karatelabs/karate · error

Invalid number: missing fraction digits

Error message

Invalid number: missing fraction digits

What it means

JSON syntax error raised by parseNumber in JsonParser (via parseValue): after consuming the '.' that starts a fractional part, the parser requires at least one digit; the input at fault is the number literal in the JSON text whose fraction is empty or truncated (e.g. "1." or "1." followed by a non-digit), so the literal cannot form a valid number.

Solutions

1. Append the missing fraction digits: '1.' -> '1.0'.
2. Fix the formatter that produced the literal so it never emits a trailing '.' without digits.
3. Check for payload truncation (size limits, log rotation) cutting the token mid-way.
4. Round the value to an integer instead if no fractional part is meaningful.

Example fix

// before
String lit = String.valueOf(value).replaceAll("\\.0+$", "."); // 5.0 -> 5.
// after
String lit = String.valueOf(value).replaceAll("\\.0+$", ""); // 5.0 -> 5

// detect numbers ending in a bare decimal point before parsing
if (json.matches(".*\\d\\.([^0-9]|$).*")) {
    throw new IllegalArgumentException("JSON number has a decimal point with no fraction digits");
}

// Java
try {
    Json json = Json.of(raw);
} catch (Exception e) {
    if (String.valueOf(e.getMessage()).contains("missing fraction digits")) {
        raw = raw.replaceAll("(\\d)\\.(?=[^0-9]|$)", "$1.0");
    } else { throw e; }
}

When it happens

Trigger: Parsing JSON containing numbers truncated right after the decimal point: '[1., 2]', '{"price": 9.9.}' misses digits, or '1.' at end of input — commonly produced by toFixed-style formatting that strips trailing zeros, or truncated network payloads.

Common situations: Formatting code that emits 'x.' after removing trailing zeros; log/config files truncated mid-token; template expressions like '{{price}}.' where price lost its decimals.

Understand the failure class

Background: JSON parse error: "Unexpected token" / "not valid JSON" / "failed to parse" — what JSON parsers are really complaining about — this error's family across 45 libraries.

Related errors

• Invalid number: bare '-'
• Invalid number
• Invalid number: missing exponent digits
• Unexpected token ' ' in JSON
• Expected string key in object

AI-assisted analysis of karatelabs/karate@a22eb90246 (2026-09-12). Data as JSON: /api/errors/ab60c30f5a4d307f. Report an issue: GitHub.

Appendix: source

Thrown at karate-js/src/main/java/io/karatelabs/js/JsonParser.java:285

                pos++;
            } else if (c >= '1' && c <= '9') {
                pos++;
                while (pos < len && (s.charAt(pos) >= '0' && s.charAt(pos) <= '9')) {
                    pos++;
                }
            } else {
                throw syntaxError("Invalid number");
            }
            // fraction
            if (pos < len && s.charAt(pos) == '.') {
                isFloat = true;
                pos++;
                int fracStart = pos;
                while (pos < len && (s.charAt(pos) >= '0' && s.charAt(pos) <= '9')) {
                    pos++;
                }
                if (pos == fracStart) {
                    throw syntaxError("Invalid number: missing fraction digits");
                }
            }
            // exponent
            if (pos < len && (s.charAt(pos) == 'e' || s.charAt(pos) == 'E')) {
                isFloat = true;
                pos++;
                if (pos < len && (s.charAt(pos) == '+' || s.charAt(pos) == '-')) {
                    pos++;
                }
                int expStart = pos;
                while (pos < len && (s.charAt(pos) >= '0' && s.charAt(pos) <= '9')) {
                    pos++;
                }
                if (pos == expStart) {
                    throw syntaxError("Invalid number: missing exponent digits");
                }
            }
            String lit = s.substring(start, pos);

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