Qute: Rendering Timeout Instead of Throwing TemplateException for Missing Keys in {#let} and {#set} Constructs

[YassinHajaj]

Describe the bug

The rendering of a Qute template with specific {#let} or {#set} constructs results in a timeout instead of the expected exception when certain data is missing. The issue occurs when using TemplateInstance combined with data() method calls to pass data to the template.

I attempted to use the data() method to provide the required context for the template, but when the template tried to access a non-existent key, the operation timed out instead of immediately throwing a TemplateException. The issue is particularly evident with nested structures and the use of {#let} and {#set} constructs in Qute templates.

Expected behavior

When rendering a Qute template and a key referenced within the template is missing, the engine should throw a TemplateException with an appropriate message indicating that the key was not found.

For example:

• Rendering error: Key "c" not found in the map with keys [a] in expression {c}

Actual behavior

Instead of throwing a TemplateException, the rendering operation times out with the message:

• rendering timeout [10000ms] occurred.

This happens when using TemplateInstance in combination with either one of those:

• The {#let} construct.
• The {#set} construct.
• A missing {/let} closing tag.

When debugging internally, I can see the exception being thrown in TemplateImpl#renderAsyncNoTimeout

But still, the final exception is the timeout.

How to Reproduce?

Ensure you are using the Quarkus version 3.15.1.

Run the following test class

@QuarkusTest
class QuteTest {

    @Inject
    Engine templateEngine;

    private static final Map<String, Object> DATA = Map.of(
            "a", Map.of("b", Map.of())
    );

    @Test
    void withDataFactoryMethod() {
        TemplateInstance instance = templateEngine.parse("""
                {#let b = a.b}
                    {c}
                {/let}
                """).data(DATA);

        assertThatThrownBy(instance::render)
                .isInstanceOf(TemplateException.class)
                .hasRootCauseMessage("Rendering error: Key \"c\" not found in the map with keys [a] in expression {c}");
    }

    @Test
    void withInstanceThenDataForEachEntry() {
        TemplateInstance instance = templateEngine.parse("""
                {#let b = a.b}
                    {c}
                {/let}
                """).instance();
        for (var e : DATA.entrySet()) {
            instance.data(e.getKey(), e.getValue());
        }
        assertThatThrownBy(instance::render)
                .isInstanceOf(TemplateException.class)
                .hasMessageContaining("rendering timeout [10000ms] occured");
    }

    @Test
    void withSet_withInstanceThenDataForEachEntry() {
        TemplateInstance instance = templateEngine.parse("""
                {#set b = a.b}
                    {c}
                {/set}
                """).instance();
        for (var e : DATA.entrySet()) {
            instance.data(e.getKey(), e.getValue());
        }
        assertThatThrownBy(instance::render)
                .isInstanceOf(TemplateException.class)
                .hasMessageContaining("rendering timeout [10000ms] occured");
    }

    @Test
    void withLetWithoutEndTagwithInstanceThenDataForEachEntry() {
        TemplateInstance instance = templateEngine.parse("""
                {#let b = a.b}
                    {c}
                """).instance();
        for (var e : DATA.entrySet()) {
            instance.data(e.getKey(), e.getValue());
        }
        assertThatThrownBy(instance::render)
                .isInstanceOf(TemplateException.class)
                .hasMessageContaining("rendering timeout [10000ms] occured");
    }
}

Output of uname -a or ver

Darwin

Output of java -version

21.0.1

Quarkus version or git rev

3.15.1

Build tool (ie. output of mvnw --version or gradlew --version)

Apache Maven 3.9.1

Additional information

As you can imagine, this will lead to people investigating timeout issues and exploring timeout solutions instead of focusing on their actual issue.

[quarkus-bot]

/cc @mkouba (qute)

[mkouba]

Thanks for the report!

Indeed, we handle the missing properties inconsistently. For Map (QuteTest#withDataFactoryMethod()) it works as expected. However, for Mapper (all other test methods in the QuteTest) the original exception slips through the error handling and the returned CompletableFuture is never completed - hence the timeout exception.

This pull request should fix the problem: #44682

FTR this issue can only occur if strict rendering is enabled (the default).

[YassinHajaj]

Makes perfect sense, thanks for the quick fix Martin !

[mkouba]

Makes perfect sense, thanks for the quick fix Martin !

You're welcome 🙏