Fix digesting templates with mixed formats

[javan]

Fixes #28503
Follow up to: #25411

[thomasfedb]

I've tested this against the repro I created when I reported #28503 and this PR resolves the issue. I've been unable to immediately test this against the production app where I first noticed this issue as the app doesn't play nice with rails master presently. Hopefully this can be backported against 5.1 and 5.2 - which I'm happy to help with.

[thomasfedb]

Having now backported the fix to 5.1 stable I can confirm that this fixes the issue I was experiencing.

[kaspth]

Nice! Feel free to backport to 5-2-stable and 5-1-stable.

[javan]

I think I've found a better solution that aligns more closely with the behavior of rendering: 052a6d5

By setting finder.formats, we avoid the need to find with a :formats option. And when it's set to [:js], we automatically get an :html fallback:

rails/actionview/lib/action_view/lookup_context.rb

Lines 245 to 255 in d9736e5

	# add :html as fallback to :js.
	def formats=(values)
	if values
	values.concat(default_formats) if values.delete "*/*".freeze
	if values == [:js]
	values << :html
	@html_fallback_for_js = true
	end
	end
	super(values)
	end

Rendering a request works similarly:

rails/actionview/lib/action_view/rendering.rb

Lines 106 to 111 in d9736e5

	# Assign the rendered format to look up context.
	def _process_format(format)
	super
	lookup_context.formats = [format.to_sym]
	lookup_context.rendered_format = lookup_context.formats.first
	end

@thomasfedb, mind trying once more with my latest commit? If it doesn't pan out I'll use my first approach.

@kaspth, if you have any other ideas, please do let me know! It's a jungle in there.

[thomasfedb]

@javan would that break if I, for example, tried to render a .txt partial inside a .js partial? Or some other cross-format combination?

[javan]

I think that will work, but please do investigate.

[thomasfedb]

@javan I'll give it a try

[thomasfedb]

@javan new fix definitely solves the issue when using HTML partials inside JS views as with the previous fix.

There is an issue, however, when you render a partial with a particular format, e.g. partial: 'partial2', formats: :text, collection: [1], cached: true which results in a Couldn't find template for digesting: home/_partial2 message, and a blank cache key is used (and therefore old cache is still used when partial is updated).

[thomasfedb]

The above happens inside both JS and HTML views, as you'd expect.

[thomasfedb]

Sorry, should make it clear that this issue with rendering with specified format appears only to occur with the new fix, and was not a problem with the initial fix.

With initial fix:

Processing by HomeController#index as HTML
  Rendering home/index.html.erb within layouts/application
Read fragment views/home/_partial2:140b891b4a188473f1a3d632568d6824/localhost:3000/ (0.0ms)
Write fragment views/home/_partial2:140b891b4a188473f1a3d632568d6824/localhost:3000/ (0.0ms)
  Rendered collection of home/_partial2.text.erb [0 / 1 cache hits] (1.8ms)
  Rendered home/index.html.erb within layouts/application (14.6ms)
Completed 200 OK in 1053ms (Views: 1051.9ms | ActiveRecord: 0.0ms)

With new fix:

Processing by HomeController#index as HTML
  Rendering home/index.html.erb within layouts/application
  Couldn't find template for digesting: home/_partial2
Read fragment views/home/_partial2/localhost:3000/ (0.1ms)
Write fragment views/home/_partial2/localhost:3000/ (0.1ms)
  Rendered collection of home/_partial2.text.erb [0 / 1 cache hits] (1.6ms)
  Rendered home/index.html.erb within layouts/application (14.4ms)
Completed 200 OK in 1037ms (Views: 1036.6ms | ActiveRecord: 0.0ms)

Let me know if you need further info @javan

[javan]

Thanks @thomasfedb! It looks like DependencyTracker doesn't parse the :formats option currently. So my initial fix happens to work correctly, but would probably fail if you had more than one _partial2 template. If you had _partial2.text.erb and _partial2.html.erb it would always digest the html template.

[thomasfedb]

@javan right, there was only _partial2.text.erb in my test, no other partial called partial2. I'd be happy to go with either of your fixes for now, what do you think?

[javan]

Went with the 2nd approach. Thanks for all your help @thomasfedb!

[javan]

Backported to 5-2 0b53f57 and 5-1 eb30975

[thomasfedb]

Thanks @javan, and clue as to when the next 5.1.x will be cut?

[javan]

I'm not sure about the 5-1 release schedule. Maybe @rafaelfranca knows? You can always point your Gemfile at the Rails branch or sha.

[thomasfedb]

Using the branch now in dev, but would prefer to have an official release before I deploy to prod.

[rafaelfranca]

It may takes months. We usually release every 6 weeks, but given 5.2 is going to be the official release, it may take more time.