From 2af83b3d128a869a046e7158c56a713776f0431a Mon Sep 17 00:00:00 2001
From: David Heinemeier Hansson <david@hey.com>
Date: Thu, 19 Dec 2024 17:44:21 -0800
Subject: [PATCH 1/2] Encapsulate stale_when_importmap_changes

---
 README.md                                       | 6 ++++--
 app/controllers/concerns/importmap/freshness.rb | 5 +++++
 lib/importmap/engine.rb                         | 7 +++++++
 3 files changed, 16 insertions(+), 2 deletions(-)
 create mode 100644 app/controllers/concerns/importmap/freshness.rb

diff --git a/README.md b/README.md
index f4c5bee..9828dcd 100644
--- a/README.md
+++ b/README.md
@@ -226,14 +226,16 @@ Import your module on the specific page. Note: you'll likely want to use a `cont
 
 ## Include a digest of the import map in your ETag
 
-If you're using [ETags](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/ETag) generated by Rails helpers like `stale?` or `fresh_when`, you need to include the digest of the import map into this calculation. Otherwise your application will return [304](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/304) cache responses even when your JavaScript assets have changed. You can avoid this with something like:
+If you're using [ETags](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/ETag) generated by Rails helpers like `stale?` or `fresh_when`, you need to include the digest of the import map into this calculation. Otherwise your application will return [304](https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/304) cache responses even when your JavaScript assets have changed. You can avoid this using the `stale_when_importmap_changes` method:
 
 ```ruby
 class ApplicationController < ActionController::Base
-  etag { Rails.application.importmap.digest(resolver: helpers) if request.format&.html? }
+  stale_when_importmap_changes
 end
 ```
 
+This will add the digest of the importmap to the etag calculation when the request format is HTML.
+
 
 ## Sweeping the cache in development and test
 
diff --git a/app/controllers/concerns/importmap/freshness.rb b/app/controllers/concerns/importmap/freshness.rb
new file mode 100644
index 0000000..0820a2f
--- /dev/null
+++ b/app/controllers/concerns/importmap/freshness.rb
@@ -0,0 +1,5 @@
+module Importmap::Freshness
+  def stale_when_importmap_changes
+    etag { Rails.application.importmap.digest(resolver: helpers) if request.format&.html? }
+  end
+end
diff --git a/lib/importmap/engine.rb b/lib/importmap/engine.rb
index 1c823f4..83e7471 100755
--- a/lib/importmap/engine.rb
+++ b/lib/importmap/engine.rb
@@ -48,6 +48,13 @@ class Engine < ::Rails::Engine
       end
     end
 
+    initializer "importmap.concerns" do
+      ActiveSupport.on_load(:action_controller_base) do
+        require_relative "../../app/controllers/concerns/importmap/freshness"
+        extend Importmap::Freshness
+      end
+    end
+
     initializer "importmap.helpers" do
       ActiveSupport.on_load(:action_controller_base) do
         helper Importmap::ImportmapTagsHelper

From df856d065435952e4842f4da46ea00a1766b859e Mon Sep 17 00:00:00 2001
From: David Heinemeier Hansson <david@hey.com>
Date: Fri, 20 Dec 2024 17:01:35 -0800
Subject: [PATCH 2/2] Use autoload instead of relative require

---
 app/controllers/{concerns => }/importmap/freshness.rb | 0
 lib/importmap/engine.rb                               | 3 +--
 2 files changed, 1 insertion(+), 2 deletions(-)
 rename app/controllers/{concerns => }/importmap/freshness.rb (100%)

diff --git a/app/controllers/concerns/importmap/freshness.rb b/app/controllers/importmap/freshness.rb
similarity index 100%
rename from app/controllers/concerns/importmap/freshness.rb
rename to app/controllers/importmap/freshness.rb
diff --git a/lib/importmap/engine.rb b/lib/importmap/engine.rb
index 83e7471..337c7fe 100755
--- a/lib/importmap/engine.rb
+++ b/lib/importmap/engine.rb
@@ -11,7 +11,7 @@ class Engine < ::Rails::Engine
     config.importmap.cache_sweepers = []
     config.importmap.rescuable_asset_errors = []
 
-    config.autoload_once_paths = %W( #{root}/app/helpers )
+    config.autoload_once_paths = %W( #{root}/app/helpers #{root}/app/controllers )
 
     initializer "importmap" do |app|
       app.importmap = Importmap::Map.new
@@ -50,7 +50,6 @@ class Engine < ::Rails::Engine
 
     initializer "importmap.concerns" do
       ActiveSupport.on_load(:action_controller_base) do
-        require_relative "../../app/controllers/concerns/importmap/freshness"
         extend Importmap::Freshness
       end
     end