Rewrite MergeErrorStrategy to work with Rails 6.1

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## master
 
+- [PR #6](https://github.com/DmitryTsepelev/store_model/pull/6) Rewrite MergeErrorStrategy to work with Rails 6.1 ([@DmitryTsepelev][])
+
 ## 0.2.0 (2019-04-30)
 
 - [PR #5](https://github.com/DmitryTsepelev/store_model/pull/5) Raise error when `#cast` cannot handle the passed instance ([@DmitryTsepelev][])

README.md

@@ -140,6 +140,8 @@ You can change the global behavior using `StoreModel.config`:
 StoreModel.config.merge_errors = true
 ```
 
+> Heads up! Due to the [changes](https://github.com/rails/rails/pull/32313) of error internals in Rails >= 6.1 it's impossible to add an error with a key that does not have a corresponding attribute with the same name. Because of that, behavior of `merge_error` strategy will be different - all errors are going to be placed under the attribute name (`{ configuration: ["Color can't be blank"] }` instead of `{ color: ["can't be blank"] }`).
+
 You can also add your own custom strategies to handle errors. All you need to do is to provide a callable object to `StoreModel.config.merge_errors` or as value of `:merge_errors`. It should accept three arguments - _attribute_, _base_errors_ and _store_model_errors_:
 
 ```ruby

lib/store_model/combine_errors_strategies/merge_error_strategy.rb

@@ -4,7 +4,13 @@ module StoreModel
   module CombineErrorsStrategies
     class MergeErrorStrategy
       def call(_attribute, base_errors, store_model_errors)
-        base_errors.copy!(store_model_errors)
+        if Rails::VERSION::MAJOR < 6 || Rails::VERSION::MAJOR == 6 && Rails::VERSION::MINOR.zero?
+          base_errors.copy!(store_model_errors)
+        else
+          store_model_errors.errors.each do |error|
+            base_errors.add(:configuration, :invalid, message: error.full_message)
+          end
+        end
       end
     end
   end

spec/store_model/combine_error_strategies/merge_error_strategy_spec.rb

@@ -19,8 +19,13 @@
   it "adds message that associated object is invalid" do
     described_class.new.call(:configuration, record.errors, record.configuration.errors)
 
-    expect(record.errors.messages).to eq(color: ["can't be blank"])
-    expect(record.errors.full_messages).to eq(["Color can't be blank"])
+    if Rails::VERSION::MAJOR < 6 || Rails::VERSION::MAJOR == 6 && Rails::VERSION::MINOR == 0
+      expect(record.errors.messages).to eq(color: ["can't be blank"])
+      expect(record.errors.full_messages).to eq(["Color can't be blank"])
+    else
+      expect(record.errors.messages).to eq(configuration: ["Color can't be blank"])
+      expect(record.errors.full_messages).to eq(["Configuration Color can't be blank"])
+    end
 
     expect(record.configuration.errors.messages).to eq(color: ["can't be blank"])
     expect(record.configuration.errors.full_messages).to eq(["Color can't be blank"])