Adding a new transport class to handle Phoenix channels

[leruaa]

First of all, thank you for this great library !

I'm building a tool that connect to a server built on Absinthe. This toolkit relies on the Phoenix framework channels feature to handle GraphQL subscriptions.

So I created a PhoenixChannelWebsocketsTransport class that implement all the logic to subscribe and receive data from a Phoenix channel.

Of course I'm open to any suggestions to improve this PR

[coveralls]

Coverage decreased (-0.5%) to 99.483% when pulling 28ad41d on acatinon:feature-phoenix-channel into faadac4 on graphql-python:master.

[KingDarBoja]

Not an expert on Elixir related framework/libraries but this transport class could be added as extra optional feature so any Elixir (Phoenix in this case) user can install it by running the following command:

pip install gql[phoenix-transport]

@leszekhanusz what do you think?

Also, I will take a look at it whenever I can, currently busy with some graphql-server-core stuff.

[leszekhanusz]

Very interesting.
I like how this transport inherits the websockets transport.
I tried to find a spec which describe the protocol implemented here but I have not found it. Could you please add a link to it ?

[leruaa]

I tried to find a spec which describe the protocol implemented here but I have not found it. Could you please add a link to it ?

@leszekhanusz Unfortunately I didn't find any specs for Phoenix channels either. There are pointers to some docs in this thread, but i've mainly done reverse engineering on the C# Phoenix client project.

Btw I will take your feedbacks into account.

[leruaa]

@leszekhanusz I finished taking your comments into account.

[leruaa]

Do you need me to further improve the test coverage on this PR ?

[KingDarBoja]

Do you need me to further improve the test coverage on this PR ?

The /gql/transport/phoenix_channel_websockets.py has 96.26% of coverage as seen at coveralls report, but I think it is pretty high already.

So don't worry about it at the moment.

[KingDarBoja]

@acatinon updating with the latest changes from master should bring coverage to 100%, also there is few mypy errors on the phoenix transport.

[leruaa]

@KingDarBoja Done.

[KingDarBoja]

This one is almost ready to merge, only thing left is increasing coverage to 100%.

cc @leszekhanusz

[KingDarBoja]

Coverage reached 100% 🚀

[leszekhanusz]

Coverage reached 100% rocket

I cheated a little and just added pragmas for the few remaining lines...

[leszekhanusz]

@acatinon Thanks again for this PR and sorry for the delay