[Fix rubocop#12237] Fix an error for Style/NestedTernaryOperator

Fixes rubocop#12237.

This PR fixes an error for `Style/NestedTernaryOperator`
when a ternary operator has a nested ternary operator within an `if`.

changelog/fix_an_error_for_style_nested_ternary_operator.md

@@ -0,0 +1 @@
+* [#12237](https://github.com/rubocop/rubocop/issues/12237): Fix an error for `Style/NestedTernaryOperator` when a ternary operator has a nested ternary operator within an `if`. ([@koic][])

lib/rubocop/cop/style/nested_ternary_operator.rb

@@ -27,24 +27,16 @@ def on_if(node)
 
           node.each_descendant(:if).select(&:ternary?).each do |nested_ternary|
             add_offense(nested_ternary) do |corrector|
-              if_node = if_node(nested_ternary)
-              next if part_of_ignored_node?(if_node)
+              next if part_of_ignored_node?(node)
 
-              autocorrect(corrector, if_node)
-              ignore_node(if_node)
+              autocorrect(corrector, node)
+              ignore_node(node)
             end
           end
         end
 
         private
 
-        def if_node(node)
-          node = node.parent
-          return node if node.if_type?
-
-          if_node(node)
-        end
-
         def autocorrect(corrector, if_node)
           replace_loc_and_whitespace(corrector, if_node.loc.question, "\n")
           replace_loc_and_whitespace(corrector, if_node.loc.colon, "\nelse\n")

spec/rubocop/cop/style/nested_ternary_operator_spec.rb

@@ -47,6 +47,29 @@
     RUBY
   end
 
+  it 'registers an offense when a ternary operator has a nested ternary operator within an `if`' do
+    expect_offense(<<~RUBY)
+      a ? (
+        if b
+          c ? 1 : 2
+          ^^^^^^^^^ Ternary operators must not be nested. Prefer `if` or `else` constructs instead.
+        end
+      ) : 3
+    RUBY
+
+    expect_correction(<<~RUBY)
+      if a
+
+        if b
+          c ? 1 : 2
+        end
+
+      else
+      3
+      end
+    RUBY
+  end
+
   it 'accepts a non-nested ternary operator within an if' do
     expect_no_offenses(<<~RUBY)
       a = if x