As of Resteasy 3.0.14-Final this should be possible:
https://issues.jboss.org/browse/RESTEASY-166
https://docs.jboss.org/resteasy/docs/3.1.0.Final/userguide/html/WADL.html
Add this to your web.xml:
<servlet>
<servlet-name>RESTEasy WADL</servlet-name>
<servlet-class>org.jboss.resteasy.wadl.ResteasyWadlServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>RESTEasy WADL</servlet-name>
<url-pattern>/application.xml</url-pattern>
</servlet-mapping>
I tried this on WildFly 10.1.0 and I had to include an extra library:
Maven artifact: https://javalibs.com/artifact/org.jboss.resteasy/resteasy-wadl
Add the following to your pom.xml:
<!-- https://mvnrepository.com/artifact/org.jboss.resteasy/resteasy-wadl -->
<dependency>
<groupId>org.jboss.resteasy</groupId>
<artifactId>resteasy-wadl</artifactId>
<version>3.0.14.Final</version>
<exclusions>
<exclusion>
<groupId>org.jboss.resteasy</groupId>
<artifactId>resteasy-jaxrs</artifactId>
</exclusion>
</exclusions>
</dependency>
Next re-publish and access the WADL at [context-root]/application.xml