tomnomnom/gron · error

invalid integer key `%s`

Error message

invalid integer key `%s`

What it means

During un-groning, a token classified as a numeric array key (typNumericKey) cannot be parsed by strconv.Atoi, so the token text is not a valid integer index. This indicates an internal tokenization inconsistency, since only digit tokens should be tagged typNumericKey.

Source

Thrown at ungron.go:424

	case t.typ == typQuotedKey:
		val, err := ungronTokens(ts[1:])
		if err != nil {
			return nil, err
		}
		key := ""
		err = json.Unmarshal([]byte(t.text), &key)
		if err != nil {
			return nil, fmt.Errorf("invalid quoted key `%s`", t.text)
		}

		out := make(map[string]interface{})
		out[key] = val
		return out, nil

	case t.typ == typNumericKey:
		key, err := strconv.Atoi(t.text)
		if err != nil {
			return nil, fmt.Errorf("invalid integer key `%s`", t.text)
		}

		val, err := ungronTokens(ts[1:])
		if err != nil {
			return nil, err
		}

		// There needs to be at least key + 1 space in the array
		out := make([]interface{}, key+1)
		out[key] = val
		return out, nil

	default:
		return nil, fmt.Errorf("unexpected token `%s`", t.text)
	}
}

// recursiveMerge merges maps and slices, or returns b for scalars

View on GitHub (pinned to 88a6234ea2)

Solutions

1. Inspect the statement that produced the token; the input likely contains a malformed bracket expression with a non-integer index
2. Re-run with the offending input corrected so array keys are plain integers

When it happens

Trigger: Thrown at ungron.go:424 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of tomnomnom/gron@88a6234ea2 (2026-09-06). Data as JSON: /api/errors/ea32e3bbf81c4ecd. Report an issue: GitHub.