What causes "cannot parse object value: %s" in vitessio/vitess?

Fix the invalid value at the reported position in the object

cannot parse object value: %s

Error message

cannot parse object value: %s

What it means

While parsing a JSON object, the value after a valid key:colon failed in parseValue; the error is wrapped as 'cannot parse object value:'. The inner error identifies why the value (number, string, literal, etc.) was rejected.

Source

Thrown at go/mysql/json/parser.go:555

		}
		kv.k, s, unescape, err = parseRawKey(s[1:])
		if err != nil {
			return nil, s, fmt.Errorf("cannot parse object key: %s", err)
		}
		if unescape {
			kv.k = unescapeStringBestEffort(kv.k)
		}
		s = skipWS(s)
		if len(s) == 0 || s[0] != ':' {
			return nil, s, errors.New("missing ':' after object key")
		}
		s = s[1:]

		// Parse value
		s = skipWS(s)
		kv.v, s, err = parseValue(s, c, depth)
		if err != nil {
			return nil, s, fmt.Errorf("cannot parse object value: %s", err)
		}
		s = skipWS(s)
		if len(s) == 0 {
			return nil, s, errors.New("unexpected end of object")
		}
		if s[0] == ',' {
			s = s[1:]
			continue
		}
		if s[0] == '}' {
			o.o.sort()
			return o, s[1:], nil
		}
		return nil, s, errors.New("missing ',' after object value")
	}
}

const hexDigits = "0123456789abcdef"

View on GitHub (pinned to 01a25a7d17)

Solutions

Fix the invalid value at the reported position in the object
Ensure values are always serialized (never emit empty strings for numbers/objects)
Validate the JSON document with a standard parser before handing it to mysql.ParseJSON

Example fix

// before
v, err := mysql.ParseJSON(`{"k": }`)
// after
v, err := mysql.ParseJSON(`{"k": null}`)

Defensive patterns

Strategy: try-catch

Validate before calling

if !json.Valid([]byte(input)) {
	return fmt.Errorf("invalid JSON document: %q", input)
}

Try / catch

v, err := mysql.ParseJSON(input)
if err != nil {
	if strings.Contains(err.Error(), "cannot parse object value") {
		// the value after a key:colon is malformed; reject or repair
	}
	return err
}

Prevention

Never interpolate possibly-empty variables into JSON templates — marshal a struct instead
Use encoding/json to build objects so values are always well-formed
Validate documents with json.Valid at ingest boundaries

When it happens

Trigger: Parsing `{"k": }` (empty value), `{"k": q}` (bare word), or an object value that is an oversized number or malformed literal.

Common situations: Template-generated JSON where a variable rendered empty; corrupted column/binlog data; hand-edited JSON documents.

Related errors

AI-assisted analysis of vitessio/vitess@01a25a7d17 (2026-09-01). Data as JSON: /api/errors/00f4cd9b6166b48b. Report an issue: GitHub.