From 770060d93a897cb5fb5108bb828b927fe6bb5353 Mon Sep 17 00:00:00 2001
From: Jean Boussier <jean.boussier@gmail.com>
Date: Mon, 14 Aug 2023 11:20:43 +0200
Subject: [PATCH] Handle non-string partial body in
 ActionView::CollectionCaching

Followup: https://github.com/rails/rails/pull/48645

Some template engines such as `jbuilder` use these Action View primitives
with types other than strings, which breaks a bunch of assumptions.

I wish I could add a test for this, but this is deep in private methods
I don't see a way to cover this.
---
 .../renderer/partial_renderer/collection_caching.rb   | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/actionview/lib/action_view/renderer/partial_renderer/collection_caching.rb b/actionview/lib/action_view/renderer/partial_renderer/collection_caching.rb
index d65d4c0cafaba..6ee720aa4896b 100644
--- a/actionview/lib/action_view/renderer/partial_renderer/collection_caching.rb
+++ b/actionview/lib/action_view/renderer/partial_renderer/collection_caching.rb
@@ -96,9 +96,16 @@ def fetch_or_cache_partial(cached_partials, template, order_by:)
             build_rendered_template(content, template)
           else
             rendered_partial = yield
-            if fragment = rendered_partial.body&.to_str
-              entries_to_write[cache_key] = fragment
+            body = rendered_partial.body
+
+            # We want to cache buffers as raw strings. This both improve performance and
+            # avoid creating forward compatibility issues with the internal representation
+            # of these two types.
+            if body.is_a?(ActionView::OutputBuffer) || body.is_a?(ActiveSupport::SafeBuffer)
+              body = body.to_str
             end
+
+            entries_to_write[cache_key] = body
             rendered_partial
           end
         end