How to update exported variable inside evaluated script?

[elgopher]

I would like to export variable which could be then updated by the evaluated script. I tried the following code but without luck:

package main

import (
	"fmt"
	"reflect"

	"github.com/traefik/yaegi/interp"
)

func main() {
	var variable int // this is a variable which I would like to update inside evaluated script

	interpreter := interp.New(interp.Options{})

	err := interpreter.Use(interp.Exports{
		"main/main": map[string]reflect.Value{
			"variable": reflect.ValueOf(&variable).Elem(),
		},
	})
	if err != nil {
		panic(err)
	}
	if _, err = interpreter.Eval(`import . "main"`); err != nil {
		panic(err)
	}

	var res any
	res, err = interpreter.Eval("variable=3")
	if err != nil {
		panic(err)
	}
	fmt.Println(res)

	fmt.Println(variable) // this should return 3
}

Trying to evaluate variable=3 returns an error:

panic: 1:28: cannot assign to %!s(int=0) (int constant)

Is there any other way to do that?

[elgopher]

I figure it out myself. Here is the working version:

package main

import (
	"fmt"
	"reflect"

	"github.com/traefik/yaegi/interp"
)

func main() {
	var variable int // this is a variable which I would like to update inside evaluated script

	interpreter := interp.New(interp.Options{})

	err := interpreter.Use(interp.Exports{
		"main/main": map[string]reflect.Value{
			"variable": reflect.ValueOf(&variable), // pass the pointer to variable
		},
	})
	if err != nil {
		panic(err)
	}
	if _, err = interpreter.Eval(`import . "main"`); err != nil {
		panic(err)
	}

	var res any
	res, err = interpreter.Eval("*variable=3") // variable name must be prepended with "*"
	if err != nil {
		panic(err)
	}
	fmt.Println(res)

	fmt.Println(variable)
}

[theclapp]

Your solution works, but in my opinion the fact that your first attempt doesn't work is a bug.

#1623