New feature : linting (ruby-grape#2557)

* Add linting feature through Grape.config and `lint_api!` method
Add spec
All specs are now linted

* Remove error message for Lint::Error

* Add ruby 3.1 to 3.2 to spec integrations
Add `yaml-dev` in Dockerfile

* Rename `lint_api!` to `lint!`

* Revert test.yml

* Add README.md and CHANGELOG.md
Fix typo in UPGRADING.md

* Fix CHANGELOG

* Use `lint!` in rails spec

* Fix api_spec lint with ensure

---------

Co-authored-by: Daniel (dB.) Doubrovkine <[email protected]>

Author: ericproulx

CHANGELOG.md

@@ -12,6 +12,7 @@
 * [#2554](https://github.com/ruby-grape/grape/pull/2554): Remove `Grape::Http::Headers` and `Grape::Util::Lazy::Object` - [@ericproulx](https://github.com/ericproulx).
 * [#2556](https://github.com/ruby-grape/grape/pull/2556): Remove unused `Grape::Request::DEFAULT_PARAMS_BUILDER` constant - [@eriklovmo](https://github.com/eriklovmo).
 * [#2558](https://github.com/ruby-grape/grape/pull/2558): Add Ruby's option `enable_frozen_string_literal` in CI - [@ericproulx](https://github.com/ericproulx).
+* [#2557](https://github.com/ruby-grape/grape/pull/2557): Add lint! - [@ericproulx](https://github.com/ericproulx).
 * Your contribution here.
 
 #### Fixes

README.md

@@ -28,6 +28,8 @@
     - [Header](#header)
     - [Accept-Version Header](#accept-version-header)
     - [Param](#param)
+- [Linting](#linting)
+  - [Bug in Rack::ETag under Rack 3.X](#bug-in-racketag-under-rack-3x)
 - [Describing Methods](#describing-methods)
 - [Configuration](#configuration)
 - [Parameters](#parameters)
@@ -650,6 +652,27 @@ version 'v1', using: :param, parameter: 'v'
     curl http://localhost:9292/statuses/public_timeline?v=v1
 
 
+## Linting
+
+You can check whether your API is in conformance with the [Rack's specification](https://github.com/rack/rack/blob/main/SPEC.rdoc) by calling `lint!` at the API level or through [configuration](#configuration).
+
+```ruby
+class Api < Grape::API
+  lint!
+end
+```
+```ruby
+Grape.configure do |config|
+  config.lint = true
+end
+```
+```ruby
+Grape.config.lint = true
+```
+
+### Bug in Rack::ETag under Rack 3.X
+If you're using Rack 3.X and the `Rack::Etag` middleware (used by [Rails](https://guides.rubyonrails.org/rails_on_rack.html#inspecting-middleware-stack)), a [bug](https://github.com/rack/rack/pull/2324) related to linting has been fixed in [3.1.13](https://github.com/rack/rack/blob/v3.1.13/CHANGELOG.md#3113---2025-04-13) and [3.0.15](https://github.com/rack/rack/blob/v3.1.13/CHANGELOG.md#3015---2025-04-13) respectively.
+
 ## Describing Methods
 
 You can add a description to API methods and namespaces. The description would be used by [grape-swagger][grape-swagger] to generate swagger compliant documentation.

UPGRADING.md

@@ -130,7 +130,7 @@ When using together with `Grape::Extensions::Hash::ParamBuilder`, `route_param`
 This was a regression introduced by [#2326](https://github.com/ruby-grape/grape/pull/2326) in Grape v1.8.0.
 
 ```ruby
-grape.configure do |config|
+Grape.configure do |config|
   config.param_builder = Grape::Extensions::Hash::ParamBuilder
 end
 

docker/Dockerfile

@@ -7,7 +7,7 @@ ENV RUBYOPT --enable-frozen-string-literal --yjit
 ENV LD_PRELOAD libjemalloc.so.2
 ENV MALLOC_CONF dirty_decay_ms:1000,narenas:2,background_thread:true
 
-RUN apk add --update --no-cache make gcc git libc-dev gcompat jemalloc && \
+RUN apk add --update --no-cache make gcc git libc-dev yaml-dev gcompat jemalloc && \
     gem update --system && gem install bundler
 
 WORKDIR $LIB_PATH

lib/grape.rb

@@ -75,6 +75,7 @@ def self.deprecator
 
   configure do |config|
     config.param_builder = :hash_with_indifferent_access
+    config.lint = false
     config.compile_methods!
   end
 end

lib/grape/dsl/routing.rb

@@ -72,10 +72,14 @@ def do_not_route_head!
         namespace_inheritable(:do_not_route_head, true)
       end
 
-      # Do not automatically route OPTIONS.
-      def do_not_route_options!
-        namespace_inheritable(:do_not_route_options, true)
-      end
+        # Do not automatically route OPTIONS.
+        def do_not_route_options!
+          namespace_inheritable(:do_not_route_options, true)
+        end
+
+        def lint!
+          namespace_inheritable(:lint, true)
+        end
 
       def do_not_document!
         namespace_inheritable(:do_not_document, true)

lib/grape/endpoint.rb

@@ -359,6 +359,7 @@ def build_stack(helpers)
       format = namespace_inheritable(:format)
 
       stack.use Rack::Head
+      stack.use Rack::Lint if lint?
       stack.use Class.new(Grape::Middleware::Error),
                 helpers: helpers,
                 format: format,
@@ -409,5 +410,9 @@ def build_response_cookies
         Rack::Utils.set_cookie_header! header, name, cookie_value
       end
     end
+
+    def lint?
+      namespace_inheritable(:lint) || Grape.config.lint
+    end
   end
 end

spec/grape/api_spec.rb

@@ -4738,4 +4738,28 @@ def uniqe_id_route
       expect(last_response.body).to eq('unknown params_builder: unknown')
     end
   end
+
+  describe '.lint!' do
+    let(:app) do
+      Class.new(described_class) do
+        lint!
+        get '/' do
+          status 42
+        end
+      end
+    end
+
+    around do |example|
+      @lint = Grape.config.lint
+      Grape.config.lint = false
+      example.run
+    ensure
+      Grape.config.lint = @lint
+    end
+
+    it 'raises a Rack::Lint error' do
+      # Status must be an Integer >= 100
+      expect { get '/' }.to raise_error(Rack::Lint::LintError)
+    end
+  end
 end

spec/integration/rails/mounting_spec.rb

@@ -4,6 +4,7 @@
   context 'rails mounted' do
     let(:api) do
       Class.new(Grape::API) do
+        lint!
         get('/test_grape') { 'rails mounted' }
       end
     end
@@ -28,7 +29,7 @@
           mount GrapeApi => '/'
 
           get 'up', to: lambda { |_env|
-            ['200', {}, ['hello world']]
+            [200, {}, ['hello world']]
           }
         end
       end

spec/spec_helper.rb

@@ -13,6 +13,7 @@
   end
 end
 
+Grape.config.lint = true # lint all apis by default
 Grape::Util::Registry.include(Deregister)
 # issue with ruby 2.7 with ^. We need to extend it again
 Grape::Validations.extend(Grape::Util::Registry) if Gem::Version.new(RUBY_VERSION).release < Gem::Version.new('3.0')