`retry.DelayType` gets inconsistent values

[haaawk]

Depending on whether retry.Attempts is set to 0 or something bigger than 0 the function given as retry.DelayType gets n either from 0,1,2,... or 1,2,3,....

Here's a reproducer:

/*
module go-retry-test

go 1.23

require github.com/avast/retry-go/v4 v4.6.0
*/
package main

import (
	"context"
	"errors"
	"time"
)
import "github.com/avast/retry-go/v4"

var count uint64 = 6

func action() error {
	if count == 0 {
		return nil
	}
	count -= 1
	return errors.New("something went wrong")
}

func main() {
	_ = retry.Do(action,
		retry.Attempts(3),
		retry.DelayType(func(n uint, err error, config *retry.Config) time.Duration {
			println("Delay with attempts != 0 -> ", n)
			return time.Second
		}),
		retry.LastErrorOnly(true),
		retry.Context(context.Background()))

	println("")

	_ = retry.Do(action,
		retry.Attempts(0),
		retry.DelayType(func(n uint, err error, config *retry.Config) time.Duration {
			println("Delay with attempts == 0 -> ", n)
			return time.Second
		}),
		retry.LastErrorOnly(true),
		retry.Context(context.Background()))
}

It prints:

Delay with attempts != 0 ->  0
Delay with attempts != 0 ->  1

Delay with attempts == 0 ->  1
Delay with attempts == 0 ->  2
Delay with attempts == 0 ->  3

I would expect the retry.DelayType function to either always get n from 0,1,2,... or always from 1,2,3,... but not one or the other depending on the other config parameters.

[haaawk]

It seems that n=1,2,3,... is the right thing to do based on the documentation -> https://github.com/avast/retry-go/blob/master/options.go#L16