[Fix rubocop#8864] Fix false positive for Style/RedundantBegin with…

… a postfix `while` or `until`

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Bug fixes
 
 * [#8782](https://github.com/rubocop-hq/rubocop/issues/8782): Fix incorrect autocorrection for `Style/TernaryParentheses` with `defined?`. ([@dvandersluis][])
+* [#8864](https://github.com/rubocop-hq/rubocop/issues/8864): Fix false positive for `Style/RedundantBegin` with a postfix `while` or `until`. ([@dvandersluis][])
 
 ## 0.93.0 (2020-10-08)
 

lib/rubocop/cop/style/redundant_begin.rb

@@ -86,6 +86,7 @@ def on_block(node)
 
         def on_kwbegin(node)
           return if node.parent&.assignment?
+          return if node.parent&.post_condition_loop?
 
           first_child = node.children.first
           return if first_child.rescue_type? || first_child.ensure_type?

spec/rubocop/cop/style/redundant_begin_spec.rb

@@ -204,6 +204,24 @@ def method
     RUBY
   end
 
+  it 'does not register an offense when using `begin` with `while`' do
+    expect_no_offenses(<<~RUBY)
+      begin
+        do_first_thing
+        some_value = do_second_thing
+      end while some_value
+    RUBY
+  end
+
+  it 'does not register an offense when using `begin` with `until`' do
+    expect_no_offenses(<<~RUBY)
+      begin
+        do_first_thing
+        some_value = do_second_thing
+      end until some_value
+    RUBY
+  end
+
   context '< Ruby 2.5', :ruby24 do
     it 'accepts a do-end block with a begin-end' do
       expect_no_offenses(<<~RUBY)