Merge pull request rubocop#840 from koic/fix_a_false_positive_for_rails_action_controller_flash_before_render

[Fix rubocop#825] Fix a false positive for `Rails/ActionControllerFlashBeforeRender`

Author: koic

changelog/fix_a_false_positive_for_rails_action_controller_flash_before_render.md

@@ -0,0 +1 @@
+* [#825](https://github.com/rubocop/rubocop-rails/issues/825): Fix a false positive for `Rails/ActionControllerFlashBeforeRender` when using condition before `redirect_to`. ([@koic][])

lib/rubocop/cop/rails/action_controller_flash_before_render.rb

@@ -37,8 +37,8 @@ class ActionControllerFlashBeforeRender < Base
           ^(send (send nil? :flash) :[]= ...)
         PATTERN
 
-        def_node_search :redirect_to?, <<~PATTERN
-          (send nil? :redirect_to ...)
+        def_node_search :render?, <<~PATTERN
+          (send nil? :render ...)
         PATTERN
 
         def_node_search :action_controller?, <<~PATTERN
@@ -53,7 +53,7 @@ class ActionControllerFlashBeforeRender < Base
         def on_send(flash_node)
           return unless flash_assignment?(flash_node)
 
-          return if followed_by_redirect_to?(flash_node)
+          return unless followed_by_render?(flash_node)
 
           return unless instance_method_or_block?(flash_node)
 
@@ -66,13 +66,15 @@ def on_send(flash_node)
 
         private
 
-        def followed_by_redirect_to?(flash_node)
+        def followed_by_render?(flash_node)
           flash_assigment_node = find_ancestor(flash_node, type: :send)
-          context = flash_assigment_node.parent
+          context = flash_assigment_node
+          context = context.parent if context.parent.if_type?
+          context = context.right_siblings
+          return true if context.empty?
 
-          flash_index = context.children.index(flash_assigment_node)
-          context.each_child_node.with_index.any? do |node, index|
-            index > flash_index && redirect_to?(node)
+          context.compact.any? do |node|
+            render?(node)
           end
         end
 

spec/rubocop/cop/rails/action_controller_flash_before_render_spec.rb

@@ -104,7 +104,7 @@ class NonController < ApplicationRecord
     context 'with a condition' do
       %w[ActionController::Base ApplicationController].each do |parent_class|
         context "within a class inherited from #{parent_class}" do
-          it 'registers an offense and corrects' do
+          it 'registers an offense and corrects when using `flash` before `render`' do
             expect_offense(<<~RUBY)
               class HomeController < #{parent_class}
                 def create
@@ -124,6 +124,34 @@ def create
               end
             RUBY
           end
+
+          it 'does not register an offense when using `flash` before `redirect_to`' do
+            expect_no_offenses(<<~RUBY)
+              class HomeController < #{parent_class}
+                def create
+                  if condition
+                    flash[:alert] = "msg"
+                  end
+
+                  redirect_to :index
+                end
+              end
+            RUBY
+          end
+
+          it 'does not register an offense when using `flash` before `redirect_back`' do
+            expect_no_offenses(<<~RUBY)
+              class HomeController < #{parent_class}
+                def create
+                  if condition
+                    flash[:alert] = "msg"
+                  end
+
+                  redirect_back fallback_location: root_path
+                end
+              end
+            RUBY
+          end
         end
       end