Deprecate == and != from Redis::Future

[GustavoCaso]

For more information please check #875

Most developers when using == after calling a redis command they expect to compare the result returned from Redis.

Inside a pipelined, we are operating with Redis::Future instances that are BasicObject

BasicObject#== is doing identity comparison instead of value comparison which is less intuitive for developers.

Example:

result = nil

redis.pipelined do 
  result = redis.set('foo', 'bar') == "OK"
end

puts result 
# => false

By removing the ability to use == with a redis future developers would get NoMethodError and this helps to have more consistent errors when operating with Redis::Future inside a pipelined block

[casperisfine]

A couple things:

• I'm generally favorable to this, however redis being very widely used, I think it needs a deprecation period
• There is also the != method
• People can get tricked if they use Yoda comparisons "OK" == redis.set('foo', 'bar'), but I guess that's fine.

[GustavoCaso]

Example of trying to call the == or != method

bin/console
irb(main):001:0> redis = Redis.new
=> #<Redis client v4.1.3 for redis://127.0.0.1:6379/0>
irb(main):002:0> redis.pipelined do
irb(main):003:1* redis.set("foo", "bar") == 'OK"
irb(main):004:1' end
irb(main):005:1' ^C
irb(main):005:0> redis.pipelined do
irb(main):006:1* redis.set("foo", "bar") == 'OK'
irb(main):007:1> end

The method == and != is deprecated for Redis::Future and will be removed in 4.2.0 - You probably meant to call .value == or .value != (in /Users/gustavocaso/src/github.com/redis-rb/lib/redis/pipeline.rb:145:in `==')
=> ["OK"]
irb(main):008:0> redis.pipelined do
irb(main):009:1* redis.set("foo", "bar") != 'OK'
irb(main):010:1> end

The method == and != is deprecated for Redis::Future and will be removed in 4.2.0 - You probably meant to call .value == or .value != (in /Users/gustavocaso/src/github.com/redis-rb/lib/redis/pipeline.rb:145:in `==')
=> ["OK"]
irb(main):011:0>

[GustavoCaso]

I didn't have to deprecate != explicitly since != uses == underneath and we will see two deprecated messages.