Remove Redis 4.2 warnings.

[tgxworld]

Apps on Redis 4.2 and up will see a warning due to https://github.com/redis/redis-rb/commit/325752764995b02f17c3e5240ea489f641911d7d

[SamSaffron]

@casperisfine what should our approach be here.

Our dependency on redis is "weak" in that there is no explicit dependency. exists? may no exist in earlier redis gems.

Should we monkey patch it in and keep this code?

[tgxworld]

We can just implement exists? since it isn't hard. Essentially just calling @client.call([:exists, key])

[SamSaffron]

as long as it is backwards compatible with reasonable redis gem releases for whatever definition of reasonable that we can come up with

[tgxworld]

We're only using a single key so it should be backwards compatible all the way

[casperisfine]

Should we monkey patch it in and keep this code?

Yeah, based on your constraints I'd do this: https://github.com/MiniProfiler/rack-mini-profiler/commit/44dee3dc008e9addc1b029178980d1bc71be90f2

If the redis_store.rb file was autoloaded, you could go with a slightly cleaner alternative:

unless Redis.method_defined?(:exists?)
  module RedisExistsRefinement
    refine Redis do
      def exists?(key)
        exists(key)
      end
    end
  end
  using RedisExistsRefinement
end

[renchap]

Would it be possible to have a release that includes this PR? This is currently preventing our upgrade to the Redis 4.2 Thanks!

[SamSaffron]

@renchap sure, just pushed a release.

[renchap]

Amazing thanks!