turbo_stream helpers not capturing correctly

[boardfish]

I'm trying to update multiple parts of the page by rendering a component that uses multiple turbo_stream.update tags. This comes out mangled, with a subset of the expected HTML rendered followed by several empty turbo-stream tags. I'll put together a failing test case soon.

Steps to reproduce

1. Create a component whose template renders turbo-stream tags using the helper provided by turbo-rails.
2. Render this in a controller action as follows:

respond_to { |format| format.turbo_stream { render ExampleComponent.new } }

Expected behavior

The content given to each use of the turbo_stream.update helper should be rendered inside turbo-stream tags.

Actual behavior

Some content is captured and rendered before empty turbo-stream tags.

System configuration

Rails version: 7.0.0.alpha2

Ruby version: 2.7.4

Gem version: 2.40.0

[boardfish]

I think this could be resolved by using a single output buffer if we come to do it again. In the meantime, this might work since it's akin to rendering a component in a controller context.