Redis [BUG] APPEND KEY "" creates an empty string

Describe the bug

Appending "" to an empty key creates an empty string. To my knowledge, a string with an empty value is equivalent to a nil value in redis so the value should not be created.

To reproduce

Append an empty string to a missing key.

127.0.0.1:6379> type x
none
127.0.0.1:6379> append x ""
(integer) 0
127.0.0.1:6379> type x
string

Expected behavior

No key should be created.

127.0.0.1:6379> type x
none
127.0.0.1:6379> append x ""
(integer) 0
127.0.0.1:6379> type x
none

Additional information

Using redis 6.2.5.

Comment From: mgravell

Conversely, though:

127.0.0.1:6379> type x
none
127.0.0.1:6379> exists x
(integer) 0
127.0.0.1:6379> get x
(nil)

127.0.0.1:6379> set x ""
OK

127.0.0.1:6379> type x
string
127.0.0.1:6379> exists x
(integer) 1
127.0.0.1:6379> get x
""

An empty string can exist and have a type.

Comment From: sundb

@braddunbar An empty string is not the same as null, which is allowed in redis.

Comment From: braddunbar

Huh…I was really wrong about that. Thanks @sundb and @mgravell! I'll close this and continue on then. 😆