From ca7c820c6962788d510c99a68e725de83cbe9cad Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ricardo=20D=C3=ADaz?= <ricardotk002@gmail.com>
Date: Tue, 18 May 2021 21:26:24 -0500
Subject: [PATCH] Remove `ActionDispatch::Flash::NullFlash`

After #42167, all apps (except api only ones) have access to the flash
module. If the session store is disabled, then an empty flash object
is used.

This patch also prevents the flash from being committed to the session
if this is not enabled.
---
 .../metal/request_forgery_protection.rb       |  4 ++++
 actionpack/lib/action_controller/test_case.rb |  4 ++++
 .../lib/action_dispatch/middleware/flash.rb   | 21 ++-----------------
 actionpack/test/controller/flash_test.rb      |  2 +-
 4 files changed, 11 insertions(+), 20 deletions(-)

diff --git a/actionpack/lib/action_controller/metal/request_forgery_protection.rb b/actionpack/lib/action_controller/metal/request_forgery_protection.rb
index 1e505a9576..d6ececb3f6 100644
--- a/actionpack/lib/action_controller/metal/request_forgery_protection.rb
+++ b/actionpack/lib/action_controller/metal/request_forgery_protection.rb
@@ -199,6 +199,10 @@ module ActionController #:nodoc:
             def exists?
               true
             end
+
+            def enabled?
+              false
+            end
           end
 
           class NullCookieJar < ActionDispatch::Cookies::CookieJar #:nodoc:
diff --git a/actionpack/lib/action_controller/test_case.rb b/actionpack/lib/action_controller/test_case.rb
index 87d2791ec8..7c9221e2ce 100644
--- a/actionpack/lib/action_controller/test_case.rb
+++ b/actionpack/lib/action_controller/test_case.rb
@@ -211,6 +211,10 @@ module ActionController
       @data.fetch(key.to_s, *args, &block)
     end
 
+    def enabled?
+      true
+    end
+
     private
       def load!
         @id
diff --git a/actionpack/lib/action_dispatch/middleware/flash.rb b/actionpack/lib/action_dispatch/middleware/flash.rb
index a3be2daa05..d0efda70aa 100644
--- a/actionpack/lib/action_dispatch/middleware/flash.rb
+++ b/actionpack/lib/action_dispatch/middleware/flash.rb
@@ -45,7 +45,6 @@ module ActionDispatch
       # read a notice you put there or <tt>flash["notice"] = "hello"</tt>
       # to put a new one.
       def flash
-        return Flash::NullFlash unless session.respond_to?(:loaded?)
         flash = flash_hash
         return flash if flash
         self.flash = Flash::FlashHash.from_session_value(session["flash"])
@@ -60,16 +59,14 @@ module ActionDispatch
       end
 
       def commit_flash # :nodoc:
-        session    = self.session || {}
-        flash_hash = self.flash_hash
+        return unless session.enabled?
 
         if flash_hash && (flash_hash.present? || session.key?("flash"))
           session["flash"] = flash_hash.to_session_value
           self.flash = flash_hash.dup
         end
 
-        if (!session.respond_to?(:loaded?) || session.loaded?) && # reset_session uses {}, which doesn't implement #loaded?
-            session.key?("flash") && session["flash"].nil?
+        if session.loaded? && session.key?("flash") && session["flash"].nil?
           session.delete("flash")
         end
       end
@@ -80,20 +77,6 @@ module ActionDispatch
       end
     end
 
-    module NullFlash #:nodoc:
-      class << self
-        def []=(k, v); end
-
-        def [](k); end
-
-        def alert=(message); end
-
-        def notice=(message); end
-
-        def empty?; end
-      end
-    end
-
     class FlashNow #:nodoc:
       attr_accessor :flash
 
diff --git a/actionpack/test/controller/flash_test.rb b/actionpack/test/controller/flash_test.rb
index 3f81094d96..d73371eb95 100644
--- a/actionpack/test/controller/flash_test.rb
+++ b/actionpack/test/controller/flash_test.rb
@@ -244,7 +244,7 @@ class FlashIntegrationTest < ActionDispatch::IntegrationTest
   SessionKey = "_myapp_session"
   Generator = ActiveSupport::CachingKeyGenerator.new(
     ActiveSupport::KeyGenerator.new("b3c631c314c0bbca50c1b2843150fe33", iterations: 1000)
- )
+  )
   Rotations = ActiveSupport::Messages::RotationConfiguration.new
   SIGNED_COOKIE_SALT = "signed cookie"