@enjoy-binbin can you scan other places where COUNT was added in 6.2 and other early exists of these commands to see if we don't have similar issues in other places.

sure, i can take a look tomorrow

@madolson it does match 6.0 already.
6.0 didn't have the count argument, so it always returned null string in this case

@oranagra For some reason I thought this broke from 6.0->6.2, but I understand now, it doesn't change my opinion.

base on this branch (this PR)

saying up front, i scanned most of the commands, here is the result:
it looks like we've got everything covered

shared.emptyarray = createObject(OBJ_STRING,sdsnew("*0\r\n"));

shared.null[2] = createObject(OBJ_STRING,sdsnew("$-1\r\n"));
shared.null[3] = createObject(OBJ_STRING,sdsnew("_\r\n"));

shared.nullarray[2] = createObject(OBJ_STRING,sdsnew("*-1\r\n"));
shared.nullarray[3] = createObject(OBJ_STRING,sdsnew("_\r\n"));

shared.emptymap[2] = createObject(OBJ_STRING,sdsnew("*0\r\n"));
shared.emptymap[3] = createObject(OBJ_STRING,sdsnew("%0\r\n"));

shared.emptyset[2] = createObject(OBJ_STRING,sdsnew("*0\r\n"));
shared.emptyset[3] = createObject(OBJ_STRING,sdsnew("~0\r\n"));

list:

LPOP/RPOP key [count] (count added in 6.2)

• without count:
  • non existing: return shared.null[resp]
• with count:
  • non existing: now we return shared.nullarray[resp] (this PR fix it)
  • count is 0: return shared.emptyarray (used to return addReplyNullArray, fixed it in Fixes LPOP/RPOP wrong replies when count is 0 #9692)

set:

SPOP key [count] (count added in 3.2)

• without count:
  • non existing: return shared.null[c->resp]
• with count:
  • non existing: return shared.emptyset[c->resp] (used to return shared.null[resp], we fixed it in SPOP returns an empty bulk instead of nil #4709)
  • count is 0: return shared.emptyset[resp] (used to return addReplyNull, ie: shared.null[resp], fixed it in 06d4903)

SRANDMEMBER

• without count:
  • non existing: return shared.null[c->resp]
• with count:
  • non existing key / count is 0: return shared.emptyarray (used to return emptyset[c->resp], fixed it in SRANDMEMBER RESP3 return should be Array, not Set #8504)

zset:

ZPOPMIN/ZPOPMAX key [count]

• without count:
  • non existing zset: return shared.emptyarray
• with count:
  • non existing: return shared.emptyarray
  • count is 0: return shared.emptyarray

ZRANDMEMBER

• without count:
  • non existing: return shared.null[c->resp]
• with count:
  • non existing: return shared.emptyarray (used to return null[c->resp], fixed it in hrandfield and zrandmember with count should return emptyarray when key does not exist. #9178)
  • count is 0: return shared.emptyarray

hash:

HGETALL key
non existing: return shared.emptymap[c->resp] (used to return shared.emptyarray, fixed it in #7781)

HRANDFIELD

• without count:
  • non existing: return shared.null[c->resp]
• with count:
  • non existing: return shared.emptyarray (used to return null[c->resp], fixed it in hrandfield and zrandmember with count should return emptyarray when key does not exist. #9178)
  • count is 0: return shared.emptyarray

geo:

georadius*
geosearch

• non existing key: return addReply(c, shared.emptyarray);
• non existing key with store key: return 0 (used to return emptyarray, fixed it in GEO* STORE with empty src key delete the dest key and return 0, not empty array #9271)