Both the wildfly and the wildfly-ee feature packs declare a jaxrs-server layer. Since wildfly is added on top of wildfly-ee, what's in both layer-specs gets applied, so what's in the layer in wildfly FP is basically just an addition over what's in wildfly-ee:

<layer-spec xmlns="urn:jboss:galleon:layer-spec:1.0" name="jaxrs-server">
    <dependencies>
        <layer name="microprofile-rest-client" optional="true"/>
    </dependencies>
</layer-spec>

Note there's nothing in there about the main JAXRS support. That's because the wildfly-ee layer handles that part.

With WF Preview we use the wildfly-preview FP which does not build on wildfly-ee; rather it needs to include everything itself (generally by copying in the source from ee-feature-pack/galleon-shared and using it). But that is broken when it comes to jaxrs-server. There it overrides what comes from ee-feature-pack/galleon-shared, but it forgets to add in the microprofile-rest-client dependency.

This results in the problem istudens@redhat.com describes at https://github.com/wildfly/wildfly/pull/17290/files#r1357983580.

Fix is:

1) Add the missing dep to the wildfly-preview jaxrs-server layer-spec.
2) Move the wildfly-ee jaxrs-server layer-spec from galleon-shared to galleon-local, as it's not actually shared. Same for wildfly FP layer spec.