Caching in Rails throws an exception by default

[bradgessler]

While I was shooting the caching unit for the Phlex on Rails course, I was surprised about the behavior of the cache.

Here's the commit where I discovered the issue: thingybase/server@c9a416f

To recreate, spin up a Rails app, use cache in any Phlex component in Rails, then run rails dev:cache to enable the cache. You'll get an exception from this block:

	# Override this method to use a different cache store.
	private def cache_store
		raise "Cache store not implemented."
	end

This surprised me for a few reasons.

1. I assumed from the docs Phlex caching in Rails would use the in-memory FIFO store (https://www.phlex.fun/components/caching.html)
2. When I enabled the cache, I was surprised to see the exception message.

I think a reasonable behavior, in terms of "least surprises", is to add this into Components::Base by default, or equivalent.

class Components::Base
  def cache_store
    Rails.cache
  end
end

Additionally, I don't think this is implemented correctly in phlex-rails

	def low_level_cache(...)
		Rails.application.config.action_controller.perform_caching ? super : yield
	end

I get that this "disables caching", but I think the correct behavior would be to delegate this to Rails's cache store and let it handle what to do when a value is disabled or enabled.

I ran into this problem when I was trying to diagnose an issue with my cache not working that ended up not being a bug (I enabled cache for a different Raisl project 🤣)

What I'd propose for the "fix" is something like this:

1. Delete the low_level_cache method in phlex-rails and let cache_store handle no-ops.
2. Either patch cache_store in the phlex-rails gem to include Rails.cache (principle of least surprise) or include it in the generator.

I can put all of this into a PR, but wanted to check on here first to make sure I'm not overlooking some sort of default behavior.

[joeldrapper]

I agree we should probably pre-define the cache store pointing to your rails cache store.

We could do it in the generated code as you suggested to make it transparent.

When it comes to enabling/disabling the cache, we wanted to make that setting apply not only to the Rails cache store but also to any other cache store you configured, such as our FIFO cache store.

Especially as that could be used by a library that only depends on Phlex, while the rest of your app might use a different cache store.

We could make our FIFO cache store noop when it sees this config, but that would mean making a version of that cache store just for Rails. It seemed better to make the Rails adapter skip talking to the cache store altogether.

[bradgessler]

I opened a PR with the easy fix.