Unexpected results with padded strings

[James Sumners]

https://play.golang.com/p/3oTZVLEkdas

package main

import (
	"fmt"
	"github.com/spf13/cast"
)

func main() {
	x := cast.ToInt("08")
	fmt.Printf("08 => %d\n", x)
	
	x = cast.ToInt("8")
	fmt.Printf("8 => %d\n", x)
}

I'd expect the result to be 8 in each scenario. However, "08" ends up hitting a path where the base is changed and the parsing returns an error that we don't see.

[Jundan Zhang]

By reading the source code, I found that this problem occurs because 0 is the prefix of octal (just like 0x for hex). Maybe you can discard the leading 0 first.

[James Sumners]

Yes, that is what I stated in the original report. The path is

1. cast/caste.go

   Lines 491 to 496 in ba0a5b6

    case string: 
    	v, err := strconv.ParseInt(trimZeroDecimal(s), 0, 0) 
    	if err == nil { 
    		return int(v), nil 
    	} 
    	return 0, fmt.Errorf("unable to cast %#v of type %T to int64", i, i) 

2. https://cs.opensource.google/go/go/+/refs/tags/go1.20.3:src/strconv/atoi.go;l=202
3. https://cs.opensource.google/go/go/+/refs/tags/go1.20.3:src/strconv/atoi.go;l=78
4. https://cs.opensource.google/go/go/+/refs/tags/go1.20.3:src/strconv/atoi.go;l=107
5. https://cs.opensource.google/go/go/+/refs/tags/go1.20.3:src/strconv/atoi.go;l=131
6. https://cs.opensource.google/go/go/+/refs/tags/go1.20.3:src/strconv/atoi.go;l=145
7. https://cs.opensource.google/go/go/+/refs/tags/go1.20.3:src/strconv/atoi.go;l=153
8. https://cs.opensource.google/go/go/+/refs/tags/go1.20.3:src/strconv/atoi.go;l=53
9. https://cs.opensource.google/go/go/+/refs/tags/go1.20.3:src/strconv/atoi.go;l=225

10. cast/caste.go

    Line 496 in ba0a5b6

     return 0, fmt.Errorf("unable to cast %#v of type %T to int64", i, i) 

The point is, cast.ToInt should consider leading 0 characters and do the right thing. Basically, I would only support 0o (0O) to indicate octals when casting (https://go.dev/ref/spec#Integer_literals).

[Jundan Zhang]

https://play.golang.com/p/mPCpDwylr7T

Thank you for the explanation. In my opinion, if cast.ToInt considers leading 0 characters, cast.ToInt("012") will return 12, but int variables with value 012 is 10 in Go(like above). I think this might not be appropriate.