decoupled form and multipart transcoder, moved check to Request::Body

lib/httpx/request/body.rb

@@ -127,8 +127,13 @@ module HTTPX
           # @type var body: bodyIO
           Transcoder::Body.encode(body)
         elsif (form = params.delete(:form))
-          # @type var form: Transcoder::urlencoded_input
-          Transcoder::Form.encode(form)
+          if Transcoder::Multipart.multipart?(form)
+            # @type var form: Transcoder::multipart_input
+            Transcoder::Multipart.encode(form)
+          else
+            # @type var form: Transcoder::urlencoded_input
+            Transcoder::Form.encode(form)
+          end
         elsif (json = params.delete(:json))
           # @type var body: _ToJson
           Transcoder::JSON.encode(json)

lib/httpx/transcoder/form.rb

@@ -48,11 +48,7 @@ module HTTPX
       end
 
       def encode(form)
-        if multipart?(form)
-          Multipart::Encoder.new(form)
-        else
-          Encoder.new(form)
-        end
+        Encoder.new(form)
       end
 
       def decode(response)
@@ -67,14 +63,6 @@ module HTTPX
           raise Error, "invalid form mime type (#{content_type})"
         end
       end
-
-      def multipart?(data)
-        data.any? do |_, v|
-          Multipart::MULTIPART_VALUE_COND.call(v) ||
-            (v.respond_to?(:to_ary) && v.to_ary.any?(&Multipart::MULTIPART_VALUE_COND)) ||
-            (v.respond_to?(:to_hash) && v.to_hash.any? { |_, e| Multipart::MULTIPART_VALUE_COND.call(e) })
-        end
-      end
     end
   end
 end

lib/httpx/transcoder/multipart.rb

@@ -13,5 +13,19 @@ module HTTPX::Transcoder
           value.key?(:body) &&
           (value.key?(:filename) || value.key?(:content_type)))
     end
+
+    module_function
+
+    def multipart?(form_data)
+      form_data.any? do |_, v|
+        Multipart::MULTIPART_VALUE_COND.call(v) ||
+          (v.respond_to?(:to_ary) && v.to_ary.any?(&Multipart::MULTIPART_VALUE_COND)) ||
+          (v.respond_to?(:to_hash) && v.to_hash.any? { |_, e| Multipart::MULTIPART_VALUE_COND.call(e) })
+      end
+    end
+
+    def encode(form_data)
+      Encoder.new(form_data)
+    end
   end
 end

sig/transcoder/form.rbs

@@ -3,14 +3,14 @@ module HTTPX::Transcoder
 
   type form_nested_value = form_value | _ToAry[form_value] | _ToHash[string, form_value]
 
-  type urlencoded_input = Enumerable[[_ToS, form_nested_value | Multipart::multipart_nested_value]]
+  type urlencoded_input = Enumerable[[_ToS, form_nested_value]]
 
   module Form
     PARAM_DEPTH_LIMIT: Integer
 
-    def self?.encode: (urlencoded_input form) -> (Encoder | Multipart::Encoder)
+    def self?.encode: (urlencoded_input form) -> Encoder
+
     def self?.decode: (HTTPX::Response response) -> _Decoder
-    def self?.multipart?: (form_nested_value | Multipart::multipart_nested_value data) -> bool
 
     class Encoder
       extend Forwardable

sig/transcoder/multipart.rbs

@@ -16,6 +16,12 @@ module HTTPX
 
       type multipart_nested_value = multipart_value | _ToAry[multipart_value] | _ToHash[string, multipart_value]
 
+      type multipart_input = Enumerable[[_ToS, Multipart::multipart_nested_value]]
+
+      def self?.encode: (multipart_input form_data) -> Multipart::Encoder
+
+      def self?.multipart?: (form_nested_value | multipart_nested_value form_data) -> bool
+
       class Encoder
         @boundary: String
         @part_index: Integer
@@ -36,9 +42,9 @@ module HTTPX
 
         private
 
-        def to_parts: (Enumerable[[Symbol | string, multipart_nested_value]] multipart_data) -> Array[_Reader]
+        def to_parts: (multipart_input multipart_data) -> Array[_Reader]
 
-        def initialize: (Enumerable[[Symbol | string, multipart_nested_value]] multipart_data) -> untyped
+        def initialize: (multipart_input multipart_data) -> untyped
 
         def header_part: (String key, String content_type, String? filename) -> StringIO