larksuite/cli · error

expected object, got

Error message

expected object, got %v

What it means

OrderedMap.UnmarshalJSON uses a streaming json.Decoder and requires the input to begin with a '{' object token so it can preserve key order. If the first token is anything else (array, string, number, boolean, null), this error is returned.

Solutions

1. Ensure the JSON input is an object starting with '{'
2. Log/inspect the raw payload before unmarshaling to verify its shape
3. Pre-validate the first non-whitespace byte is '{' before calling Decode

Example fix

// before
data := []byte(`[]`)
json.Unmarshal(data, &om) // expected object, got [
// after
data := []byte(`{"a":{}}`)
json.Unmarshal(data, &om)

trimmed := bytes.TrimLeft(raw, " \t\r\n")
if len(trimmed) == 0 || trimmed[0] != '{' {
	return errors.New("payload is not a JSON object")
}
err := json.Unmarshal(raw, &om)

if err := json.Unmarshal(data, &om); err != nil {
	if strings.Contains(err.Error(), "expected object") {
		// payload is not an object: log raw data and recover with defaults
	}
	return err
}

When it happens

Trigger: Calling json.Unmarshal into an OrderedMap (or Property containing one) with JSON input like "[]", "\"str\"", "123", "true", or "null" instead of an object.

Common situations: API response shape changed from object to array or scalar; feeding a JSON fragment into the wrong field; unmarshaling an empty/null payload where an object schema was expected.

Related errors

• expected string key, got
• encoding comma_or_repeated requires an array or slice
• encoding json requires array, object, oneOf, or custom JSON…
• fetch bot info: unmarshal
• invalid v0.2 index

AI-assisted analysis of larksuite/cli@7fd6ef3c07 (2026-09-04). Data as JSON: /api/errors/a9477079b3989cc0. Report an issue: GitHub.

Appendix: source

Thrown at internal/schema/types.go:156

		if err != nil {
			return nil, fmt.Errorf("marshal value for %q: %w", k, err)
		}
		buf.Write(valJSON)
	}
	buf.WriteByte('}')
	return buf.Bytes(), nil
}

// UnmarshalJSON parses an object preserving key order via json.Decoder.Token().
// Used for round-tripping in tests (and future golden update flows).
func (o *OrderedProps) UnmarshalJSON(data []byte) error {
	dec := json.NewDecoder(bytes.NewReader(data))
	tok, err := dec.Token()
	if err != nil {
		return err
	}
	if delim, ok := tok.(json.Delim); !ok || delim != '{' {
		return fmt.Errorf("expected object, got %v", tok)
	}
	o.Order = nil
	o.Map = make(map[string]Property)
	for dec.More() {
		keyTok, err := dec.Token()
		if err != nil {
			return err
		}
		key, ok := keyTok.(string)
		if !ok {
			return fmt.Errorf("expected string key, got %v", keyTok)
		}
		var prop Property
		if err := dec.Decode(&prop); err != nil {
			return err
		}
		o.Order = append(o.Order, key)
		o.Map[key] = prop

View on GitHub (pinned to 7fd6ef3c07)