karatelabs/karate · error · RuntimeException

filterKeys() needs at least two arguments

Error message

filterKeys() needs at least two arguments

What it means

Karate's filterKeys() JS utility builds a new map containing only selected keys of a source map (by a keys map, array, or varargs). It requires at least two arguments: the source map plus a key selector; fewer throw this error.

Solutions

1. Pass the keys to keep: filterKeys(map, ['a','b']) or filterKeys(map, {a:1})
2. Verify the variable holding the key list is defined and non-empty
3. Remember the source must be a Map — convert XML via Xml/Json first if needed

Example fix

// before
var trimmed = karate.filterKeys(response);
// after
var trimmed = karate.filterKeys(response, ['id', 'name']);

if (!map || !keys || (Array.isArray(keys) && keys.length === 0)) throw new Error('filterKeys requires a map and key selector');

function canFilterKeys(args) { return args.length >= 2 && args[0] != null && args[1] != null; }

try { trimmed = karate.filterKeys(map, keys); } catch (e) { karate.log('filterKeys failed: ' + e.message); }

When it happens

Trigger: Calling filterKeys(map) with only the map, or filterKeys() with no arguments; passing null as the second argument.

Common situations: Stripping a response field but forgetting the key list; dynamic key lists that end up undefined; confusing with filter() which expects a function.

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

• eval() needs one argument
• expect() needs at least one argument
• append() needs at least two arguments
• appendTo() needs at least two arguments: list and item(s)
• extract() needs three arguments: text, regex, group

AI-assisted analysis of karatelabs/karate@a22eb90246 (2026-09-12). Data as JSON: /api/errors/730ce9abc807fe90. Report an issue: GitHub.

Appendix: source

Thrown at karate-core/src/main/java/io/karatelabs/core/KarateJsUtils.java:203

            List<?> list = (List<?>) args[0];
            JavaCallable fn = (JavaCallable) args[1];
            List<Object> result = new ArrayList<>();
            for (int i = 0; i < list.size(); i++) {
                Object item = list.get(i);
                Object keep = fn.call(null, new Object[]{item, i});
                if (Boolean.TRUE.equals(keep)) {
                    result.add(item);
                }
            }
            return result;
        };
    }

    @SuppressWarnings("unchecked")
    static JavaInvokable filterKeys() {
        return args -> {
            if (args.length < 2) {
                throw new RuntimeException("filterKeys() needs at least two arguments");
            }
            Map<String, Object> source = (Map<String, Object>) args[0];
            Map<String, Object> result = new LinkedHashMap<>();

            if (args[1] instanceof Map) {
                // filterKeys(source, keysFromMap) - filter by keys present in the map
                Map<String, Object> keysMap = (Map<String, Object>) args[1];
                for (String key : keysMap.keySet()) {
                    if (source.containsKey(key)) {
                        result.put(key, source.get(key));
                    }
                }
            } else if (args[1] instanceof List) {
                // filterKeys(source, [key1, key2, ...])
                List<String> keys = (List<String>) args[1];
                for (String key : keys) {
                    if (source.containsKey(key)) {
                        result.put(key, source.get(key));

View on GitHub (pinned to a22eb90246)