apache/maven · error · IllegalArgumentException

indexOf function requires exactly two arguments

Error message

indexOf function requires exactly two arguments

What it means

indexOf() is a built-in function of Maven 4.1 profile activation conditions (<activation><condition>). ConditionFunctions.indexOf throws IllegalArgumentException unless exactly two string arguments (haystack, needle) are given; the activator turns it into 'Error parsing profile activation condition' and the profile does not activate.

Source

Thrown at impl/maven-impl/src/main/java/org/apache/maven/impl/model/profile/ConditionFunctions.java:122

        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));
        int end = args.size() == 3 ? toInt(args.get(2)) : s.length();
        return s.substring(start, end);
    }

    /**
     * Finds the index of a substring within a string.
     *
     * @param args A list containing two strings: the main string and the substring to find
     * @return The index of the substring, or -1 if not found
     * @throws IllegalArgumentException if the number of arguments is not exactly two
     */
    public Object indexOf(List<Object> args) {
        if (args.size() != 2) {
            throw new IllegalArgumentException("indexOf function requires exactly two arguments");
        }
        String s = ConditionParser.toString(args.get(0));
        String substring = ConditionParser.toString(args.get(1));
        return s.indexOf(substring);
    }

    /**
     * Checks if a string contains a given substring.
     *
     * @param args A list containing two strings: the main string and the substring to check
     * @return true if the main string contains the substring, false otherwise
     * @throws IllegalArgumentException if the number of arguments is not exactly two
     */
    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));

View on GitHub (pinned to e4093d4e12)

Solutions

1. Use exactly two arguments: indexOf(${os.name}, 'Win') >= 0
2. If you only need a yes/no answer, prefer contains(${os.name}, 'Win')
3. Verify with mvn help:active-profiles after the fix

Example fix

<!-- before -->
<condition>indexOf(${os.name}) >= 0</condition>

<!-- after -->
<condition>indexOf(${os.name}, 'Win') >= 0</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, "indexOf", 2, 2);

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 indexOf(${os.name}) with only the string, or indexOf(${os.name}, 'Win', 0) with a fromIndex — the parser only supports the two-argument form returning the first index or -1.

Common situations: Habit from Java's String.indexOf(str, fromIndex); forgetting the needle; intending contains() but typing indexOf() and dropping an argument.

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
• contains function requires exactly two arguments

AI-assisted analysis of apache/maven@e4093d4e12 (2026-08-21). Data as JSON: /api/errors/1fdcfb8050c4fd2b. Report an issue: GitHub.