query parameter as Optional<String> within declarative HttpClient

[krasv]

Hi, is there a limitation not using java Optional as HttpClient parameter?

having the client declared as

@Client("/path")
public interface MyClient {
  @Get("/data")
  @Produces({"application/json"})
  HttpResponse<Data> getData(
      @Nonnull
      @QueryValue(value="param")
      Optional<String> param
  );
}

and invoking the client as such

   Data data = client.getData(Optional.of("paramValue"));

produces at the outbound request the string representation of the Optional instance instead of the optional value.

GET /path/data?param=Optional[paramValue]

The conversion is fixed set to String within the DefaultBinderRegistry see

micronaut-core/http-client-core/src/main/java/io/micronaut/http/client/bind/DefaultHttpClientBinderRegistry.java

Line 81 in b3eaf53

conversionService.convert(value, ConversionContext.STRING.with(context.getAnnotationMetadata()))

Is there either a reason not supporting Optional<String> or is there a way to add a custom binder like https://docs.micronaut.io/latest/guide/index.html#customArgumentBinding for such common data types?

Thanks in advance,
Sven

[graemerocher]

Seems to be the case, although if you speak to the designers of the Optional type they say it should only really be used in return types

[krasv]

Thanks, got another response into that direction too: https://rules.sonarsource.com/java/tag/clumsy/RSPEC-3553

[krasv]

Just got another hint: version 2.2.2 addresses exact that issue: #4568