feat: add form_pairs support for Rack 3.2 compat

Author: chadlwilson

src/main/ruby/rack/handler/servlet/servlet_env.rb

@@ -49,6 +49,8 @@ def load_env_key(env, key)
         FORM_INPUT = "rack.request.form_input".freeze
         # @private
         FORM_HASH = "rack.request.form_hash".freeze
+        # @private
+        FORM_PAIRS = "rack.request.form_pairs".freeze # Rack 3.2+
 
         # @private
         POST_PARAM_METHODS = [ 'POST', 'PUT', 'DELETE' ].freeze
@@ -59,6 +61,7 @@ def load_parameters
           get_only = ! POST_PARAM_METHODS.include?( @servlet_env.getMethod )
           # we only need to really do this for POSTs but we'll handle all
           query_params, form_params = query_parser.make_params, query_parser.make_params
+          form_pairs = [] # raw (un-nested) POST name/value pairs for Rack 3.2+
           # NOTE: HttpServletRequest#getParameterMap merges query-string and
           # (POST) body parameters and exposes *every* raw value per name -
           # including repeated names that do not end with '[]' and names that
@@ -84,11 +87,13 @@ def load_parameters
                 end
                 store_parameter(query_params, key, get_vals)
                 store_parameter(form_params, key, post_vals)
+                post_vals.each { |v| form_pairs << [ key, v ] }
               else
                 store_parameter(query_params, key, val)
               end
             else # POST param :
               store_parameter(form_params, key, val)
+              val.each { |v| form_pairs << [ key, v ] }
             end
           end
           # Rack::Request#GET
@@ -98,6 +103,8 @@ def load_parameters
           # TODO should recreate the input e.g. multipart/form-data ...
           @env[ FORM_INPUT ] = @env['rack.input']
           @env[ FORM_HASH ] = form_params.to_h
+          # Rack::Request#form_pairs (Rack 3.2+, ignored by older Rack)
+          @env[ FORM_PAIRS ] = form_pairs
         end
 
         def [](key)

src/spec/ruby/rack/handler/servlet_spec.rb

@@ -956,6 +956,15 @@ def servlet.create_env(servlet_env)
                                           "name" => ["Ferko Suska", "Jozko Hruska"], "formula" => "a + b == 42%!"
                                         })
 
+      if rack_request.respond_to?(:form_pairs) # Rack 3.2+
+        # POST name/value pairs, preserving duplicate (raw, un-nested) names,
+        # available even though the servlet input stream was already consumed
+        expect(rack_request.form_pairs).to match_array([
+          [ 'name[]', 'Ferko Suska' ], [ 'name[]', 'Jozko Hruska' ],
+          [ 'age', '30' ], [ 'formula', 'a + b == 42%!' ]
+        ])
+      end
+
       expect(rack_request.query_string).to eq 'foo=bad&foo=bar&bar=huu&age=33'
       expect(rack_request.request_method).to eq 'POST'
       expect(rack_request.path_info).to eq '/path'