybe, as I've already commented in #40, the sort argument should be added by default to the SQLAlchemyConnectionField, so that you don't need to specify it manually. That would be similar to how a Graphene ConnectionField comes with first, last arguments by default, which also don't need to added manually.

[CaselIT]

Good idea. I'll add it.
Do you think it should have a default value when added by default?

[Cito]

For an SQLAlchemyConnectionField it probably makes sense to use the id as default value for the sort argument so that you always get a reproducable order.

[CaselIT]

SQLAlchemyConnectionField now adds the sort attribute by default, with a default sort over the primary key(s). To disable this field pass to the constructor sort=None

[coveralls]

Coverage increased (+1.4%) to 92.486% when pulling fb6913b on CaselIT:sortable_field into 8cb52a1 on graphql-python:master.

[exit99]

This going to get merged?

[CaselIT]

I hope so.
@syrusakbary could you review this PR?
Thanks

[CaselIT]

@syrusakbary see #104 (comment)

[YehonatanVonage]

Hi,
Any updates about this PR?

[CaselIT]

On my part I wanted a feedback from @syrusakbary about the implementation before writing the tests.

[millicentachieng]

@syrusakbary We are waiting on you to review the PR

[syrusakbary]

Sorry for the time taken on reviewing this PR, and thanks for the ping.
It looks good, once it have tests related to the new functionality I'll merge :)

[CaselIT]

Thanks for the review @syrusakbary
I'll work on adding the tests and ping you once they are done

[CaselIT]

@syrusakbary I think it's ready for a review
I've added the tests
Updated the implementation to support graphene v2
Added a documentation example and updated some other documentation to be compatible with v2

Let me know what you think

[syrusakbary]

It looks great! You did a great job 👏

Merging

[CaselIT]

Thank you for merging it!