AskOne with default set to empty string and required may still be empty

[vgarvardt]

What operating system and terminal are you using? OS: MacOS 10.15.7 Terminal: zsh 5.8 (x86_64-apple-darwin19.6.0)

An example that showcases the bug.

I use survey lib to populate a struct - it can be either pre-filled with some values already or be empty. Recently updated from v1 to v2 and found an interesting issue. In v1 Default field used to be string, but in v2 it is interface{} and it causes an issue with defining defaults.

When default value is set to an empty string select interface shows correct graphics (the first item is selected by default):

but pressing return (enter) writes an empty string to the response. If I move select down and up then it is set to the correct value. If Default is not set at all - it works as expected - the first element that is displayed as selected is being written to the response.

package main

import (
	"fmt"

	survey2 "github.com/AlecAivazis/survey/v2"
	"gopkg.in/AlecAivazis/survey.v1"
)

type mySetup struct {
	question1 string
	question2 string
	question3 string
}

func main() {
	var initialSetup mySetup

	promptOneV1 := &survey.Select{
		Message: "Choose one using survey.v1",
		Options: []string{"foo1", "bar1", "baz1"},
		Default: initialSetup.question1,
	}

	if err := survey.AskOne(promptOneV1, &initialSetup.question1, survey.Required); err != nil {
		panic(err)
	}

	promptOneV2 := &survey2.Select{
		Message: "Choose one using survey/v2",
		Options: []string{"foo2", "bar2", "baz2"},
		Default: initialSetup.question2,
	}

	if err := survey2.AskOne(promptOneV2, &initialSetup.question2, survey2.WithValidator(survey2.Required)); err != nil {
		panic(err)
	}

	promptOneV2NoDefault := &survey2.Select{
		Message: "Choose one using survey/v2 w/out default",
		Options: []string{"foo3", "bar3", "baz3"},
	}

	if err := survey2.AskOne(promptOneV2NoDefault, &initialSetup.question3, survey2.WithValidator(survey2.Required)); err != nil {
		panic(err)
	}

	fmt.Printf("Your choices: %s; %s; %s\n", initialSetup.question1, initialSetup.question2, initialSetup.question3)
}

What did you expect to see?

❯ go run ./main.go
? Choose one using survey.v1 foo1
? Choose one using survey/v2 foo2
? Choose one using survey/v2 w/out default foo3
Your choices: foo1; foo2; foo3

What did you see instead?