Simplify Rack 3 support using Rack::Headers

The `Rack::Headers` subclass of `Hash` was added in Rack 3, and is meant
to help libraries support both Rack 2 and 3. I was concerned whether
returning `Rack::Headers` instead of `Hash` to the end user was
backwards compatible, but it seems that both Roda and Rack are doing it,
so it should be safe.

We remove Appraisal and for now let Rack 2 be tested implicitly with
Ruby 2.3, as Rack 3 requires Ruby 2.4+. But I don't think we need to be
testing Rack 2.x support, especially now that we've removed duplication,
I would be surprised if it breaks. With `Rack::Headers` we were able to
keep Ruby 2.3 support, as we're not using `Hash#transform_keys` anymore.

I also switched from rack-test_app, which seems to be unmaintained, back
to rack-test, which is the established library for testing Rack apps.
Ever since Jeremy Evans took over maintenance, it's gotten a lot better
and more flexible, so it's completely viable for Shrine's needs. Since
rack-test returns `Rack::Headers`, we were able to remove the header
constants.

.github/workflows/ci.yml

@@ -24,6 +24,7 @@ jobs:
       fail-fast: false
       matrix:
         ruby:
+          - "2.3"
           - "2.4"
           - "2.5"
           - "2.6"
@@ -33,9 +34,6 @@ jobs:
           - "3.2"
           - "3.3"
           - "jruby-9.4"
-        rack:
-          - "2"
-          - "3"
 
     steps:
       - uses: actions/checkout@v3
@@ -55,7 +53,7 @@ jobs:
           ${GITHUB_WORKSPACE}/minio/minio server ${GITHUB_WORKSPACE}/minio/data --address localhost:9000 &>${GITHUB_WORKSPACE}/minio/data/server.log &
 
       - name: Install dependencies
-        run: bundle exec appraisal install
+        run: bundle install
 
       - name: Run tests
-        run: bundle exec appraisal rack-${{ matrix.rack }} rake test
+        run: bundle exec rake test

Gemfile

@@ -7,4 +7,4 @@ gem "simplecov"
 
 gem "hanna", require: false
 
-gem "activerecord-jdbcsqlite3-adapter", "~> 51.0", platform: :jruby if RUBY_ENGINE == "jruby"
+gem "activerecord-jdbcsqlite3-adapter", "~> 70.0", platform: :jruby if RUBY_ENGINE == "jruby"

lib/shrine/plugins/derivation_endpoint.rb

@@ -365,16 +365,9 @@ def call(env)
         handle_request(request)
       end
 
-      headers ||= {}
-
-      if Rack.release >= "3"
-        headers["content-length"] ||= body.respond_to?(:bytesize) ? body.bytesize.to_s :
-                                                                    body.map(&:bytesize).inject(0, :+).to_s
-      else
-        headers["Content-Length"] ||= body.map(&:bytesize).inject(0, :+).to_s
-      end
-
-      headers = headers.transform_keys(&:downcase) if Rack.release >= "3"
+      headers = Rack::Headers[headers]
+      headers["Content-Length"] ||= body.respond_to?(:bytesize) ? body.bytesize.to_s :
+                                                                  body.map(&:bytesize).inject(0, :+).to_s
 
       [status, headers, body]
     end
@@ -420,8 +413,6 @@ def handle_request(request)
         headers["Cache-Control"] = derivation.option(:cache_control)
       end
 
-      headers = headers.transform_keys(&:downcase) if Rack.release >= "3"
-
       [status, headers, body]
     end
 
@@ -455,11 +446,7 @@ def expires_in(request)
 
     # Halts the request with the error message.
     def error!(status, message)
-      headers = { "Content-Type" => "text/plain" }
-
-      headers = headers.transform_keys(&:downcase) if Rack.release >= "3"
-
-      throw :halt, [status, headers, [message]]
+      throw :halt, [status, { "Content-Type" => "text/plain" }, [message]]
     end
 
     def secret_key
@@ -496,33 +483,20 @@ def local_response(env)
     # `Content-Type` and `Content-Disposition` response headers from derivation
     # options and file extension of the derivation result.
     def file_response(file, env)
-      response = rack_file_response(file.path, env)
-
-      status = response[0]
-
-      headers = if Rack.release >= "3"
-        {
-          "content-type"        => type || response[1]["content-type"],
-          "content-length"      => response[1]["content-length"],
-          "content-disposition" => content_disposition(file),
-          "content-range"       => response[1]["content-range"],
-          "accept-ranges"       => "bytes",
-        }.compact
-      else
-        {
-          "Content-Type"        => type || response[1]["Content-Type"],
-          "Content-Length"      => response[1]["Content-Length"],
-          "Content-Disposition" => content_disposition(file),
-          "Content-Range"       => response[1]["Content-Range"],
-          "Accept-Ranges"       => "bytes",
-        }.compact
-      end
+      status, headers, body = rack_file_response(file.path, env)
 
-      body = Rack::BodyProxy.new(response[2]) { File.delete(file.path) }
+      headers = Rack::Headers[headers] if Rack.release >= "3"
+      headers = {
+        "Content-Type"        => type || headers["Content-Type"],
+        "Content-Length"      => headers["Content-Length"],
+        "Content-Disposition" => content_disposition(file),
+        "Content-Range"       => headers["Content-Range"],
+        "Accept-Ranges"       => "bytes",
+      }.compact
 
-      file.close
+      body = Rack::BodyProxy.new(body) { File.delete(file.path) }
 
-      headers = headers.transform_keys(&:downcase) if Rack.release >= "3"
+      file.close
 
       [status, headers, body]
     end
@@ -541,8 +515,10 @@ def upload_response(env)
 
       if upload_redirect
         redirect_url = uploaded_file.url(**upload_redirect_url_options)
+        headers = { "Location" => redirect_url }
+        headers = Rack::Headers[headers] if Rack.release >= "3"
 
-        [302, { "Location" => redirect_url }, []]
+        [302, headers, []]
       else
         if derivative && File.exist?(derivative.path)
           file_response(derivative, env)

lib/shrine/plugins/download_endpoint.rb

@@ -113,14 +113,9 @@ def call(env)
         handle_request(request)
       end
 
-      if Rack.release >= "3"
-        headers["content-length"] ||= body.respond_to?(:bytesize) ? body.bytesize.to_s :
-                                                                    body.map(&:bytesize).inject(0, :+).to_s
-      else
-        headers["Content-Length"] ||= body.map(&:bytesize).inject(0, :+).to_s
-      end
-
-      headers = headers.transform_keys(&:downcase) if Rack.release >= "3"
+      headers = Rack::Headers[headers] if Rack.release >= "3"
+      headers["Content-Length"] ||= body.respond_to?(:bytesize) ? body.bytesize.to_s :
+                                                                  body.map(&:bytesize).inject(0, :+).to_s
 
       [status, headers, body]
     end
@@ -204,11 +199,7 @@ def bad_request!(message)
 
     # Halts the request with the error message.
     def error!(status, message)
-      headers = { "Content-Type" => "text/plain" }
-
-      headers = headers.transform_keys(&:downcase) if Rack.release >= "3"
-
-      throw :halt, [status, headers, [message]]
+      throw :halt, [status, { "Content-Type" => "text/plain" }, [message]]
     end
   end
 end

lib/shrine/plugins/presign_endpoint.rb

@@ -91,14 +91,9 @@ def call(env)
         end
       end
 
-      if Rack.release >= "3"
-        headers["content-length"] ||= body.respond_to?(:bytesize) ? body.bytesize.to_s :
-                                                                    body.map(&:bytesize).inject(0, :+).to_s
-      else
-        headers["Content-Length"] ||= body.map(&:bytesize).inject(0, :+).to_s
-      end
-
-      headers = headers.transform_keys(&:downcase) if Rack.release >= "3"
+      headers = Rack::Headers[headers] if Rack.release >= "3"
+      headers["Content-Length"] ||= body.respond_to?(:bytesize) ? body.bytesize.to_s :
+                                                                  body.map(&:bytesize).inject(0, :+).to_s
 
       [status, headers, body]
     end
@@ -165,25 +160,22 @@ def generate_presign(location, options, request)
     # headers, and a body enumerable. If `:rack_response` option is given,
     # calls that instead.
     def make_response(object, request)
-      if @rack_response
-        response = @rack_response.call(object, request)
+      status, headers, body = if @rack_response
+        @rack_response.call(object, request)
       else
-        response = [200, { "Content-Type" => CONTENT_TYPE_JSON }, [object.to_json]]
+        [200, { "Content-Type" => CONTENT_TYPE_JSON }, [object.to_json]]
       end
 
+      headers = Rack::Headers[headers] if Rack.release >= "3"
       # prevent browsers from caching the response
-      response[1]["Cache-Control"] = "no-store" unless response[1].key?("Cache-Control")
+      headers["Cache-Control"] = "no-store" unless headers.key?("Cache-Control")
 
-      response
+      [status, headers, body]
     end
 
     # Used for early returning an error response.
     def error!(status, message)
-      headers = { "Content-Type" => CONTENT_TYPE_TEXT }
-
-      headers = headers.transform_keys(&:downcase) if Rack.release >= "3"
-
-      throw :halt, [status, headers, [message]]
+      throw :halt, [status, { "Content-Type" => CONTENT_TYPE_TEXT }, [message]]
     end
 
     # Returns the uploader around the specified storage.

lib/shrine/plugins/rack_response.rb

@@ -32,11 +32,9 @@ def call(**options)
           headers = rack_headers(**options)
           body    = rack_body(**options)
 
-          if Rack.release >= "3"
-            [status, headers.transform_keys(&:downcase), body]
-          else
-            [status, headers, body]
-          end
+          headers = Rack::Headers[headers] if Rack.release >= "3"
+
+          [status, headers, body]
         end
 
         private

lib/shrine/plugins/upload_endpoint.rb

@@ -91,14 +91,9 @@ def call(env)
         handle_request(request)
       end
 
-      if Rack.release >= "3"
-        headers["content-length"] ||= body.respond_to?(:bytesize) ? body.bytesize.to_s :
-                                                                    body.map(&:bytesize).inject(0, :+).to_s
-      else
-        headers["Content-Length"] ||= body.map(&:bytesize).inject(0, :+).to_s
-      end
-
-      headers = headers.transform_keys(&:downcase) if Rack.release >= "3"
+      headers = Rack::Headers[headers] if Rack.release >= "3"
+      headers["Content-Length"] ||= body.respond_to?(:bytesize) ? body.bytesize.to_s :
+                                                                  body.map(&:bytesize).inject(0, :+).to_s
 
       [status, headers, body]
     end
@@ -217,11 +212,7 @@ def verify_checksum!(file, request)
 
     # Used for early returning an error response.
     def error!(status, message)
-      headers = { "Content-Type" => CONTENT_TYPE_TEXT }
-
-      headers = headers.transform_keys(&:downcase) if Rack.release >= "3"
-
-      throw :halt, [status, headers, [message]]
+      throw :halt, [status, { "Content-Type" => CONTENT_TYPE_TEXT }, [message]]
     end
 
     # Returns the uploader around the specified storage.

shrine.gemspec

@@ -37,15 +37,14 @@ direct uploads for fully asynchronous user experience.
   gem.add_dependency "content_disposition", "~> 1.0"
 
   # general testing helpers
-  gem.add_development_dependency "appraisal", "~> 2.5"
   gem.add_development_dependency "rake", ">= 11.1"
   gem.add_development_dependency "minitest", "~> 5.8"
   gem.add_development_dependency "mocha", "~> 1.11"
 
   # for endpoint plugins
   gem.add_development_dependency "rack", ">= 2", "< 4"
   gem.add_development_dependency "http-form_data", "~> 2.2"
-  gem.add_development_dependency "rack-test_app"
+  gem.add_development_dependency "rack-test", "~> 2.1"
 
   # for determine_mime_type plugin
   gem.add_development_dependency "mimemagic", ">= 0.3.2"