Cache regex in template OptimizedFileSystemResolver

[jhawthorn]

This is a follow up to #33860, which made templates faster by doing more work in ruby to reduce I/O. This PR reduces the amount of work we're doing in ruby. Like the previous PR this will mostly benefit startup time and development mode (where Resolver.caching is false).

Previously we were building a regex for each call to #query (which is called for each view_path on each search). Instead, this PR creates a regex for just the details component of the path (which itself is slightly faster), and caches that regex.

A regex used to look like:

/\A\/Users\/jhawthorn\/src\/rails\/railties\/lib\/rails\/templates\/rails\/welcome\/index(\.(?<locale>en))?(\.(?<formats>html|text|js|css|ics|csv|vcf|vtt|png|jpeg|gif|bmp|tiff|svg|mpeg|mp3|ogg|m4a|webm|mp4|otf|ttf|woff|woff2|xml|rss|atom|yaml|multipart_form|url_encoded_form|json|pdf|zip|gzip))?(\+(?<variants>))?(\.(?<handlers>raw|erb|html|builder|ruby))?\z/

Now looks like:

/\A\(\.(?<locale>en))?(\.(?<formats>html|text|js|css|ics|csv|vcf|vtt|png|jpeg|gif|bmp|tiff|svg|mpeg|mp3|ogg|m4a|webm|mp4|otf|ttf|woff|woff2|xml|rss|atom|yaml|multipart_form|url_encoded_form|json|pdf|zip|gzip))?(\+(?<variants>))?(\.(?<handlers>raw|erb|html|builder|ruby))?\z/

Benchmark

The speedup depends a lot on how slow the globs are. Listing directories on my Linux machine is way faster than on my MacBook 🤔. On my MacBook it's still ~1.5x faster 🎉

Benchmark:

require "benchmark/ips"
require "action_view"
require "action_pack"
require "action_controller"

class TestController < ActionController::Base
end

ActionView::Resolver.caching = false
TestController.view_paths = [File.expand_path("./railties/lib/rails/templates")]
context = TestController.new.lookup_context

Benchmark.ips do |x|
  x.report("template") do
    context.find_template("rails/welcome/index", [], false, {}, {})
  end
end

Before:

Warming up --------------------------------------
            template   387.000  i/100ms
Calculating -------------------------------------
            template      3.821k (± 5.0%) i/s -     19.350k in   5.078706s

After:

Warming up --------------------------------------
            template   586.000  i/100ms
Calculating -------------------------------------
            template      5.717k (± 7.3%) i/s -     28.714k in   5.055056s

cc @tenderlove @eileencodes

[matthewd]

Is it safe to use details directly as a cache key here? Nearby we have a separate details_key thingy.

Does it only contain entries for EXTENSIONS.keys? (And are they immutable?)

The biggest thing that I default to worrying about inside caches is reloading -- but as long as those four are the only things in there, that seems fine.

After that the next concern is user-supplied data: I think we might have a bigger issue with that one. Can I add an entry to this permanent cache by e.g. tacking ?format=foo onto an arbitrary URL?

[jhawthorn]

I think I'll take a different approach with this. I'm hoping to use the same regex for parsing regardless of details.