karatelabs/karate · error · RuntimeException

Unknown operator: " + operator

Error message

Unknown operator: " + operator

What it means

MatchExpression.getMatchTypeName() maps a parsed operator string to its internal enum-style name (e.g. 'contains' -> CONTAINS, 'within' -> WITHIN) via a switch. Any operator value not in the recognized set falls into the default branch and throws a RuntimeException. In practice this indicates the operator string was not produced by the normal parser path or an unsupported operator was constructed manually.

Solutions

1. Use one of the supported operators: ==, !=, contains, !contains, contains only, contains any, contains deep, within, !within (and 'each' variants)
2. Fix the operator string passed when constructing MatchExpression
3. If a new operator is needed, extend both the parser and this switch

Example fix

// before
new MatchExpression(false, "x", "includes", "[1]");
// after
new MatchExpression(false, "x", "contains", "[1]");

static final Set<String> VALID_OPS = Set.of("==","!=","contains","!contains",
    "contains only","contains only deep","contains any","contains any deep",
    "contains deep","within","!within");
// validate before constructing MatchExpression
if (!VALID_OPS.contains(op)) throw new IllegalArgumentException(op);

static boolean isValidOperator(String op) {
    return op != null && (op.equals("==") || op.equals("!=") || op.contains("contains") || op.endsWith("within"));
}

try {
    String type = expr.getMatchTypeName();
} catch (RuntimeException e) {
    if (e.getMessage().startsWith("Unknown operator")) {
        throw new IllegalStateException("Unsupported operator: " + e.getMessage());
    }
    throw e;
}

When it happens

Trigger: Calling getMatchTypeName() (directly or via matchType()) on a MatchExpression whose operator field holds an unrecognized string — e.g. hand-constructing a MatchExpression with a typo like 'includes' or an operator not in the supported set.

Common situations: Programmatic construction of MatchExpression in tests/utilities with invalid operators, or newly added operators not yet covered by the switch.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• Invalid match expression, no operator found: " + expression

AI-assisted analysis of karatelabs/karate@a22eb90246 (2026-09-12). Data as JSON: /api/errors/799665835809fc94. Report an issue: GitHub.

Appendix: source

Thrown at karate-core/src/main/java/io/karatelabs/gherkin/MatchExpression.java:84

    /**
     * Converts operator string to Match.Type enum name.
     * E.g., "==" -> "EQUALS", "contains deep" -> "CONTAINS_DEEP"
     */
    public String getMatchTypeName() {
        String base = switch (operator) {
            case "==" -> "EQUALS";
            case "!=" -> "NOT_EQUALS";
            case "contains" -> "CONTAINS";
            case "!contains" -> "NOT_CONTAINS";
            case "contains deep" -> "CONTAINS_DEEP";
            case "contains only" -> "CONTAINS_ONLY";
            case "contains only deep" -> "CONTAINS_ONLY_DEEP";
            case "contains any" -> "CONTAINS_ANY";
            case "contains any deep" -> "CONTAINS_ANY_DEEP";
            case "within" -> "WITHIN";
            case "!within" -> "NOT_WITHIN";
            default -> throw new RuntimeException("Unknown operator: " + operator);
        };
        return each ? "EACH_" + base : base;
    }

    @Override
    public String toString() {
        return (each ? "each " : "") + actualExpr + " " + operator + " " + expectedExpr;
    }

}

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