[Fix #737] Fix a false positive for `Rails/DeprecatedActiveModelError…

…sMethods`

Fixes #737.

This commit fixes a false positive for `Rails/DeprecatedActiveModelErrorsMethods`
when using `keys` method with Rails 6.0.

changelog/fix_a_false_positive_for_rails_deprecated_active_model_errors_methods.md

@@ -0,0 +1 @@
+* [#737](https://github.com/rubocop/rubocop-rails/issues/737): Fix a false positive for `Rails/DeprecatedActiveModelErrorsMethods` when using `keys` method with Rails 6.0. ([@koic][])

lib/rubocop/cop/rails/deprecated_active_model_errors_methods.rb

@@ -106,6 +106,8 @@ class DeprecatedActiveModelErrorsMethods < Base
 
         def on_send(node)
           any_manipulation?(node) do
+            next if node.method?(:keys) && target_rails_version <= 6.0
+
             add_offense(node) do |corrector|
               next unless AUTOCORECTABLE_METHODS.include?(node.method_name)
 

spec/rubocop/cop/rails/deprecated_active_model_errors_methods_spec.rb

@@ -37,28 +37,45 @@
       end
 
       context 'when using `keys` method' do
-        it 'registers and corrects an offense when root receiver is a variable' do
-          expect_offense(<<~RUBY, file_path)
-            user = create_user
-            user.errors.keys
-            ^^^^^^^^^^^^^^^^ Avoid manipulating ActiveModel errors as hash directly.
-          RUBY
-
-          expect_correction(<<~RUBY)
-            user = create_user
-            user.errors.attribute_names
-          RUBY
+        context 'Rails >= 6.1', :rails61 do
+          it 'registers and corrects an offense when root receiver is a variable' do
+            expect_offense(<<~RUBY, file_path)
+              user = create_user
+              user.errors.keys
+              ^^^^^^^^^^^^^^^^ Avoid manipulating ActiveModel errors as hash directly.
+            RUBY
+
+            expect_correction(<<~RUBY)
+              user = create_user
+              user.errors.attribute_names
+            RUBY
+          end
+
+          it 'registers and corrects an offense when root receiver is a method' do
+            expect_offense(<<~RUBY, file_path)
+              user.errors.keys.include?(:name)
+              ^^^^^^^^^^^^^^^^ Avoid manipulating ActiveModel errors as hash directly.
+            RUBY
+
+            expect_correction(<<~RUBY)
+              user.errors.attribute_names.include?(:name)
+            RUBY
+          end
         end
 
-        it 'registers and corrects an offense when root receiver is a method' do
-          expect_offense(<<~RUBY, file_path)
-            user.errors.keys.include?(:name)
-            ^^^^^^^^^^^^^^^^ Avoid manipulating ActiveModel errors as hash directly.
-          RUBY
-
-          expect_correction(<<~RUBY)
-            user.errors.attribute_names.include?(:name)
-          RUBY
+        context 'Rails <= 6.0', :rails60 do
+          it 'does not register an offense when root receiver is a variable' do
+            expect_no_offenses(<<~RUBY, file_path)
+              user = create_user
+              user.errors.keys
+            RUBY
+          end
+
+          it 'does not register an offense when root receiver is a method' do
+            expect_no_offenses(<<~RUBY, file_path)
+              user.errors.keys.include?(:name)
+            RUBY
+          end
         end
       end
     end