What causes "Value param not present" in quarkusio/quarkus?

Supply the match value on each branch: `{#is value}...{/is}` or `{#when item.status}{#is 'OK'}...{/when}`.

Value param not present

Error message

Value param not present

What it means

Qute's {#when} section helper requires each branch block (and the main block) to carry a `value` parameter that specifies what the branch matches against. WhenSectionHelper.initializeBlock throws this IllegalStateException when the `value` parameter is absent from a block, i.e. the template's when/case structure is malformed.

Source

Thrown at independent-projects/qute/core/src/main/java/io/quarkus/qute/WhenSectionHelper.java:126

            return ParametersInfo.builder().addParameter(VALUE).build();
        }

        @Override
        public WhenSectionHelper initialize(SectionInitContext context) {
            return new WhenSectionHelper(context);
        }

        @Override
        public List<String> getBlockLabels() {
            return ImmutableList.of(IS, CASE, ELSE);
        }

        @Override
        public Scope initializeBlock(Scope previousScope, BlockInfo block) {
            if (block.getLabel().equals(MAIN_BLOCK_NAME)) {
                String value = block.getParameters().get(VALUE);
                if (value == null) {
                    throw new IllegalStateException("Value param not present");
                }
                Expression valueExpr = block.addExpression(VALUE, value);
                if (valueExpr.hasTypeInfo()) {
                    // If type info is available we do add the expression id
                    previousScope.putAttribute(VALUE_EXPR_ID, valueExpr.getGeneratedId());
                }
            } else if (ELSE.equals(block.getLabel())) {
                // No special handling required for "else"
            } else if (IS.equals(block.getLabel()) || CASE.equals(block.getLabel())) {
                Object valueExprId = previousScope.getAttribute(VALUE_EXPR_ID);
                int added = 0;
                Iterator<String> it = block.getParameters().values().iterator();
                while (it.hasNext()) {
                    String param = it.next();
                    if (added == 0 && it.hasNext()) {
                        // Skip the operator param
                        continue;
                    }

View on GitHub (pinned to e1c734241f)

Solutions

Supply the match value on each branch: `{#is value}...{/is}` or `{#when item.status}{#is 'OK'}...{/when}`.
Verify every `{#is}`/`{#case}` block inside `{#when}` has exactly one value parameter.
Check for typos in the parameter name (it must literally be `value` for the main block form).

Example fix

<!-- before (template) -->
{#when item.status}
  {#is}OK{/is}
{/when}
<!-- after (template) -->
{#when item.status}
  {#is 'OK'}All good{/is}
{/when}

Defensive patterns

Strategy: validation

Validate before calling

// template parse-time check: every {#is}/{#case} block must carry a value
// {#when status}{#is 'OK'}...{/is}{/when}
// This error is thrown during template initialization, so render/parse in tests to catch it early.

Try / catch

try {
    template = Engine.builder().addSectionHelper(new WhenSectionHelperFactory()).build().parse(tpl);
} catch (IllegalStateException e) {
    throw new TemplateInvalidException("malformed {#when} block: " + e.getMessage(), e);
}

Prevention

Always give each {#is}/{#case} branch an explicit value parameter
Parse all templates in CI tests so malformed when-blocks fail the build
Watch for parameter-name typos (value) after refactors

When it happens

Trigger: A `{#when}` or `{#is}`/`{#case}` block is declared without the `value` parameter, so `block.getParameters().get(VALUE)` returns null at WhenSectionHelper.java:126; this occurs at template parsing/build time, not at rendering.

Common situations: Writing `{#is}` with no argument inside a `{#when}` block; template refactoring that dropped the match value; copy-pasting case blocks and removing the parameter; typos in the parameter name.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/eacf5f2c1bc08962. Report an issue: GitHub.