[Fix #10760] Fix a false positive for Lint/NonAtomicFileOperation

changelog/fix_a_false_positive_for_non_atomic_file_operation.md

@@ -0,0 +1 @@
+* [#10760](https://github.com/rubocop/rubocop/issues/10760): Fix a false positive for `Lint/NonAtomicFileOperation` when using `FileTest.exist?` with `if` condition that has `else` branch. ([@koic][])

lib/rubocop/cop/lint/non_atomic_file_operation.rb

@@ -72,6 +72,7 @@ class NonAtomicFileOperation < Base
 
         def on_send(node)
           return unless node.parent&.if_type?
+          return if node.parent.else_branch
           return if explicit_not_force?(node)
           return unless (exist_node = send_exist_node(node.parent).first)
           return unless exist_node.first_argument == node.first_argument

spec/rubocop/cop/lint/non_atomic_file_operation_spec.rb

@@ -173,4 +173,14 @@
       end
     RUBY
   end
+
+  it 'does not register an offense when using `FileTest.exist?` with `if` condition that has `else` branch' do
+    expect_no_offenses(<<~RUBY)
+      if FileTest.exist?(path)
+        FileUtils.mkdir(path)
+      else
+        do_something
+      end
+    RUBY
+  end
 end