apache/maven · error · IllegalArgumentException

matches function requires exactly two arguments

Error message

matches function requires exactly two arguments

What it means

matches() is a built-in function of Maven 4.1 profile activation conditions (<activation><condition>). ConditionFunctions.matches throws IllegalArgumentException unless exactly two string arguments (input, regex) are given; the activator converts it into 'Error parsing profile activation condition' and the profile stays inactive.

Source

Thrown at impl/maven-impl/src/main/java/org/apache/maven/impl/model/profile/ConditionFunctions.java:154

    public Object contains(List<Object> args) {
        if (args.size() != 2) {
            throw new IllegalArgumentException("contains function requires exactly two arguments");
        }
        String s = ConditionParser.toString(args.get(0));
        String substring = ConditionParser.toString(args.get(1));
        return s.contains(substring);
    }

    /**
     * Checks if a string matches a given regular expression.
     *
     * @param args A list containing two strings: the string to check and the regex pattern
     * @return true if the string matches the regex, false otherwise
     * @throws IllegalArgumentException if the number of arguments is not exactly two
     */
    public Object matches(List<Object> args) {
        if (args.size() != 2) {
            throw new IllegalArgumentException("matches function requires exactly two arguments");
        }
        String s = ConditionParser.toString(args.get(0));
        String regex = ConditionParser.toString(args.get(1));
        return s.matches(regex);
    }

    /**
     * Negates a boolean value.
     *
     * @param args A list containing a single boolean argument
     * @return The negation of the input boolean
     * @throws IllegalArgumentException if the number of arguments is not exactly one
     */
    public Object not(List<Object> args) {
        if (args.size() != 1) {
            throw new IllegalArgumentException("not function requires exactly one argument");
        }
        return !ConditionParser.toBoolean(args.get(0));

View on GitHub (pinned to e4093d4e12)

Solutions

1. Always pass two arguments: matches(${java.version}, '17\..*')
2. Test the regex separately (e.g. jshell) before putting it in the condition
3. For simple prefix/suffix checks, prefer contains() or substring(), which cannot fail on pattern syntax

Example fix

<!-- before -->
<condition>matches(${java.version})</condition>

<!-- after -->
<condition>matches(${java.version}, '17\..*')</condition>

static boolean arityOk(String condition, String fn, int min, int max) {
    int i = condition.indexOf(fn + "(");
    if (i < 0) return true;
    String args = condition.substring(i + fn.length() + 1, condition.indexOf(')', i));
    int n = args.isBlank() ? 0 : args.split(",", -1).length;
    return n >= min && n <= max;
}
boolean ok = arityOk(condition, "matches", 2, 2);

try {
    Object r = new ConditionParser(functions, resolver).parse(condition);
} catch (IllegalArgumentException e) {
    // arity problem; a bad regex pattern surfaces as PatternSyntaxException during evaluation
}

When it happens

Trigger: A condition like matches(${java.version}) with only the string — the regex pattern argument is mandatory, e.g. matches(${java.version}, '17\..*').

Common situations: Forgetting the pattern after renaming from another function; assuming the regex can be reused from a variable defined elsewhere in the condition; writing an invalid regex (which then fails separately in String.matches).

Related errors

• length function requires exactly one argument
• upper function requires exactly one argument
• lower function requires exactly one argument
• substring function requires 2 or 3 arguments
• indexOf function requires exactly two arguments

AI-assisted analysis of apache/maven@e4093d4e12 (2026-08-21). Data as JSON: /api/errors/e06191f3bd26c2eb. Report an issue: GitHub.