YAML 1.2: Error parsing C1 control character inside double-quoted string

[0f-0b]

package main

import (
	"fmt"

	"go.yaml.in/yaml/v4"
)

func main() {
	var str string
	err := yaml.Unmarshal([]byte("\"\u0080\""), &str)
	if err != nil {
		fmt.Println(err)
	}
}

This program should exit without printing anything, but it reports the error yaml: control characters are not allowed. To quote the YAML 1.2 specification, “YAML processors must allow all non-C0 characters inside quoted scalars.”

[ingydotnet]

This works for me:

$ make go-yaml 
go build -o go-yaml ./cmd/go-yaml
$ ./go-yaml -u -n <<<'"\u0080"'
kind: Document
content:
  - kind: Scalar
    style: Double
    text: "\x80"

Did you mean?:

err := yaml.Unmarshal([]byte("\"\\u0080\""), &str)

Your program with that change runs without error.

[0f-0b]

No. I specifically meant "\"\u0080\"" with the unescaped C1 control, which should be allowed under YAML 1.2. It's only C0 controls that may be disallowed.

[ingydotnet]

Can reproduce with:

$ ./go-yaml -t <<<$'"\u0080"'
2025/11/26 09:56:12 Failed to process tokens:failed to get next token: parser error: control characters are not allowed

go-yaml is not yet declared to be at 1.2, but this should be fixed to further the cause.

[colinjlacy]

I'll take this one