Include detected file mime type in validate_mime_type_inclusion errors

lib/shrine/plugins/validation_helpers.rb

@@ -13,7 +13,10 @@ module ValidationHelpers
         min_height:          -> (min)  { "height must not be less than #{min}px" },
         max_dimensions:      -> (dims) { "dimensions must not be greater than #{dims.join("x")}" },
         min_dimensions:      -> (dims) { "dimensions must not be less than #{dims.join("x")}" },
-        mime_type_inclusion: -> (list) { "type must be one of: #{list.join(", ")}" },
+        mime_type_inclusion: lambda do |list, type|
+          mime_type = type == '' || type.nil? ? "no" : type
+          "type must be one of: #{list.join(", ")}, (#{mime_type} content type detected)"
+        end,
         mime_type_exclusion: -> (list) { "type must not be one of: #{list.join(", ")}" },
         extension_inclusion: -> (list) { "extension must be one of: #{list.join(", ")}" },
         extension_exclusion: -> (list) { "extension must not be one of: #{list.join(", ")}" },
@@ -172,7 +175,7 @@ def validate_dimensions((width_range, height_range))
         def validate_mime_type_inclusion(types, message: nil)
           validate_result(
             types.include?(file.mime_type),
-            :mime_type_inclusion, message, types
+            :mime_type_inclusion, message, types, file.mime_type
           )
         end
         alias validate_mime_type validate_mime_type_inclusion
@@ -230,9 +233,9 @@ def add_error(*args)
 
         # Returns the direct message if given, otherwise uses the default error
         # message.
-        def error_message(type, message, object)
+        def error_message(type, message, *args)
           message ||= self.class.default_validation_messages.fetch(type)
-          message.is_a?(String) ? message : message.call(object)
+          message.is_a?(String) ? message : message.call(*args)
         end
       end
     end

test/plugin/validation_helpers_test.rb

@@ -615,23 +615,26 @@
       @attacher.attach(fakeio(content_type: nil))
       @attacher.class.validate { validate_mime_type_inclusion(["image/jpeg"]) }
       @attacher.validate
-      assert_equal 1, @attacher.errors.size
+      assert_equal ["type must be one of: image/jpeg, (no content type detected)"], @attacher.errors
     end
 
     it "uses the default error message" do
       @attacher.class.validate { validate_mime_type_inclusion(["video/mpeg"]) }
       @attacher.validate
-      assert_equal ["type must be one of: video/mpeg"], @attacher.errors
+      assert_equal ["type must be one of: video/mpeg, (image/jpeg content type detected)"], @attacher.errors
     end
 
     it "accepts a custom error message" do
       @attacher.class.validate { validate_mime_type_inclusion(["video/mpeg"], message: "must be a video") }
       @attacher.validate
       assert_equal ["must be a video"], @attacher.errors
 
-      @attacher.class.validate { validate_mime_type_inclusion(["video/mpeg"], message: ->(whitelist){"must be #{whitelist.join(", ")}"}) }
+      @attacher.class.validate do
+        validate_mime_type_inclusion(["video/mpeg"],
+                                     message: ->(whitelist, type) {"must be #{whitelist.join(", ")}, #{type} detected"})
+      end
       @attacher.validate
-      assert_equal ["must be video/mpeg"], @attacher.errors
+      assert_equal ["must be video/mpeg, image/jpeg detected"], @attacher.errors
     end
 
     it "handles multiline mime types" do
@@ -656,7 +659,7 @@
     it "is aliased to #validate_mime_type" do
       @attacher.class.validate { validate_mime_type(["video/mpeg"]) }
       @attacher.validate
-      assert_equal ["type must be one of: video/mpeg"], @attacher.errors
+      assert_equal ["type must be one of: video/mpeg, (image/jpeg content type detected)"], @attacher.errors
     end
   end
 
@@ -890,7 +893,7 @@
       max_size: -> (max) { "is too big" }
     }
     @attacher.shrine_class.plugin :validation_helpers, default_messages: {
-      mime_type_inclusion: -> (list) { "is forbidden" }
+      mime_type_inclusion: -> (list, _type) { "is forbidden" }
     }
     @attacher.class.validate do
       validate_max_size 1