Error when using `BytesUnmarshaler` together with array aliases

[Joshua Sangmeister]

Describe the bug

When an anchor is defined for an array and it is aliased in a node which has a custom unmarshaler, the unmarshaling fails if the indentation of the anchor and the alias do not match.

To Reproduce

main.go:

package main

import (
	"fmt"
	"os"

	"github.com/goccy/go-yaml"
)

type Document struct {
	Data struct {
		Element struct {
			List []string
			Other bool
		}
	}
}

func (d *Document) UnmarshalYAML(node []byte) error {
	return yaml.Unmarshal(node, &d)
}

func main() {
	r, _ := os.Open("test.yml")
	var d Document
	err := yaml.NewDecoder(r).Decode(&d)
	fmt.Println(err)
}

test.yml:

list: &list
  - a
  - b
  - c

data:
  element:
    list: *list
    other: true

When running go run main.go, the following error is printed:

[10:5] unexpected key name
       7 | null
       8 |   - a
       9 |   - b
    > 10 |   - c
      11 |     other: true
               ^

Expected behavior
The alias should be parsed without error.

Version Variables

• Go version: 1.22
• go-yaml's Version: v1.11.3

Additional context
The test.yml file is valid YAML according to, e.g., https://www.yamllint.com/. We strongly suspect that the error stems from a simple string replacement, where aliases are simply replaced with the string content of the anchor before unmarshaling.