1 files changed, 49 insertions, 0 deletions
diff --git a/actionview/lib/action_view/cache_expiry.rb b/actionview/lib/action_view/cache_expiry.rb
new file mode 100644
index 0000000000..820afc093d
--- /dev/null
+++ b/actionview/lib/action_view/cache_expiry.rb
@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+module ActionView
+  class CacheExpiry
+    class Executor
+      def initialize(watcher:)
+        @cache_expiry = CacheExpiry.new(watcher: watcher)
+      end
+
+      def before(target)
+        @cache_expiry.clear_cache_if_necessary
+      end
+    end
+
+    def initialize(watcher:)
+      @watched_dirs = nil
+      @watcher_class = watcher
+      @watcher = nil
+    end
+
+    def clear_cache_if_necessary
+      watched_dirs = dirs_to_watch
+      if watched_dirs != @watched_dirs
+        @watched_dirs = watched_dirs
+        @watcher = @watcher_class.new([], watched_dirs) do
+          clear_cache
+        end
+        @watcher.execute
+      else
+        @watcher.execute_if_updated
+      end
+    end
+
+    def clear_cache
+      ActionView::LookupContext::DetailsKey.clear
+    end
+
+    private
+
+      def dirs_to_watch
+        fs_paths = all_view_paths.grep(FileSystemResolver)
+        fs_paths.map(&:path).sort.uniq
+      end
+
+      def all_view_paths
+        ActionView::ViewPaths.all_view_paths.flat_map(&:paths)
+      end
+  end
+end