What causes "No foo allowed" in quarkusio/quarkus?

This is intentional test behavior — assert the GraphQL response contains the expected error with data:null instead of treating it as a failure.

quarkusio/quarkus · info · BusinessException

No foo allowed

Error message

No foo allowed

What it means

A BusinessException with message 'No foo allowed' is thrown by the @Mutation 'error' field of the GraphQL GreetingResource. It is a deliberate domain exception used to test how SmallRye GraphQL surfaces business exceptions to clients (error extensions, error classification, exception mappers). It always fires for the default name value 'Foo'.

Source

Thrown at integration-tests/smallrye-graphql/src/main/java/io/quarkus/it/smallrye/graphql/GreetingResource.java:41

    @Query
    public String message() {
        return message;
    }

    @Query
    public Greeting hello() {
        return new Greeting("hello", LocalTime.of(11, 34));
    }

    @Mutation
    public Greetings load(Greetings greetings) {
        return greetings;
    }

    @Mutation
    public String error(@DefaultValue("Foo") String name) throws BusinessException {
        throw new BusinessException("No foo allowed");
    }

    @Name("options")
    public List<Greeting> buildInOptions(@Source Greeting greeting) {
        List<Greeting> options = new ArrayList<>();
        options.add(new Hello());
        return options;
    }

    @Name("options2")
    // make sure that returning Collection.class does not break native mode
    public Collection<Greeting> buildInOptionsCollection(@Source Greeting greeting) {
        List<Greeting> options = new ArrayList<>();
        options.add(new Morning());
        return options;
    }

    @Query

View on GitHub (pinned to e1c734241f)

Solutions

This is intentional test behavior — assert the GraphQL response contains the expected error with data:null instead of treating it as a failure.
If mapping behavior is under test, check the BusinessException @ErrorCode/exception-mapper registration.
For a successful mutation call, use other mutations of the resource (e.g. greetings/load) rather than 'error'.
When testing error payloads, query the errors/extensions fields of the GraphQL response.

Example fix

// before (always throws)
@Mutation
public String error(@DefaultValue("Foo") String name) throws BusinessException {
    throw new BusinessException("No foo allowed");
}
// after (conditional, for manual use)
@Mutation
public String error(@DefaultValue("Foo") String name) throws BusinessException {
    if ("Foo".equalsIgnoreCase(name)) {
        throw new BusinessException("No foo allowed");
    }
    return "Hello " + name;
}

Defensive patterns

Strategy: try-catch

Validate before calling

if ("Foo".equalsIgnoreCase(name)) {
    // this mutation always fails for the default value; expect a GraphQL error response
}

Try / catch

try {
    response = graphQLClient.post(mutation("{ error }"));
} catch (Exception e) {
    // expected: response contains errors[0].message 'No foo allowed' and data.error == null
}

Prevention

Assert on the GraphQL errors/extensions payload rather than HTTP status.
Register and test an exception mapper/@ErrorCode for BusinessException so error shape is stable.
Avoid calling the deliberate 'error' mutation outside of error-mapping tests.
Keep business exceptions typed (BusinessException) so clients can branch on them.

When it happens

Trigger: Executing the GraphQL mutation { error } (or error(name:"Foo")) — the mutation unconditionally throws BusinessException('No foo allowed').

Common situations: Running the smallrye-graphql integration tests, verifying @ErrorCodes/exception-mapper behavior, or manually probing the GraphQL endpoint with the error mutation.

Related errors

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/81b13911d7327bc6. Report an issue: GitHub.