Using a custom ParamConverter fails when not sending that parameter with the request

[michelcouto]

Describe the bug

When using a custom ParamConverter, the call fails when we do not sending any value for that parameter in the request.

Expected behavior

The request would be executed

Actual behavior

A 404 error happens due to a NPE.

How to Reproduce?

Take this example code:

@GET
    @Path("/greet")
    public Response greet(@QueryParam("number") @Parameter(allowEmptyValue = true) Optional<Integer> numberOpt) {
        if (numberOpt.isPresent()) {
            Integer number= numberOpt.get();
            if (number == null) {
                return Response.ok("Hello! You provided an empty number.").build();
            } else {
                return Response.ok("Hello, " + number+ "!").build();
            }
        } else {
            return Response.ok("Hello, world! No number was provided.").build();
        }
    }

This is the converter:

public class OptionalIntegerParamConverter implements ParamConverter<Optional<Integer>> {

	@Override
    public Optional<Integer> fromString(String value) {
		if (value == null) {
			return null;
		}
		
        if (value.trim().isEmpty()) {
        	return Optional.empty();
        }
        
        try {
        	int parsedInt = Integer.parseInt(value);
        	return Optional.of(parsedInt);
        } catch (NumberFormatException e) {
            throw new IllegalArgumentException("Invalid integer value");
        }
    }
    @Override
    public String toString(Optional<Integer> value) {
    	if (!value.isPresent()) {
    		return null;
    	}
    	
    	Integer intValue = value.get();
        if (intValue == null) {
            return null;
        } else {
            return intValue.toString();
        }
    }

}

}

And this is its provider:

@Provider
public class OptionalIntegerParamConverterProvider implements ParamConverterProvider {
    @SuppressWarnings("unchecked")
	@Override
    public <T> ParamConverter<T> getConverter(Class<T> rawType, Type genericType, Annotation[] annotations) {
    	if (rawType.equals(Optional.class)) {
            if (genericType instanceof ParameterizedType) {
                ParameterizedType parameterizedType = (ParameterizedType) genericType;
                Type[] typeArguments = parameterizedType.getActualTypeArguments();
                if (typeArguments.length == 1 && typeArguments[0].equals(Integer.class)) {
                    return (ParamConverter<T>) new OptionalIntegerParamConverter();
                }
            }
        }
        
        return null; // return null if no converter is needed for the type
    }
}

If that is setup, then trying to call the service without providing any value to the number parameter will fail within RuntimeResolvedConverter

public Object convert(Object parameter) {
        if (runtimeConverter != null)
            return runtimeConverter.fromString(parameter.toString());
        return quarkusConverter.convert(parameter);
    }

it fails because parameter is null.

If I provide no conversion, then it fails only when checking the Send empty value, since "" cannot be converted to an Optional

Thus, a simple change in RuntimeResolvedConverter would fix this:

public Object convert(Object parameter) {
        if (runtimeConverter != null)
            return runtimeConverter.fromString(parameter != null ? parameter.toString() : null);
        return quarkusConverter.convert(parameter);
    }

Output of uname -a or ver

No response

Output of java -version

No response

Quarkus version or git rev

No response

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

No response

Additional information

No response

[quarkus-bot]

/cc @FroMage (resteasy-reactive), @geoand (resteasy-reactive), @stuartwdouglas (resteasy-reactive)

[geoand]

Thanks for reporting!

As you've already done an analysis on the code, would you like to open a Pull Request with the proposed change?
Ideally, a test would also be included.

Thanks

[michelcouto]

Hi!

I have openned a Pull Request with the fix, and also some related tests:
#40311

Since this is the first time I am contributing here, I am not sure that my tests were added correctly...
Please review.

[geoand]

Thanks!

I will check on Monday