How to fix ERR bad lua script for redis cluster, all the keys that the script uses should be passed using the KEYS array in Redis

-- ❌ WRONG: Using Lua variable for key name
local key = "user:123"
redis.call('GET', key)

-- ❌ WRONG: String concatenation
redis.call('SET', 'user:' .. userId, value)

-- ❌ WRONG: Keys in expressions
local keys = {'key1', 'key2'}
redis.call('GET', keys[1])

-- ✅ CORRECT: Using KEYS array
redis.call('GET', KEYS[1])
redis.call('SET', KEYS[2], ARGV[1])

-- ✅ CORRECT: Multiple keys from KEYS array
for i = 1, #KEYS do
  redis.call('DEL', KEYS[i])
end

# ❌ WRONG: No keys declared
EVAL "return redis.call('GET', 'user:123')" 0

# ✅ CORRECT: Declare 1 key
EVAL "return redis.call('GET', KEYS[1])" 1 user:123

# ✅ CORRECT: Multiple keys and arguments
EVAL "return redis.call('SET', KEYS[1], ARGV[1])" 1 user:123 "John"

// Node.js ioredis
await redis.eval(
  "return redis.call('GET', KEYS[1])",
  1,              // number of keys
  'user:123'      // key name
);

// Python redis-py
redis.eval(
  "return redis.call('SET', KEYS[1], ARGV[1])",
  1,              # numkeys
  'user:123',     # key
  'value'         # argument
)

-- ✅ CORRECT: Hash tags ensure same slot
redis.call('GET', KEYS[1])  -- {user:123}:profile
redis.call('GET', KEYS[2])  -- {user:123}:settings

await redis.eval(
  script,
  2,
  '{user:123}:profile',    // Same hash tag {user:123}
  '{user:123}:settings'    // Same hash tag {user:123}
);

# Test with Redis CLI
redis-cli --cluster call <host>:6379 EVAL "return redis.call('GET', KEYS[1])" 1 testkey

# Check cluster slot assignment
redis-cli CLUSTER KEYSLOT testkey

try {
  const result = await redis.eval(script, numKeys, ...keys, ...args);
  console.log('Script executed successfully:', result);
} catch (error) {
  if (error.message.includes('bad lua script')) {
    console.error('Script still uses dynamic keys - review KEYS array usage');
  } else if (error.message.includes('CROSSSLOT')) {
    console.error('Keys are in different slots - use hash tags');
  }
  throw error;
}