descent

package main

import (
	"errors"
	"fmt"

	descent "github.com/skalt/descent.go"
)

func main() {
	err := errors.Join(
		errors.New("a"),
		fmt.Errorf("b: %w",
			errors.Join(
				fmt.Errorf("d: %w", errors.New("f")),
				nil,
				errors.New("e"),
			),
		),
		errors.New("c"),
	)
	i := 0
	for e := range descent.BreadthFirst(err) {
		fmt.Printf("%d %T(%#v)\n", i, e, e.Error())
		if e.Error() == "e" {
			break
		}
		i += 1
	}
}

Output:

0 *errors.joinError("a\nb: d: f\ne\nc")
1 *errors.errorString("a")
2 *fmt.wrapError("b: d: f\ne")
3 *errors.errorString("c")
4 *errors.joinError("d: f\ne")
5 *fmt.wrapError("d: f")
6 *errors.errorString("e")

package main

import (
	"errors"
	"fmt"

	descent "github.com/skalt/descent.go"
)

type noChildren string

func (err noChildren) Error() string { return string(err) }
func (noChildren) Unwrap() []error   { return nil }

func main() {
	err := errors.Join(
		errors.New("a"),
		noChildren("b"),
		errors.Join(errors.New("c")),
	)
	for e := range descent.BreadthFirst(err) {
		switch t := e.(type) {
		case interface{ Unwrap() []error }:
			{
				children := t.Unwrap()
				fmt.Printf("%q: %d children\n", e.Error(), len(children))
				for i, child := range children {
					fmt.Printf("  %d. %q\n", i, child.Error())
				}
			}
		case interface{ Unwrap() error }:
			{
				fmt.Printf("%q: 1 child\n", e.Error())
				child := t.Unwrap()
				fmt.Printf("  0. %q\n", child.Error())
			}
		default:
			fmt.Printf("%q (no children)\n", e.Error())
		}
	}
}

Output:

"a\nb\nc": 3 children
  0. "a"
  1. "b"
  2. "c"
"a" (no children)
"b": 0 children
"c": 1 children
  0. "c"
"c" (no children)

package main

import (
	"errors"
	"fmt"

	descent "github.com/skalt/descent.go"
)

func main() {
	err := errors.Join(
		errors.New("a"),
		fmt.Errorf("b: %w",
			errors.Join(
				fmt.Errorf("c: %w", errors.New("d")),
				nil,
				errors.New("e"),
			),
		),
		errors.New("f"),
	)
	i := 0
	for e := range descent.DepthFirst(err) {
		fmt.Printf("%d %T(%#v)\n", i, e, e.Error())
		i += 1
	}
}

Output:

0 *errors.joinError("a\nb: c: d\ne\nf")
1 *errors.errorString("a")
2 *fmt.wrapError("b: c: d\ne")
3 *errors.joinError("c: d\ne")
4 *fmt.wrapError("c: d")
5 *errors.errorString("d")
6 *errors.errorString("e")
7 *errors.errorString("f")