fixed false positive ActionControllerFlashBefore after rescue

Co-Authored-By: Koichi ITO <koic.ito@gmail.com>

changelog/fix_false_positive_action_controller_flash_before_render_after_rescue.md

@@ -0,0 +1 @@
+* [#881](https://github.com/rubocop/rubocop-rails/pull/881): Fix a false positive for `Rails/ActionControllerFlashBeforeRender` when using `flash` in multiline `rescue` branch before `redirect_to`. ([@gurix][])

lib/rubocop/cop/rails/action_controller_flash_before_render.rb

@@ -69,8 +69,8 @@ def on_send(flash_node)
  def followed_by_render?(flash_node)
  flash_assigment_node = find_ancestor(flash_node, type: :send)
  context = flash_assigment_node
- if (if_node = context.each_ancestor(:if).first)
- context = if_node
+ if (ancestor_node = context.each_ancestor(:if, :rescue).first)
+ context = ancestor_node
  elsif context.right_siblings.empty?
  return true
  end

spec/rubocop/cop/rails/action_controller_flash_before_render_spec.rb

@@ -201,6 +201,23 @@ def create
  end
  RUBY
  end
+
+ it 'does not register an offense when using `flash` in multiline `rescue` branch before `redirect_to`' do
+ expect_no_offenses(<<~RUBY)
+ class HomeController < #{parent_class}
+ def create
+ begin
+ do_something
+ flash[:alert] = "msg in begin"
+ rescue
+ flash[:alert] = "msg in rescue"
+ end
+
+ redirect_to :index
+ end
+ end
+ RUBY
+ end
  end
  end