Check for existing persistent cache files on demand

[dwhelan]

When I was using puffing_billy I noticed that for the first request it did not check for a persisted cache file. Later, I realized that I was not calling Billy.proxy.restore_cache in my config and also did not notice the Billy.cache.load_dir method.

However, I had already written additional logic to check for a persisted cache entry on demand. And I think this may be an improvement for the existing approach for a few reasons:

• only requested cache files are read thus speeding up tests
• eliminates the need for Billy.proxy.restore_cache since cache files will be checked if the entry is not already in the memory cache
• clients do not need to worry about timing the invocation of Billy.proxy.restore_cache thus eliminating the 'race condition' noted in the readme file

[ronwsmith]

I've been using the changes in this pull request for several weeks and they works great! Thanks for doing this.

Thought I'd share another benefit I got out of lazy-loading the cache files. When authoring tests that dynamically hit external APIs, a lot of extra cache files can be created that you don't want in the codebase.

With the changes in this pull request, I was able to implement the following in my spec_helper.rb to delete any cache files not used when running the full test suite via DELETE_UNUSED_CACHE=true rake spec:features:

  config.after(:suite, type: :feature) do
    if ENV['DELETE_UNUSED_CACHE'] && defined?(Billy)
      puts "\n*** ALL UNUSED CACHE FILES WILL BE DELETED ***"
      local_cache_path = Rails.root.join(Billy.config.cache_path)
      used_cache_files = Billy.proxy.instance_variable_get(:@cache)

      Dir.glob(local_cache_path+'*.yml') do |full_filename|
        filename = full_filename.gsub(local_cache_path.to_s, '')
        unless used_cache_files[filename.gsub('.yml','')]
          puts " - DELETING #{filename}"
          File.delete(local_cache_path+filename)
        end
      end
    end
  end

[dwhelan]

@ronwsmith I'm glad you found the pull request useful. I like your deletion logic and I will try that out.

[oesmith]

Merged, thanks!

[dwhelan]

Thanks for merging this in!