j2cl-super: A Java repository from xamde

How to deal in j2cl with the absence of super-source. j2cl has no built-in concept of super-sources, just sources.

Using @GwtIncompatible you can write shared code to run on the client and aub-class it with more performant or more feature-rich JVM-only implementations. However, you cannot remove any field or method for the JVM version.

I am big fan of shared code. For me, shared code is a JAR on which I can depend from server-side code in pom.xml and use it. Or I can depend on it from j2cl-client-side code and use the same library. Isn't the beauty of j2cl to have business logic being tested to death in expressive JUnit tests on the server-side and later be used on the client-side? In GWT this was nicely supported via super-source mechanism.

Example

Assume I write a math-library, for being used on client and server side. I am fully aware of j2cl and want to create a compatible library. On the server-side I'd like to use slf4j-api for logging. But when running on the client, I need to super-source the slf4j-api and use a compatible replacement.

NOTE: Deep down, the server side will use System.out.print as a fall-back and the client side will use Console.log instead. A good example is straight from the bazel docs on super-sourcing in j2cl. So somewhere I need to realize this "switch".

The best way I could come up with is:

Fork slf4j-api code and rewrite/annotate for j2cl -> slf4j2cl
math-lib uses slf4j2cl on the client-side
Users of math-lib on the JVM/server-side need to manually exclude slf4j2cl in the pom.xml and include the real slf4j-api instead

   <dependencies>
        <dependency>
		    <artifactId>math-lib</artifactId>
            <exclusions>
                <exclusion>
	                <!-- we want the real deal on JVM, not this j2cl replacement -->
                    <groupId>de.xam.j2cl</groupId>
                    <artifactId>slf4j2cl</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
           <!-- to show j2cl an slf4j api & impl for the client side -->
	       <groupId>org.slf4j</groupId>
           <artifactId>slf4j-api</artifactId>
           <version>1.7.36</version>
        </dependency>
	</dependencies>

Issues:

Users of math-lib need know-how and which dependencies of if to replace with what -- knowledge that would better be kept in math-lib
If the dependency chain gets deeper, every client-side consumer of any dependency using math-lib needs to add the right exclusion & replacement dependencies.

Is there a more elegant (hint: super-source?) way to achieve this goal? Maybe putting some extra info in the pom of math-lib that slf4j2cl dependency should be replaced with slf4j-api dependency?

Maybe these remarks from the j2cl-m-p can be generalized for public use

[INFO] --- j2cl-maven-plugin:0.19-SNAPSHOT:build (default-cli) @ client-app ---
[INFO] Removing dependency com.google.jsinterop:base:jar:1.0.0:compile, replacing with com.vertispan.jsinterop:base:jar:1.0.0-SNAPSHOT

This Repository

math-lib -- a fictive shared library (math is a good example for shared code)
server-app -- a plain old server app using math-lib and log-api
client-app -- a j2cl app using math-lib

xamde/j2cl-super

Example

This Repository