karatelabs/karate · error · RuntimeException

missing argument for headerValues()

Error message

missing argument for headerValues()

What it means

Generic arity guard inside HttpResponse's private headerValues() invokable (reached via getMember): it fires when headerValues() is invoked on a response with zero arguments. The input at fault is the missing header name; with an argument it returns all values for that response header, and without one this sentinel RuntimeException is thrown.

Solutions

1. Pass the header name: `response.headerValues('Set-Cookie')`.
2. Check the name variable is defined/non-null before calling.
3. For a single value use `response.header(name)` instead.
4. ­

Example fix

// before
response.headerValues()
// after
var cookies = response.headerValues('Set-Cookie')

if (name != null) var vals = response.headerValues(name);

function hasHeaderName(v) { return typeof v === 'string' && v.length > 0; }

try { return response.headerValues(name); } catch (e) { if (('' + e).includes('missing argument')) return []; throw e; }

When it happens

Trigger: `response.headerValues()` with zero args, typically when the name variable is undefined or the argument was dropped.

Common situations: Multi-value headers like Set-Cookie where a developer explored the API without the name; refactoring that lost the argument.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• missing argument for header()
• missing argument for header()
• missing argument for headerValues()
• header() needs two arguments
• headers() needs a map argument

AI-assisted analysis of karatelabs/karate@a22eb90246 (2026-09-12). Data as JSON: /api/errors/fb115389f41bb7b9. Report an issue: GitHub.

Appendix: source

Thrown at karate-core/src/main/java/io/karatelabs/http/HttpResponse.java:405

        return args -> {
            if (args.length == 0) {
                throw new RuntimeException("missing argument for header()");
            }
            String name = args[0] + "";
            if (args.length == 1) {
                return getHeader(name);
            }
            putHeaderValue(name, args[1]);
            return null;
        };
    }

    private JavaInvokable headerValues() {
        return args -> {
            if (args.length > 0) {
                return getHeaderValues(args[0] + "");
            } else {
                throw new RuntimeException("missing argument for headerValues()");
            }
        };
    }

    /**
     * Coerce a JS value into the header storage shape ({@code List<String>}).
     * Shared by {@code header(name, value)} and the {@code headers[name] = v}
     * bracket-set path.
     */
    @SuppressWarnings("unchecked")
    void putHeaderValue(String name, Object value) {
        if (value == null) {
            removeHeader(name);
            return;
        }
        if (value instanceof List<?> list) {
            List<String> strList = new ArrayList<>(list.size());
            for (Object o : list) {

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