[Fix #9050] Fix a false positive for Style/NegatedIfElseCondition

changelog/fix_false_negative_for_negated_if_else_condition.md

@@ -0,0 +1 @@
+* [#9050](https://github.com/rubocop-hq/rubocop/issues/9050): Fix a false positive for `Style/NegatedIfElseCondition` when `if` with `!!` condition. ([@koic][])

lib/rubocop/cop/style/negated_if_else_condition.rb

@@ -35,6 +35,8 @@ class NegatedIfElseCondition < Base
 
         NEGATED_EQUALITY_METHODS = %i[!= !~].freeze
 
+        def_node_matcher :double_negation?, '(send (send _ :!) :!)'
+
         def self.autocorrect_incompatible_with
           [Style::InverseMethods, Style::Not]
         end
@@ -47,7 +49,7 @@ def on_if(node)
           return unless if_else?(node)
 
           condition = node.condition
-          return unless negated_condition?(condition)
+          return if double_negation?(condition) || !negated_condition?(condition)
 
           type = node.ternary? ? 'ternary' : 'if-else'
           add_offense(node, message: format(MSG, type: type)) do |corrector|

spec/rubocop/cop/style/negated_if_else_condition_spec.rb

@@ -153,6 +153,16 @@
     RUBY
   end
 
+  it 'does not register an offense when `if` with `!!` condition' do
+    expect_no_offenses(<<~RUBY)
+      if !!x
+        do_something
+      else
+        do_another_thing
+      end
+    RUBY
+  end
+
   it 'does not register an offense when `if` with negated condition has no `else` branch' do
     expect_no_offenses(<<~RUBY)
       if !x