be_unprocessable_entity matcher not working with rack 3.1.x

[Aqualon]

Subject of the issue

Not sure where this fits, but I have an issue in a controller spec that should verify a 422 response.

it 'returns 422' do
  post :create, params: share_params
  expect(response).to be_unprocessable_entity
end

With rack 3.0.11 this works fine and via byebug found out that be_unprocessable_entity comes from rspec-expecations DSL

(byebug) be_unprocessable_entity
#<RSpec::Matchers::DSL::Matcher be_unprocessable_entity>
(byebug) method(:be_unprocessable_entity).source_location
["/Users/bruno.escherl/.asdf/installs/ruby/3.3.3/lib/ruby/gems/3.3.0/gems/rspec-expectations-3.13.1/lib/rspec/matchers/dsl.rb", 75]

Updating to rack 3.1.3 I get this error

Failure/Error: expect(response).to be_unprocessable_entity
       expected #<ActionDispatch::TestResponse:0x000000013573d530 @mon_data=#<Monitor:0x0000000135af03d0>, @mon_data_...equest POST "http://test.host/rest/activities/legacy/users/2322146568/activities.json" for 0.0.0.0>> to respond to `unprocessable_entity?

and checked again and this time get

(byebug) be_unprocessable_entity
#<RSpec::Matchers::BuiltIn::BePredicate:0x00000001317d6130 @method_name=:be_unprocessable_entity, @args=[], @block=nil>
(byebug) method(:be_unprocessable_entity).source_location
nil

So somehow updating rack causes be_unprocessable_entity to be something different?

I can change the expectation to expect(response).to be_unprocessable which still works, but would be curious what is up there?

Your environment

• Ruby version: 3.3.3
• rspec-expectations version: 3.13.1
• rails: 7.1.3.4

Steps to reproduce

Expected behavior

Actual behavior

[pirj]

be_unprocessable_entity comes from rspec-expecations DSL

It’s a generic predicate matcher, and it delegates to the underlying object.

The failure you’re seeing is most certainly due to a change in the rack API. You can read more about this here. In a minor version update you may still see breaking changes like this.

[Aqualon]

Thanks, seems to have been this change: rack/rack#2137. 422s were renamed from unprocessable_entity to unprocessable_content leading to the observed behavior.

[pirj]

@Aqualon What surprises me is how be_unprocessable_entity used to work. I can only see just the unprocessable? defined, and this hasn’t changed for a decade.

I was about to complain in that Rack PR that a predicate method has been removed/renamed, but I don’t see a clear trace where this happened.
Would you like to dig a bit deeper into this?

I don’t think that the Rack guys intended to break specs i a minor version except for printing a warning.

[pirj]

Maybe some metaprogramming in Rails that builds on too of Rack?

[pirj]

This is not the first time this happens, see Rails 4.2 notes. Was rack pinned in Rails back then?

[Aqualon]

I figured it out, the be_unprocessable_entity matcher was defined in our own codebase using

Rack::Utils::SYMBOL_TO_STATUS_CODE.each_pair do |symbol, status_code|
  RSpec::Matchers.define :"be_#{symbol}" do
    match do |actual|
      actual.present? && actual.code.to_s == status_code.to_s
    end
    failure_message do |actual|
      "expected response code to be #{status_code}, but was #{actual.code}"
    end
  end
end

and since Rack::Utils::SYMBOL_TO_STATUS_CODE now contains unprocessable_content: 422 instead of unprocessable_entity: 422, we don't get the matcher we used anymore.