[Fix rubocop#10926] Make Style/SafeNavigation aware of a redundant …

…nil check

Fixes rubocop#10926.

This PR makes `Style/SafeNavigation` aware of a redundant nil check.

IMHO, the context of this patch is a minimal update.
OTOH, a new cop like `Style/RedundantNilCheck` cop may be implemented
if it is not suitable for this `Style/SafeNavigation` cop.
(But I'm not sure if it's the best.)

changelog/fix_make_style_safe_navigation_aware_of_a_redundant_nil_check.md

@@ -0,0 +1 @@
+* [#10926](https://github.com/rubocop/rubocop/issues/10926): Make `Style/SafeNavigation` aware of a redundant nil check. ([@koic][])

lib/rubocop/cop/style/safe_navigation.rb

@@ -123,7 +123,7 @@ def check_node(node)
           return unless receiver == checked_variable
           return if use_var_only_in_unless_modifier?(node, checked_variable)
           return if chain_length(method_chain, method) > max_chain_length
-          return if unsafe_method_used?(method_chain, method)
+          return if unsafe_method_used?(method_chain, method) && !method.safe_navigation?
           return if method_chain.method?(:empty?)
 
           add_offense(node) { |corrector| autocorrect(corrector, node) }
@@ -141,7 +141,7 @@ def autocorrect(corrector, node)
 
           corrector.remove(begin_range(node, body))
           corrector.remove(end_range(node, body))
-          corrector.insert_before(method_call.loc.dot, '&')
+          corrector.insert_before(method_call.loc.dot, '&') unless method_call.safe_navigation?
           handle_comments(corrector, node, method_call)
 
           add_safe_nav_to_all_methods_in_chain(corrector, method_call, body)

spec/rubocop/cop/style/safe_navigation_spec.rb

@@ -205,6 +205,17 @@
         RUBY
       end
 
+      it 'registers an offense when safe guard check and safe navigation method call are connected with `&&` condition' do
+        expect_offense(<<~RUBY, variable: variable)
+          %{variable} && %{variable}&.do_something
+          ^{variable}^^^^^{variable}^^^^^^^^^^^^^^ Use safe navigation (`&.`) instead of checking if an object exists before calling the method.
+        RUBY
+
+        expect_correction(<<~RUBY)
+          #{variable}&.do_something
+        RUBY
+      end
+
       it 'registers an offense for a method call on an accessor ' \
          'safeguarded by a check for the accessed variable' do
         expect_offense(<<~RUBY, variable: variable)