Gracefully handle the rename of Status 422 Unprocessable Content

[alassek]

Rack 3 changed the symbolic name of 422 from :unprocessable_entity to :unprocessable_content.

This follows from the rename in the HTTP spec. https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/422

[alassek]

Simplest way I could think to determine this with a minimum of allocations

[afomera]

I was thinking we could just use Rack::VERSION to check against rather than dropping this far, but rack 2's version const is... weird.

I think I might change that second version call for to_s as Gem::Version does respond with a string version

Gem.loaded_specs["rack"].version.to_s.start_with?("3")

± be hanami console
forked[development]> Gem.loaded_specs["rack"].version.to_s.start_with?("3")
=> true
forked[development]> Gem.loaded_specs["rack"].version.to_s
=> "3.2.3"

and in rack 2

± be hanami console
forked[development]> Rack::VERSION
=> [1, 3]
forked[development]> Rack
=> Rack
forked[development]> Rack::VERSION.to_s
=> "[1, 3]"
forked[development]> Gem.loaded_specs["rack"].version.version
=> "2.2.20"
forked[development]> Gem.loaded_specs["rack"].version
=> Gem::Version.new("2.2.20")
forked[development]> Gem.loaded_specs["rack"].version.to_s
=> "2.2.20"
forked[development]> Gem.loaded_specs["rack"].version.to_s
=> "2.2.20"
forked[development]> Gem.loaded_specs["rack"].version.class
=> Gem::Version
forked[development]> Gem.loaded_specs["rack"].version.version
=> "2.2.20"
forked[development]> Gem.loaded_specs["rack"].version.to_s
=> "2.2.20"

[alassek]

Gem::Version#to_s appears to be an alias to #version

[timriley]

We have a simple check for this that you can reuse: Hanami::Action.rack_3? See lib/hanami/action/rack_utils.rb and feel free to grep for it across the repo to see how we use it.

That said, based on my comment below, we may no longer need a Rack version check for this PR.

[aaronmallen]

How do we feel about keeping :unprocessable_entity in addition to the new symbol for backwards compatibility?

[timriley]

I think that because we've documented unprocessable_entity, it would be good for us to maintain it in the future.

I think for our 2.3 docs, we should show both unprocessable_content and unprocessable_content as working for 422, and should update this PR to work with both, for either version of Rack.

This feels important during this Rack v2/v3 transitional phase, which I expect we might keep for ~a year or so.

I think this might also simplify this PR? We'd just merge unprocessable_content and unprocessable_content keys into our SYMBOLS hash regardless of the version of rack we see being used?

[timriley]

Thank you so much for doing this, @alassek! This will take away one little hitch for our users and hopefully make their upgrade nicer :)

I've left a thought via a comment about a change in approach. Keen to hear what you think.

[timriley]

We have a simple check for this that you can reuse: Hanami::Action.rack_3? See lib/hanami/action/rack_utils.rb and feel free to grep for it across the repo to see how we use it.

That said, based on my comment below, we may no longer need a Rack version check for this PR.

[timriley]

I think that because we've documented unprocessable_entity, it would be good for us to maintain it in the future.

I think for our 2.3 docs, we should show both unprocessable_content and unprocessable_content as working for 422, and should update this PR to work with both, for either version of Rack.

This feels important during this Rack v2/v3 transitional phase, which I expect we might keep for ~a year or so.

I think this might also simplify this PR? We'd just merge unprocessable_content and unprocessable_content keys into our SYMBOLS hash regardless of the version of rack we see being used?

[alassek]

@timriley yep that's a cleaner approach, but good to know we have a helper for that.

I've also opened a documentation PR at hanami/guides#308

[timriley]

Thanks @alassek, looks great!

[timriley]

This is clever! 😄

[alassek]

Written originally for activerecord-pg_enum, I needed very fine-grained version distinction for my test suite