HTTPoison.Base behaviour

[JoeMerriweather-Webb]

This makes HTTPoison.Base a behaviour module.

This has the following benefits:

• Functions in the callback module that uses HTTPoison.Base can be marked with @impl
• It can now be used directly with Mox without a wrapping module.

This will cause warnings if the callback module using HTTPoison.Base overrides functions that are public with private ones.

[JoeMerriweather-Webb]

It looks like it does not work with behaviours to mix def and defp
and results in warnings like:

warning: function process_request_headers/1 required by behaviour HTTPoison.Base was implemented as "defp" but should have been "def" (in module HTTPoisonBaseTest.ExampleDefp)
    test/httpoison_base_test.exs:16

[whatyouhide]

I am all for making Base a behaviour, I think it's definitely the way to go. The problem with private functions is that callbacks have to be public by design, so you'd have to turn all those defps into public functions which would be a breaking change because people are implementing them as private functions and you expect them to implement those as public functions now. I don't know what a good solution might be other than living with the warnings and telling folks to update those functions to be public.

[edgurgel]

Yeah I think we can push this forward and make them public. I will play with it this week and we can release a new version soon. Thanks, @JosephMichaelWebb & @whatyouhide

[edgurgel]

Ok we can release this as a minor version as it's just a warning. I think it's ok to no bump a major version for this. I will release this soon ! Thanks 👍