[rest-client] @RestForm does not work with a Map

[PierreBtz]

Describe the bug

Using @RestForm with a Map<String,String> fails with the following message: java.lang.IllegalStateException: Form element 'org.acme.rest.client.ExtensionsService.postFilter' could not be converted to 'String' for REST Client interface 'org.acme.rest.client.ExtensionsService'. A proper implementation of 'jakarta.ws.rs.ext.ParamConverter' needs to be returned by a 'jakarta.ws.rs.ext.ParamConverterProvider' that is registered with the client via the @RegisterProvider annotation on the REST Client interface.

Expected behavior

It should be possible to annotate a Map<String, String> (or Map<T,T> with T following the contract of the FormParam javadoc) with @RestForm.

Note: I'm aware that Map itself doesn't follow the contract but according to the rest client quickstart, this should be supported.

Actual behavior

When writing something like:

   @POST
    @Consumes(MediaType.APPLICATION_FORM_URLENCODED)
    Set<Extension> postFilter(@RestForm Map<String, String> filter);

I observe:

java.lang.IllegalStateException: Form element 'org.acme.rest.client.ExtensionsService.postFilter' could not be converted to 'String' for REST Client interface 'org.acme.rest.client.ExtensionsService'. A proper implementation of 'jakarta.ws.rs.ext.ParamConverter' needs to be returned by a 'jakarta.ws.rs.ext.ParamConverterProvider' that is registered with the client via the @RegisterProvider annotation on the REST Client interface.
	at org.acme.rest.client.ExtensionsService$$QuarkusRestClientInterface.postFilter(Unknown Source)
	at org.acme.rest.client.ExtensionsService$$CDIWrapper.postFilter(Unknown Source)
	at org.acme.rest.client.ExtensionsService$$CDIWrapper_ClientProxy.postFilter(Unknown Source)
	at org.acme.rest.client.ExtensionsResource.postFilter(ExtensionsResource.java:44)
	at org.acme.rest.client.ExtensionsResource$quarkusrestinvoker$postFilter_f150e3b45248e706abefa90223a2969c9c2ba0d0.invoke(Unknown Source)
	at org.jboss.resteasy.reactive.server.handlers.InvocationHandler.handle(InvocationHandler.java:29)
	at io.quarkus.resteasy.reactive.server.runtime.QuarkusResteasyReactiveRequestContext.invokeHandler(QuarkusResteasyReactiveRequestContext.java:141)
	at org.jboss.resteasy.reactive.common.core.AbstractResteasyReactiveContext.run(AbstractResteasyReactiveContext.java:147)
	at io.quarkus.vertx.core.runtime.VertxCoreRecorder$14.runWith(VertxCoreRecorder.java:635)
	at org.jboss.threads.EnhancedQueueExecutor$Task.doRunWith(EnhancedQueueExecutor.java:2516)
	at org.jboss.threads.EnhancedQueueExecutor$Task.run(EnhancedQueueExecutor.java:2495)
	at org.jboss.threads.EnhancedQueueExecutor$ThreadBody.run(EnhancedQueueExecutor.java:1521)
	at org.jboss.threads.DelegatingRunnable.run(DelegatingRunnable.java:11)
	at org.jboss.threads.ThreadLocalResettingRunnable.run(ThreadLocalResettingRunnable.java:11)
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
	at java.base/java.lang.Thread.run(Thread.java:1583)

How to Reproduce?

• Checkout the rest client quickstart

• Modify the https://github.com/quarkusio/quarkus-quickstarts/blob/main/rest-client-quickstart/src/main/java/org/acme/rest/client/ExtensionsResource.java class and add:

    @POST
    @Path("/test")
    public Set<Extension> postFilter() {
        return extensionsService.postFilter(Map.of("hello", "world"));
    }

• Modify the https://github.com/quarkusio/quarkus-quickstarts/blob/main/rest-client-quickstart/src/main/java/org/acme/rest/client/ExtensionsService.java class and add:

    @POST
    @Consumes(MediaType.APPLICATION_FORM_URLENCODED)
    Set<Extension> postFilter(@RestForm Map<String, String> filter);

• Start the application: mvn quarkus:dev

• Trigger the problematic code: curl -X POST http://localhost:8080/extension/test

Output of uname -a or ver

Darwin *** 23.6.0 Darwin Kernel Version 23.6.0: Wed Jul 31 20:49:39 PDT 2024; root:xnu-10063.141.1.700.5~1/RELEASE_ARM64_T6000 arm64

Output of java -version

openjdk version "21.0.4" 2024-07-16 LTS OpenJDK Runtime Environment Temurin-21.0.4+7 (build 21.0.4+7-LTS) OpenJDK 64-Bit Server VM Temurin-21.0.4+7 (build 21.0.4+7-LTS, mixed mode)

Quarkus version or git rev

3.15.1

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

Apache Maven 3.9.6 (bc0240f3c744dd6b6ec2920b3cd08dcc295161ae) Maven home: /Users/***/.asdf/installs/maven/3.9.6 Java version: 21.0.4, vendor: Eclipse Adoptium, runtime: /Users/pierrebeitz/.asdf/installs/java/temurin-21.0.4+7.0.LTS Default locale: en_FR, platform encoding: UTF-8 OS name: "mac os x", version: "14.7", arch: "aarch64", family: "mac"

Additional information

No response

[quarkus-bot]

/cc @cescoffier (rest-client), @geoand (rest-client)

[PierreBtz]

Attaching a patch to simplify the reproduction.

gh-43784.patch

[PierreBtz]

Thanks for the fast fix!

[geoand]

👌