Problem about overflow inspection of INCRBY/DECRBY

[z4deepfz]

Miniredis throws out no error of overflowing when the value becomes greater than math.MaxInt64 after INCRBY or DECRBY (also INCR or DECR). Instead it returns a negative number which was exactly the overflowed value. As a comparison, the real redis instance returns ERR increment or decrement would overflow which thrown out by overflow detection and nothing will be changed.

I found the cause of it and some potential issues as well. I can make a patch to it if it is indeed an unexpected behavior of miniredis.

The following code reproduces the problem.

package main

import(
    "log"
    "math"
    "github.com/alicebob/miniredis/v2"
    "github.com/gomodule/resign/redis"
)

func main() {
    server, _ := miniredis.Run()
    minirds, _ := redis.Dial("tcp", server.Addr())
    defer miniredis.Close()
    realrds, _ := redis.Dial("tcp", "127.0.0.1:6379") // redis instance
    defer realrds.Close()
    overflowTest(minirds)
    overflowTest(realrds)
}

func overflowTest(r redis.Conn) {
    _, _ = r.Do("SET", "number", 100)
    rsp, err := redis.Int64(r.Do("INCRBY", "number", math.MaxInt64)
    if err != nil {
        log.Printf("got an error when exec INCRBY, err=%v", err)
    }
    log.Printf("got=%d", rsp)
}

[alicebob]

Thanks for opening this issue.

I found the cause of it and some potential issues as well. I would like to make a patch to miniredis if it is indeed an unexpected behavior of miniredis.

Sounds like a good improvement to me, a PR would be appreciated.