Remove redundant matching of multipart content-type.

lib/openapi_first/request.rb

@@ -54,9 +54,6 @@ def operation_id
       @operation['operationId']
     end
 
-    MULTIPART_CONTENT_TYPE = %r{\Amultipart/form-data\b}i
-    private_constant :MULTIPART_CONTENT_TYPE
-
     private
 
     def parse_request(request, route_params:)
@@ -82,11 +79,7 @@ def parse_query(query_string)
     end
 
     def build_body_parser(content_type, encoding)
-      if content_type.match?(MULTIPART_CONTENT_TYPE)
-        RequestBodyParsers['multipart/form-data'].new(encoding: encoding || {})
-      else
-        RequestBodyParsers[content_type]
-      end
+      RequestBodyParsers[content_type, { encoding: encoding || {} }]
     end
   end
 end

lib/openapi_first/request_body_parsers.rb

@@ -14,9 +14,12 @@ def register(pattern, parser)
         parsers[pattern] = parser
       end
 
-      def [](content_type)
+      def [](content_type, options = {})
         key = parsers.keys.find { content_type.match?(_1) }
-        parsers.fetch(key) { DEFAULT }
+        parser = parsers.fetch(key) { DEFAULT }
+        return parser if parser.respond_to?(:call)
+
+        parser.new(options)
       end
     end
 
@@ -44,12 +47,8 @@ def self.read_body(request)
     # `contentType: application/json` (or any */json), the field's raw value
     # is JSON-parsed before schema validation.
     class MultipartBodyParser
-      def initialize(encoding: {})
-        @encoding = encoding || {}
-      end
-
-      def self.call(request)
-        new.call(request)
+      def initialize(options)
+        @encoding = options[:encoding] || {}
       end
 
       def call(request)
@@ -89,7 +88,7 @@ def unpack_value(value)
       end
     end
 
-    register('multipart/form-data', MultipartBodyParser)
+    register(%r{\Amultipart/form-data\b}i, MultipartBodyParser)
 
     register('application/x-www-form-urlencoded', lambda(&:POST))
   end

spec/request_body_parsers_spec.rb

@@ -29,9 +29,8 @@ def app = ->(_env) { Rack::Response.new.finish }
 
     context 'with an encoding map' do
       subject(:parser) do
-        OpenapiFirst::RequestBodyParsers::MultipartBodyParser.new(
-          encoding: { 'data' => { 'contentType' => 'application/json' } }
-        )
+        options = { encoding: { 'data' => { 'contentType' => 'application/json' } } }
+        described_class['multipart/form-data', options]
       end
 
       it 'parses fields whose encoding contentType is JSON' do