Redis script with SMEMBERS call should return empty if key doesn't exist

[FireMasterK]

Describe the bug
When using redis.call('SMEMBERS', '...') on a key that doesn't exist, I get an error, which is different behavior compared to redis.

To Reproduce
Steps to reproduce the behavior:

1. Run a script using redis.call('SMEMBERS', '...') on a key that doesn't exist.

Expected behavior
The script shouldn't throw an error.

Screenshots
If applicable, add screenshots to help explain your problem.

Environment (please complete the following information):

• OS: [ubuntu 24.04]
• Kernel: 6.8.0-50-generic #51-Ubuntu SMP PREEMPT_DYNAMIC Sat Nov 9 17:58:29 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux
• Containerized?: Docker
• Dragonfly Version: Latest build - v1.26.0

Reproducible Code Snippet
I'm using redis-rs to run the script.

local abc = redis.call('SMEMBERS', 'test')

[romange]

what's the error you are getting?

[FireMasterK]

I got an error like this: An error was signalled by the server - ResponseError: Error running script (call to 99f2a53b7a97df8baf906e38cc4f0e26e06a2676): @user_script:8: script tried accessing undeclared key, key: redacted

[romange]

You should pre-declare the keys, see https://www.dragonflydb.io/docs/command-reference/generic/eval#syntax for more details.

[romange]

Please let me know if you have any more questions. There is more material around lua transactions in dragonfly.
See also https://www.dragonflydb.io/docs/managing-dragonfly/scripting . Passing --default_lua_flags=allow-undeclared-keys solves the issue but is unadvised because it hinders perfomance of Dragonfly around lua calls.

[FireMasterK]

Thanks, this is nice, this brings back the compatibility I was looking for with my application!
I have scripts in my application that can fetch additional keys based on arguments and the result of one, so this fixed it!