quarkusio/quarkus · error · IllegalArgumentException

Expresion command must not be a digit/alphabetic: " + comman

Error message

Expresion command must not be a digit/alphabetic: " + command

What it means

Thrown by ParserConfig when the expression command character is a digit or alphabetic character. Expression commands must be punctuation so that identifiers/numbers starting templates remain unambiguous.

Source

Thrown at independent-projects/qute/core/src/main/java/io/quarkus/qute/ParserConfig.java:34

     * By default, no special expression command is used.
     */
    public static final ParserConfig DEFAULT = new ParserConfig(null);

    public ParserConfig {
        if (expressionCommand != null) {
            char command = expressionCommand.charValue();
            if (command < 0 || command > 127) {
                throw new IllegalArgumentException("Expresion command must be an ASCII char: " + command);
            }
            if (Parser.Tag.isCommand(command, null)
                    || command == Parser.COMMENT_DELIMITER
                    || command == Parser.CDATA_START_DELIMITER
                    || command == Parser.UNDERSCORE) {
                throw new IllegalArgumentException("Expresion command is reserved: " + command);
            }
            if (Character.isDigit(command)
                    || Character.isAlphabetic(command)) {
                throw new IllegalArgumentException("Expresion command must not be a digit/alphabetic: " + command);
            }
        }
    }

}

View on GitHub (pinned to e1c734241f)

Solutions

1. Use a non-alphanumeric, non-digit ASCII punctuation character such as '$'.
2. Validate before constructing: reject if Character.isDigit(c) || Character.isAlphabetic(c).
3. If a letter-like look is desired, use a symbol adjacent in meaning, e.g. '$' or '%'.

Example fix

// before
ParserConfig config = new ParserConfig('e'); // alphabetic not allowed

// after
ParserConfig config = new ParserConfig('$'); // punctuation is allowed

char c = command;
if (Character.isDigit(c) || Character.isAlphabetic(c)) {
    throw new IllegalArgumentException("expression command must be punctuation, got: " + c);
}

static boolean isPunctuation(char c) {
    return c > 32 && c < 127 && !Character.isDigit(c) && !Character.isAlphabetic(c);
}

try {
    ParserConfig config = new ParserConfig(command);
} catch (IllegalArgumentException e) {
    if (e.getMessage().contains("digit/alphabetic")) {
        // substitute a punctuation char such as '$'
    }
}

When it happens

Trigger: Constructing ParserConfig with e.g. 'x', 'e', or '1' as the expression command — Character.isDigit or Character.isAlphabetic returns true.

Common situations: Users trying a mnemonic delimiter like 'e' for expression or a numeric char; programmatic config generation accidentally passing a letter from a string like "expr".

Related errors

• Expresion command must be an ASCII char: " + command
• Expresion command is reserved: " + command
• Unknown JAR package type '${value}'
• Unable to resolve locale: ${value}
• Unsupported compressor '

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/77f9dae62c4a6e85. Report an issue: GitHub.