Redis [BUG] LPOP key [count] returns Null Bulk reply instead of Null array reply.

Describe the bug

LPOP with count argument returns Null bulk reply instead of array null reply. As per documentation

When called with the count argument:

Array reply: list of popped elements, or nil when key does not exist.

When running against Redis 6.2.6, we get

LPOP NONEXISTINGLIST 10
$-1

instead of

"*-1\r\n"

which is a null array, as documented.

Does the LPOP key [count] always return Bulk Null reply when no list exists to pop from regardless of count is provided or not?

To reproduce

Run the command against Redis 6.2.6

LPOP NONEXISTINGLIST 10

Expected behavior

"*-1\r\n"

Additional Information Issue was first raised in Redis doc.

Comment From: oranagra

looks like you're right. this is a bug in redis 6.2 when COUNT was added

-    robj *o = lookupKeyWriteOrReply(c, c->argv[1], shared.null[c->resp]);
+    robj *o = lookupKeyWriteOrReply(c, c->argv[1], hascount? shared.nullarray[c->resp]: shared.null[c->resp]);

fixing it is a breaking change, but we may wanna do that in 7.0 @itamarhaber please ack.

Comment From: enjoy-binbin

Yes. i also noticed it when we introduced LMPOP, i think we can do that in 7.0

Comment From: itamarhaber

Another mia culpea - acked.

Comment From: oranagra

ok. @enjoy-binbin if you have time, i'd love a PR