adding sort option for build-classpath

[rmannibucau]

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For now it is a proposal since jira status is quite weird regarding that but I fail to see how to have a deterministic build without such an option so proposing a solution and will create tickets if there is an agreement on the solution.

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[michael-o]

What is the benefit? The same request keeps popping up with Tomcat and the classpath does not rely on order.

[rmannibucau]

@michael-o well you should consider these points:

1. if not sorted then nothing is reproducible in java world so the build-classpath mojo requires a postprocessor or replacement for all consumer of the output (downstream mojo, custom runtime code etc) - including a java -cp @<cp from build-classpath> MyMain kind of commands or jib based builds or CDS archive build ...
2. tomcat has solutions for that - mainly custom webapploader/classloader or OS specific stuff - even if tomcat itself does not want to do the integration out of the box for the same reason so even if the project rejects the features some users rely on it

I'm not 100% sure if we need more flexibility on the ordering but not sorting the output is quite useless for any pipeline relying on the classpath dump (it is fine for other use cases) so hope we can find a way to sort somehow whatever the order is.

Hope it makes sense.

[michael-o]

For debug purposes I understand that a canonization makes sense, but bit for the actual class path. That should always work.

[rmannibucau]

Classpath is a sorted list in the jvm so order is important for classes and resources. Custom classloaders are unrelated to the classpath and dont have to respect that even if all "true" urlclassloaders will. But here we speak of classpath so order is a thing.

[michael-o]

Classpath is a sorted list in the jvm so order is important for classes and resources. Custom classloaders are unrelated to the classpath and dont have to respect that even if all "true" urlclassloaders will. But here we speak of classpath so order is a thing.

Ordered != sorted. Where is is sort? Show me!