fix: support non-lower-case Content-Type header provided by app

lib/pdfkit/middleware.rb

@@ -22,7 +22,8 @@ def _call(env)
       status, headers, response = @app.call(env)
 
       begin
-        if rendering_pdf? && headers['content-type'] =~ /text\/html|application\/xhtml\+xml/
+        content_type_header = headers.has_key?('Content-Type') ? 'Content-Type' : 'content-type'
+        if rendering_pdf? && headers[content_type_header] =~ /text\/html|application\/xhtml\+xml/
           body = response.respond_to?(:body) ? response.body : response.join
           body = body.join if body.is_a?(Array)
 
@@ -49,7 +50,7 @@ def _call(env)
           end
 
           headers['content-length'] = (body.respond_to?(:bytesize) ? body.bytesize : body.size).to_s
-          headers['content-type']   = 'application/pdf'
+          headers[content_type_header]   = 'application/pdf'
           headers['content-disposition'] ||= @conditions[:disposition] || 'inline'
         end
       rescue StandardError => e

spec/middleware_spec.rb

@@ -422,6 +422,29 @@ def mock_app(options = {}, conditions = {}, custom_headers = {})
       end
     end
 
+    describe "content type header" do
+      before { mock_app }
+
+      context "lower case" do
+        specify "header gets correctly updated" do
+          get 'http://www.example.org/public/test.pdf'
+          expect(last_response.headers["content-type"]).to eq("application/pdf")
+        end
+      end
+
+      context "mixed case" do
+        let(:headers) do
+          {'Content-Type' => "text/html"}
+        end
+
+        specify "header gets correctly updated" do
+          pending("this test only applies to rack 2.x and is rejected by rack 3.x") if Rack.release >= "3.0.0"
+          get 'http://www.example.org/public/test.pdf'
+          expect(last_response.headers["Content-Type"]).to eq("application/pdf")
+        end
+      end
+    end
+
     describe "remove .pdf from PATH_INFO and REQUEST_URI" do
       before { mock_app }