karatelabs/karate · error · RuntimeException

doc() needs at least one argument

Error message

doc() needs at least one argument

What it means

The JS-exposed doc() function accepts variable arguments; when invoked with zero arguments there is no template path to render, so it throws. (It also no-ops with a warning if no onDoc destination is set, but with a destination set, zero args is an error.)

Solutions

1. Pass at least the template path: karate.doc('classpath:doc/template.html')
2. If forwarding from a wrapper, spread the arguments: (...args) => karate.doc(...args)
3. If the intent was only to check rendering setup, remove the call — a no-op destination already logs a warning

Example fix

// before
function renderDoc() { return karate.doc(); }
// after
function renderDoc(path, vars) { return karate.doc(path, vars); }

if (arguments.length === 0) { throw 'doc() needs a template path argument'; }

function canCallDoc(args) { return args && args.length >= 1; }

try { karate.doc.apply(null, args); } catch (RuntimeException e) { if (e.getMessage().contains('needs at least one argument')) { log.error('forward args from wrappers'); } throw e; }

When it happens

Trigger: Calling doc() with no arguments at all from JS, e.g. karate.doc() — usually from generated or scripted code where arguments were meant to be passed through but weren't.

Common situations: A wrapper function forgetting to forward its arguments to doc(); dynamic argument construction that produced an empty array; misuse of doc as a flag rather than a rendering call.

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

• doc() requires 'read' key with template path
• doc() read arg should not be null
• karate.match() needs at least one argument
• karate.call() requires at least one argument (feature path)
• karate.call() with sharedScope requires a feature path

AI-assisted analysis of karatelabs/karate@a22eb90246 (2026-09-12). Data as JSON: /api/errors/810a4081e5744d7e. Report an issue: GitHub.

Appendix: source

Thrown at karate-core/src/main/java/io/karatelabs/core/KarateJs.java:171

        if (read == null) {
            throw new RuntimeException("doc() requires 'read' key with template path");
        }
        String html = markup().processPath(read, null);
        if (onDoc != null) {
            onDoc.accept(html);
        }
        return html;
    }

    @SuppressWarnings("unchecked")
    private JavaInvokable doc() {
        return args -> {
            if (onDoc == null) {
                logger.warn("doc() called, but no destination set");
                return null;
            }
            if (args.length == 0) {
                throw new RuntimeException("doc() needs at least one argument");
            }
            String read;
            if (args[0] instanceof Map) {
                Map<String, Object> map = (Map<String, Object>) args[0];
                read = (String) map.get("read");
            } else if (args[0] == null) {
                read = null;
            } else {
                read = args[0] + "";
            }
            if (read == null) {
                throw new RuntimeException("doc() read arg should not be null");
            }
            Map<String, Object> vars;
            if (args.length > 1) {
                vars = (Map<String, Object>) args[1];
            } else {
                vars = null;

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