1 files changed, 39 insertions, 0 deletions
diff --git a/actionpack/lib/action_dispatch/middleware/actionable_exceptions.rb b/actionpack/lib/action_dispatch/middleware/actionable_exceptions.rb
new file mode 100644
index 0000000000..e94cc46603
--- /dev/null
+++ b/actionpack/lib/action_dispatch/middleware/actionable_exceptions.rb
@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+require "erb"
+require "action_dispatch/http/request"
+require "active_support/actionable_error"
+
+module ActionDispatch
+  class ActionableExceptions # :nodoc:
+    cattr_accessor :endpoint, default: "/rails/actions"
+
+    def initialize(app)
+      @app = app
+    end
+
+    def call(env)
+      request = ActionDispatch::Request.new(env)
+      return @app.call(env) unless actionable_request?(request)
+
+      ActiveSupport::ActionableError.dispatch(request.params[:error].to_s.safe_constantize, request.params[:action])
+
+      redirect_to request.params[:location]
+    end
+
+    private
+      def actionable_request?(request)
+        request.show_exceptions? && request.post? && request.path == endpoint
+      end
+
+      def redirect_to(location)
+        body = "<html><body>You are being <a href=\"#{ERB::Util.unwrapped_html_escape(location)}\">redirected</a>.</body></html>"
+
+        [302, {
+          "Content-Type" => "text/html; charset=#{Response.default_charset}",
+          "Content-Length" => body.bytesize.to_s,
+          "Location" => location,
+        }, [body]]
+      end
+  end
+end