quarkusio/quarkus · error · TemplateException

Expression not found for param []:

Error message

Expression not found for param []: 

What it means

After section parameters are parsed, IfSectionHelper looks up each parameter's parsed Expression in a map keyed by the parameter string. If a param string has no corresponding Expression, the condition graph cannot be built and TemplateException is thrown. This is an internal consistency failure: a param survived parsing but never produced an Expression entry.

Source

Thrown at independent-projects/qute/core/src/main/java/io/quarkus/qute/IfSectionHelper.java:738

                block)
                .forEachRemaining(split::add);
        return parseParams(split, block);
    }

    @SuppressWarnings("unchecked")
    static Condition createCondition(Object param, SectionBlock block, Operator operator, SectionInitContext context) {

        Condition condition;

        if (param instanceof String) {
            String stringParam = param.toString();
            boolean logicalComplement = stringParam.startsWith(LOGICAL_COMPLEMENT);
            if (logicalComplement) {
                stringParam = stringParam.substring(1);
            }
            Expression expr = block.expressions.get(stringParam);
            if (expr == null) {
                throw new TemplateException("Expression not found for param [" + stringParam + "]: " + block);
            }
            condition = new OperandCondition(operator, expr);
        } else if (param instanceof List) {
            List<Object> params = (List<Object>) param;
            if (params.size() == 1) {
                return createCondition(params.get(0), block, operator, context);
            }

            List<Condition> conditions = new ArrayList<>();
            Operator nextOperator = null;

            for (Object p : params) {
                if (p instanceof Operator) {
                    nextOperator = (Operator) p;
                } else {
                    conditions.add(createCondition(p, block, nextOperator, context));
                    nextOperator = null;
                }

View on GitHub (pinned to e1c734241f)

Solutions

1. Fix the {#if} expression so every operand is a real expression, no trailing/leading operators or empty operands
2. Upgrade/verify your Quarkus version; if a plain template like {#if a || b} triggers this, file a Quarkus bug with the template
3. If you build condition params programmatically, ensure each param string was registered as an Expression via the normal Parser.parseParams path

Example fix

// before
{#if active && }Done{/if}
// after
{#if active && complete}Done{/if}

try {
    template.render(data);
} catch (TemplateException e) {
    if (e.getMessage().startsWith("Expression not found for param")) {
        log.error("Malformed {#if} operand; check the condition syntax", e);
    }
    throw e;
}

When it happens

Trigger: Calling the package-private createCondition(...) with a String param absent from block.expressions — typically caused by an empty/blank param string (message shows 'param []'), or custom code feeding params into the if-section helpers that bypassed Parser.parseParams/parseSectionParams.

Common situations: Templates with malformed conditions producing an empty operand (e.g. a dangling operator like {#if a && }— parser-level diagnostics usually catch these first); framework regressions or custom section helpers reusing parseParams with hand-built parameter lists.

Related errors

• Not a binary operator:
• Not a short-circuiting operator:
• Invalid composite parameter found:
• Unsupported param type:
• Invalid template link [${templateLink}] - Expeting a link th

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/fb7fa64011b29ef5. Report an issue: GitHub.