Include the content of the flash in the auto-generated etag (#26250)

Include the content of the flash in the auto-generated etag

3 files changed, 18 insertions, 0 deletions

diff --git a/actionpack/lib/action_controller.rb b/actionpack/lib/action_controller.rb
index fc86a907b3..50f20aa789 100644
--- a/actionpack/lib/action_controller.rb
+++ b/actionpack/lib/action_controller.rb
@@ -23,6 +23,7 @@ module ActionController
     autoload :Cookies
     autoload :DataStreaming
     autoload :EtagWithTemplateDigest
+    autoload :EtagWithFlash
     autoload :Flash
     autoload :ForceSSL
     autoload :Head
diff --git a/actionpack/lib/action_controller/base.rb b/actionpack/lib/action_controller/base.rb
index 68a526eccb..ca8066cd82 100644
--- a/actionpack/lib/action_controller/base.rb
+++ b/actionpack/lib/action_controller/base.rb
@@ -213,6 +213,7 @@ module ActionController
       Renderers::All,
       ConditionalGet,
       EtagWithTemplateDigest,
+      EtagWithFlash,
       Caching,
       MimeResponds,
       ImplicitRender,
diff --git a/actionpack/lib/action_controller/metal/etag_with_flash.rb b/actionpack/lib/action_controller/metal/etag_with_flash.rb
new file mode 100644
index 0000000000..474d75f02e
--- /dev/null
+++ b/actionpack/lib/action_controller/metal/etag_with_flash.rb
@@ -0,0 +1,16 @@
+module ActionController
+  # When you're using the flash, it's generally used as a conditional on the view.
+  # This means the content of the view depends on the flash. Which in turn means
+  # that the etag for a response should be computed with the content of the flash
+  # in mind. This does that by including the content of the flash as a component
+  # in the etag that's generated for a response.
+  module EtagWithFlash
+    extend ActiveSupport::Concern
+
+    include ActionController::ConditionalGet
+
+    included do
+      etag { flash unless flash.empty? }
+    end
+  end
+end