Fragment caching an erb template with a Phlex component complains it can't digest template

[davidalejandroaguilar]

Expected Behavior

Read fragment views/tests/index:06ce85b70ee7a70c70923bcbbff4dc2d/1693531182 (0.1ms)
Write fragment views/tests/index:06ce85b70ee7a70c70923bcbbff4dc2d/1693531182 (0.1ms)

Actual behavior

  Couldn't find template for digesting: news/new
Read fragment views/tests/index:06ce85b70ee7a70c70923bcbbff4dc2d/1693531182 (0.1ms)
Write fragment views/tests/index:06ce85b70ee7a70c70923bcbbff4dc2d/1693531182 (0.1ms)

How to reproduce

1. Enable dev caching

rails dev:cache

2. Add a component

class TestComponent < ApplicationComponent
  def template
    plain "hi"
  end
end

3. Render it within a Rails view

class TestsController < ApplicationController
  def index
  end
end

<%= cache Time.current.to_i do %>
  <%= render TestComponent.new %>
<% end %>

4. Refresh the page and check the logs

5. Modify the template

<%= cache Time.current.to_i do %>
  something new
  <%= render TestComponent.new %>
<% end %>

6. Refresh the page and check the logs

[joeldrapper]

Thanks for opening this as a separate issue. I’d like to try to fix this one, since compatibility with existing ERB is essential.

[joeldrapper]

@davidalejandroaguilar I’ve looked into this and confirmed the problem. It looks like Rails builds up a dependency tree by parsing the ERB files and finding render calls. It only does this when rendering partials.

For Phlex to fit in here, Rails would have to parse render calls to objects, e.g. render Foo.new and then establish an interface that the class can implement to be a part of the dependency tree.

Here’s a link to the current parser. https://github.com/rails/rails/blob/main/actionview/lib/action_view/render_parser/prism_render_parser.rb

We would be happy to implement a class method on our renderable classes if that was supported by Rails.

I think the best way forward is to bring this up in a new Rails issue. You can mention this issue and this one from ViewComponent. ViewComponent/view_component#234

For now, I’m going to close this as there’s nothing we can do here until something changes in Rails.