Skip validation if the format is binary, even if the value is not an actual string.

lib/openapi_parser/schema_validator/string_validator.rb

@@ -8,7 +8,18 @@ def initialize(validator, coerce_value, datetime_coerce_class)
     end
 
     def coerce_and_validate(value, schema, **_keyword_args)
-      return OpenAPIParser::ValidateError.build_error_result(value, schema) unless value.kind_of?(String)
+      unless value.kind_of?(String)
+        # Skip validation if the format is `binary`, even if the value is not an actual string.
+        # ref: https://github.com/OAI/OpenAPI-Specification/blob/main/versions/3.0.3.md#data-types
+        if schema.format == 'binary'
+          # TODO:
+          # It would be better to check whether the value is an instance of `Rack::Multipart::UploadFile`,
+          # `ActionDispatch::Http::UploadedFile`, or another similar class.
+          return [value, nil]
+        end
+
+        return OpenAPIParser::ValidateError.build_error_result(value, schema)
+      end
 
       value, err = check_enum_include(value, schema)
       return [nil, err] if err

spec/openapi_parser/schema_validator/string_validator_spec.rb

@@ -378,4 +378,24 @@
       end
     end
   end
+
+  describe 'validate binary format' do
+    subject { OpenAPIParser::SchemaValidator.validate(params, target_schema, options) }
+
+    let(:replace_schema) do
+      {
+        binary: {
+          type: 'string',
+          format: 'binary',
+        },
+      }
+    end
+
+    context 'correct' do
+      context 'arbitrary object except string' do
+        let(:params) { { 'binary' => ['b', 'i', 'n', 'a', 'r', 'y'] } }
+        it { expect(subject).to eq({ 'binary' => ['b', 'i', 'n', 'a', 'r', 'y'] }) }
+      end
+    end
+  end
 end