apache/maven · error · IllegalArgumentException

lower function requires exactly one argument

Error message

lower function requires exactly one argument

What it means

lower() is a built-in function of Maven 4.1 profile activation conditions (<activation><condition>). ConditionFunctions.lower throws IllegalArgumentException unless exactly one argument is supplied; the activator reports it as 'Error parsing profile activation condition' and the profile remains inactive.

Source

Thrown at impl/maven-impl/src/main/java/org/apache/maven/impl/model/profile/ConditionFunctions.java:90

     */
    public Object upper(List<Object> args) {
        if (args.size() != 1) {
            throw new IllegalArgumentException("upper function requires exactly one argument");
        }
        String s = ConditionParser.toString(args.get(0));
        return s.toUpperCase();
    }

    /**
     * Converts the given string to lowercase.
     *
     * @param args A list containing a single string argument
     * @return The lowercase version of the input string
     * @throws IllegalArgumentException if the number of arguments is not exactly one
     */
    public Object lower(List<Object> args) {
        if (args.size() != 1) {
            throw new IllegalArgumentException("lower function requires exactly one argument");
        }
        String s = ConditionParser.toString(args.get(0));
        return s.toLowerCase();
    }

    /**
     * Returns a substring of the given string.
     *
     * @param args A list containing 2 or 3 arguments: the string, start index, and optionally end index
     * @return The substring
     * @throws IllegalArgumentException if the number of arguments is not 2 or 3
     */
    public Object substring(List<Object> args) {
        if (args.size() < 2 || args.size() > 3) {
            throw new IllegalArgumentException("substring function requires 2 or 3 arguments");
        }
        String s = ConditionParser.toString(args.get(0));
        int start = toInt(args.get(1));

View on GitHub (pinned to e4093d4e12)

Solutions

1. Rewrite the call as lower(x) with exactly one argument
2. Verify with mvn help:active-profiles that the profile activates
3. Keep a signature table of the condition functions handy when writing activations

Example fix

<!-- before -->
<condition>lower(${os.name}, 'en') == 'linux'</condition>

<!-- after -->
<condition>lower(${os.name}) == 'linux'</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, "lower", 1, 1);

try {
    Object r = new ConditionParser(functions, resolver).parse(condition);
} catch (IllegalArgumentException e) {
    // report and treat the profile as inactive
}

When it happens

Trigger: A condition like lower() or lower(${os.name}, 'en') — the correct form is lower(${os.name}) == 'linux' with one string argument.

Common situations: Copying a locale argument from other APIs; an editing slip leaving an empty argument list; mixing up lower with substring-style multi-argument functions.

Related errors

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

AI-assisted analysis of apache/maven@e4093d4e12 (2026-08-21). Data as JSON: /api/errors/ddb2466b3bde8d03. Report an issue: GitHub.