Using `db: nil` forces the db number to be zero

[sobrinho]

Hi there,

We found an issue with redis-client to a setup like this:

RedisClient.config(url: "redis://localhost:6379/3").db
#=> 3
RedisClient.config(url: "redis://localhost:6379/3", db: 2).db
#=> 2
RedisClient.config(url: "redis://localhost:6379/3", db: nil).db
#=> 0

The problem here is that we use an environment variable that can be set or not and this lead to the wrong db.

The actual code is more like this:

RedisClient.config(url: ENV["REDIS_URL"], db: ENV["REDIS_DB"]&.to_i).db

The Redis gem on the other hand, works as expected:

Redis.new(url: "redis://localhost:6379/3", db: nil)
#=> keeps the 3 db

Redis.new(url: "redis://localhost:6379/3", db: 2)
#=> override to the 2 db

The fix is to not set the db to nil but this was unexpected:

config = { url: ENV["REDIS_URL"] }
config[:db] = ENV["REDIS_DB"].to_i if ENV["REDIS_DB"]
RedisClient.config(config).db
#=> now works as expected if set or unset

We have a few options here:

1. Raise an error if nil
2. Raise an error if db is set to something different than the url db
3. Respect the original dbnumber if set to nil (my choice)

WDYT?

[byroot]

Yes, if initialized with db: nil and the URL does contain an explicit db number, the URL one should be used.