configure logging.mask.patterns

Error message

configure logging.mask.patterns[{}] missing 'regex' — skipped

What it means

When parsing a `configure logging.mask` map, each entry in the `patterns` list must contain a `regex` key. If it is missing, LogMask skips that entry and logs this warning instead of failing the whole config eval, so the remaining mask rules still apply.

Solutions

Add the required `regex` key to every entry in the patterns list
Check for key-name typos: the key must be exactly `regex`
If building the config dynamically, filter out entries without a regex before configuring
Check the warned index in the message to locate the offending entry in the list

Example fix

// before
karate.configure('logging.mask', { patterns: [{ replacement: '***' }] })
// after
karate.configure('logging.mask', { patterns: [{ regex: '[0-9]{16}', replacement: '***' }] })

Defensive patterns

Strategy: validation

Validate before calling

var patterns = List.of(Map.of("regex", "[0-9]{16}", "replacement", "***"));
for (var p : patterns) {
    if (!p.containsKey("regex") || p.get("regex") == null)
        throw new IllegalArgumentException("mask pattern entry missing 'regex'");
}

Type guard

boolean hasRegex(Map<?,?> pm) { return pm.get("regex") instanceof String s && !s.isBlank(); }

Prevention

Always include a `regex` key in every patterns entry
Validate mask config keys before calling configure
Build patterns from a shared constant/helper to avoid key typos

When it happens

Trigger: Calling `karate.configure('logging.mask', { patterns: [{ replacement: '***' }] })` — a pattern entry without a `regex` key; also when regex is present but null (e.g. built dynamically from a variable that is null).

Common situations: Typo'd key name (`pattern`, `regEx`, `expression`) instead of `regex`; dynamically assembled mask config where a value failed to load; copy-paste of a headers/jsonPaths-style entry into the patterns list.

Understand the failure class

Background: "is required", "must be set", "missing required field": configuration validation errors across open-source libraries — this error's family across 36 libraries.

Related errors

AI-assisted analysis of karatelabs/karate@a22eb90246 (2026-09-12). Data as JSON: /api/errors/5daa29b626533f31. Report an issue: GitHub.

Appendix: source

Thrown at karate-core/src/main/java/io/karatelabs/output/LogMask.java:114

                }
            }
        }
        List<String> jsonPaths = new ArrayList<>();
        if (map.get("jsonPaths") instanceof List<?> list) {
            for (Object item : list) {
                if (item != null) {
                    jsonPaths.add(item.toString());
                }
            }
        }
        List<PatternRule> patternRules = new ArrayList<>();
        if (map.get("patterns") instanceof List<?> list) {
            int idx = 0;
            for (Object item : list) {
                if (item instanceof Map<?, ?> pm) {
                    Object regex = pm.get("regex");
                    if (regex == null) {
                        logger.warn("configure logging.mask.patterns[{}] missing 'regex' — skipped", idx);
                        idx++;
                        continue;
                    }
                    Object rep = pm.get("replacement");
                    String repStr = rep == null ? replacement : rep.toString();
                    try {
                        patternRules.add(new PatternRule(Pattern.compile(regex.toString()), repStr));
                    } catch (PatternSyntaxException e) {
                        // Skip rather than fail-fast — a typo in one rule shouldn't blow up
                        // the whole config-js eval. The warn names the entry so the user
                        // can find it. Other rules in the same mask still apply.
                        logger.warn("configure logging.mask.patterns[{}] invalid regex '{}': {} — skipped",
                                idx, regex, e.getDescription());
                    }
                }
                idx++;
            }
        }

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