kubernetes/kops · error

unknown delim: %v

Error message

unknown delim: %v

What it means

JSONStreamWriter.WriteToken received a json.Delim token that is not one of { [ ] }. The writer maintains pretty-printing state per delimiter, so any other delim byte cannot be serialized. This normally indicates corrupted or manually fabricated tokens being fed to the writer rather than tokens from a real json.Decoder.

Source

Thrown at pkg/jsonutils/streamwriter.go:89

			j.indent += "  "
			j.state += "{"
		case json.Delim('['):
			j.indent += "  "
			j.state += "["
		case json.Delim(']'), json.Delim('}'):
			j.indent = j.indent[:len(j.indent)-2]
			indent = j.indent
			j.state = j.state[:len(j.state)-1]
			if j.state != "" && j.state[len(j.state)-1] == 'F' {
				j.state = j.state[:len(j.state)-1]
				j.path = j.path[:len(j.path)-1]
			}
			// Don't put a comma on the last field in a block
			if j.deferred == ",\n" {
				j.deferred = "\n"
			}
		default:
			return fmt.Errorf("unknown delim: %v", tt)
		}

		switch state {
		case 0:
			if err := j.writeRaw(indent + v); err != nil {
				return err
			}
		case '{':
			if err := j.writeRaw(indent + v); err != nil {
				return err
			}
		case '[':
			if err := j.writeRaw(indent + v); err != nil {
				return err
			}
		case 'F':
			if err := j.writeRaw(v); err != nil {
				return err

View on GitHub (pinned to 4c8573c808)

Solutions

1. Only pass tokens obtained from a json.Decoder iterating valid JSON text into WriteToken.
2. Check that the delimiter is one of { [ ] } before calling WriteToken, or skip punctuation tokens.
3. If you need to write raw syntax characters, use writeRaw-style output or a plain writer, not WriteToken.

Example fix

// before
w.WriteToken(json.Delim(':'))
// after
if d, ok := tok.(json.Delim); ok && (d == '{' || d == '[' || d == ']' || d == '}') {
	w.WriteToken(tok)
} else {
	// skip non-structural delimiter tokens
}

func isStructuralDelim(t json.Token) bool {
	d, ok := t.(json.Delim)
	return ok && (d == '{' || d == '[' || d == ']' || d == '}')
}
// call: if isStructuralDelim(tok) { w.WriteToken(tok) }

func isStructuralDelim(t json.Token) bool {
	d, ok := t.(json.Delim)
	return ok && (d == '{' || d == '[' || d == ']' || d == '}')
}

When it happens

Trigger: Calling WriteToken with a json.Delim value constructed manually (e.g. json.Delim(':') or json.Delim(',')), or re-tokenizing text that was not valid JSON so the decoder yields unexpected delim bytes.

Common situations: Custom JSON rewriting tools that synthesize tokens instead of iterating a json.Decoder over valid JSON; feeding fragments of JSON (e.g. a key/value pair including its colon) through the stream writer.

Related errors

• unhandled state for json delim serialization: %v %q
• unhandled token type %T
• unhandled state for json value (%T %q) serialization: %v %q
• error parsing version spec %q
• error encoding version spec: %v

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/b1473ec8eb16e85b. Report an issue: GitHub.