apache/maven · error · IllegalArgumentException

length function requires exactly one argument

Error message

length function requires exactly one argument

What it means

length() is a built-in function of Maven 4.1 profile activation conditions (the <activation><condition> element). ConditionFunctions.length validates its argument list and throws IllegalArgumentException unless exactly one argument is given; ConditionProfileActivator catches it and records 'Error parsing profile activation condition: ...', leaving the profile inactive.

Source

Thrown at impl/maven-impl/src/main/java/org/apache/maven/impl/model/profile/ConditionFunctions.java:60

     *
     * @param context The profile activation context
     * @param versionParser The version parser for comparing versions
     */
    public ConditionFunctions(ProfileActivationContext context, VersionParser versionParser) {
        this.context = context;
        this.versionParser = versionParser;
    }

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

    /**
     * Converts the given string to uppercase.
     *
     * @param args A list containing a single string argument
     * @return The uppercase version of the input string
     * @throws IllegalArgumentException if the number of arguments is not exactly one
     */
    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();

View on GitHub (pinned to e4093d4e12)

Solutions

1. Rewrite the call as length(x) with exactly one argument, e.g. length(${project.artifactId}) == 5
2. Re-run mvn help:active-profiles (or the build) to confirm the profile now activates
3. Check the Maven 4.1 condition-function reference for the exact signature before adding more calls

Example fix

<!-- before -->
<condition>length(${project.artifactId}, 0) == 5</condition>

<!-- after -->
<condition>length(${project.artifactId}) == 5</condition>

// Lint a condition expression for the arity of a given function (no nested calls in args)
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, "length", 1, 1);

try {
    Object r = new ConditionParser(functions, resolver).parse(condition);
} catch (IllegalArgumentException e) {
    // wrong arity or bad operand; report the condition string and keep the profile inactive
}

When it happens

Trigger: Writing a condition like length() or length(${name}, 'x') — the function must be called as length(arg) with a single string, e.g. length(${project.artifactId}) == 5.

Common situations: Typing an extra comma or forgetting the argument in a hand-edited condition; copy-pasting expressions from docs of a different function set; upgrading to Maven 4.1 and using the new condition syntax for the first time.

Related errors

• 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
• contains function requires exactly two arguments

AI-assisted analysis of apache/maven@e4093d4e12 (2026-08-21). Data as JSON: /api/errors/37d311081e44ccbf. Report an issue: GitHub.