add ability to set per param encoding

actionpack/lib/action_controller/metal.rb

@@ -135,7 +135,7 @@ def self.make_response!(request)
       end
     end
 
-    def self.binary_params_for?(action) # :nodoc:
+    def self.custom_encoding_for(action, param) # :nodoc:
       false
     end
 

actionpack/lib/action_controller/metal/parameter_encoding.rb

@@ -12,11 +12,11 @@ def inherited(klass) # :nodoc:
       end
 
       def setup_param_encode # :nodoc:
-        @_parameter_encodings = {}
+        @_parameter_encodings = Hash.new { |h, k| h[k] = {} }
       end
 
-      def binary_params_for?(action) # :nodoc:
-        @_parameter_encodings[action.to_s]
+      def custom_encoding_for(action, param) # :nodoc:
+        @_parameter_encodings[action.to_s][param.to_s]
       end
 
       # Specify that a given action's parameters should all be encoded as
@@ -44,7 +44,35 @@ def binary_params_for?(action) # :nodoc:
       # encoded as ASCII-8BIT. This is useful in the case where an application
       # must handle data but encoding of the data is unknown, like file system data.
       def skip_parameter_encoding(action)
-        @_parameter_encodings[action.to_s] = true
+        @_parameter_encodings[action.to_s] = Hash.new { Encoding::ASCII_8BIT }
+      end
+
+      # Specify the encoding for a a parameter on an action
+      # ASCII-8BIT (it "skips" the encoding default of UTF-8).
+      #
+      # For example, a controller would use it like this:
+      #
+      #   class RepositoryController < ActionController::Base
+      #     param_encoding :show, :file_path, Encoding::ASCII_8BIT
+      #
+      #     def show
+      #       @repo = Repository.find_by_filesystem_path params[:file_path]
+      #
+      #       # `repo_name` is guaranteed to be UTF-8, but was ASCII-8BIT, so
+      #       # tag it as such
+      #       @repo_name = params[:repo_name].force_encoding 'UTF-8'
+      #     end
+      #
+      #     def index
+      #       @repositories = Repository.all
+      #     end
+      #   end
+      #
+      # The file_path parameter on the show action would be encoded as ASCII-8BIT.
+      # This is useful in the case where an application must handle data
+      # but encoding of the data is unknown, like file system data.
+      def param_encoding(action, param, encoding)
+        @_parameter_encodings[action.to_s][param.to_s] = encoding
       end
     end
   end

actionpack/lib/action_dispatch/http/request.rb

@@ -76,7 +76,7 @@ def commit_cookie_jar! # :nodoc:
     PASS_NOT_FOUND = Class.new { # :nodoc:
       def self.action(_); self; end
       def self.call(_); [404, { "X-Cascade" => "pass" }, []]; end
-      def self.binary_params_for?(action); false; end
+      def self.custom_encoding_for(action, param); nil; end
     }
 
     def controller_class

actionpack/lib/action_dispatch/request/utils.rb

@@ -42,7 +42,7 @@ def self.check_param_encoding(params)
       end
 
       def self.set_binary_encoding(request, params, controller, action)
-        BinaryParamEncoder.encode(request, params, controller, action)
+        CustomParamEncoder.encode(request, params, controller, action)
       end
 
       class ParamEncoder # :nodoc:
@@ -78,23 +78,25 @@ def self.handle_array(params)
         end
       end
 
-      class BinaryParamEncoder # :nodoc:
+      class CustomParamEncoder # :nodoc:
         def self.encode(request, params, controller, action)
           return params unless controller && controller.valid_encoding?
 
-          if binary_params_for?(request, controller, action)
-            ActionDispatch::Request::Utils.each_param_value(params.except(:controller, :action)) do |param|
-              param.force_encoding ::Encoding::ASCII_8BIT
+          params.except(:controller, :action).each do |key, value|
+            # next if key == :controller || key == :action
+            ActionDispatch::Request::Utils.each_param_value(value) do |param|
+              if desired_encoding = custom_encoding_for(request, controller, action, key)
+                param.force_encoding(desired_encoding)
+              end
             end
           end
-
           params
         end
 
-        def self.binary_params_for?(request, controller, action)
-          request.controller_class_for(controller).binary_params_for?(action)
+        def self.custom_encoding_for(request, controller, action, param)
+          request.controller_class_for(controller).custom_encoding_for(action, param)
         rescue MissingController
-          false
+          nil
         end
       end
     end

actionpack/test/dispatch/request/multipart_params_parsing_test.rb

@@ -4,12 +4,10 @@
 
 class MultipartParamsParsingTest < ActionDispatch::IntegrationTest
   class TestController < ActionController::Base
+    skip_parameter_encoding("parse_binary")
+
     class << self
       attr_accessor :last_request_parameters, :last_parameters
-
-      def binary_params_for?(action)
-        action == "parse_binary"
-      end
     end
 
     def parse_binary

actionpack/test/dispatch/routing_test.rb

@@ -4559,9 +4559,7 @@ def app; APP end
 
 class TestInvalidUrls < ActionDispatch::IntegrationTest
   class FooController < ActionController::Base
-    def self.binary_params_for?(action)
-      action == "show"
-    end
+    param_encoding :show, :id, Encoding::ASCII_8BIT
 
     def show
       render plain: "foo#show"
@@ -4595,7 +4593,7 @@ def show
     end
   end
 
-  test "params encoded with binary_params_for? are treated as ASCII 8bit" do
+  test "params param_encoding uses ASCII 8bit" do
     with_routing do |set|
       set.draw do
         get "/foo/show(/:id)", to: "test_invalid_urls/foo#show"