Redis branch: latest unstable at commit c552fad

Issue statement

It appears that redis module API RedisModule_HashSet() was returning 0 for the creation of a new hash type key which did not previously exist. It however returns the number of fields updated for a hash type key which previsouly existed.
Since a return value of 0 is currently considered an error by RedisModule_HashSet(), it becomes confusing to determine whether the HashSet is successful or not based on the return value.

Expected behavior

The return value for a successful new hash key creation by RedisModule_HashSet() shoud differ from the error return code.

To reproduce the issue

                int ret;
                RedisModuleKey *hash_key_ptr = RedisModule_OpenKey(ctx, hash_key,
                    REDISMODULE_READ|REDISMODULE_WRITE);
                keytype = RedisModule_KeyType(hash_key_ptr);
                
                if (keytype != REDISMODULE_KEYTYPE_HASH &&
                    keytype != REDISMODULE_KEYTYPE_EMPTY)
                {
                    RedisModule_CloseKey(hash_key_ptr);
                    return RedisModule_ReplyWithError(ctx,REDISMODULE_ERRORMSG_WRONGTYPE);
                }

                ret = RedisModule_HashSet(hash_key_ptr, REDISMODULE_HASH_CFIELDS,
                                          "field1", value1,
                                          "field2", value2,
                                          "field3", value3,
                                          NULL);

Return value ret was found to be 0.
The hash key was found to be written successfully.

Root cause analysis

module.c

int RM_HashSet(RedisModuleKey *key, int flags, ...) {
...
2783 int updated = 0;
...
2823 robj *argv[2] = {field,value};
2824 hashTypeTryConversion(key->value,argv,0,1);
2825 updated += hashTypeSet(key->value, field->ptr, value->ptr, low_flags);
...
2836 return updated;

hashTypeSet() returns the number of updated fields ONLY (i.e. the field must previsously exist).
If the field is new (in the case of creating a new hash key), hashTypeSet returns 0 even though the field is created.
Hence for RM_HashSet(), variable "updated" was not incremented for any field when creating a new hash key and 0 is returned to caller, although the hash key creation was successful.