Moduleloading: Fix loading of classes in packages only present as versioned entries

[matthiasblaesing]

The NetBeans classloader infrastructure relies on a mapping of packages
classloaders can load resources/classes from. That mapping is currently
not scanning META-INF/versions/ for packages. This becomes a
problem if the versioned folder contains packages not present in the
non-versioned part of the JAR.

This change adds coverage for the versioned folder.

Closes: #9371

[mbien]

have you tried:

ret = new JarFile(file, false);

->

ret = new JarFile(file, false, JarFile.OPEN_READ, JarFile.runtimeVersion());

and checked if the packages show up automatically when the jdk api is used? This will open the jar in multi release mode, default is jdk8 mode.

[matthiasblaesing]

I thought briefly about using the JarFile support, but what I see is, that there is code in JarClassLoader already dealing specially with the version directories. Switching to the versioned JarFile constructor would mean, that these codepaths have to be revisited. What is more JarClassLoader not only ties into JarFile, but also Archive. Archive is not version aware, so we would have two different views.

[matthiasblaesing]

As I have to assume I won't get a quick test of the fix (#9371 (comment)), I created my own reproducer:

• Demo Library having a single class eu.doppelhelix.test.multireleasesample.Demo that returns the target version via getVersion. The project has a base implementation (target 8) and the real reproducer for 21, that also contains an implemenation in another package, only present in the 21 versioned directory. multireleaseloading.zip
• A module that calls into the library (Mainmenu -> View -> Dump Version)
  multireleasesample.zip

Assuming the sample is run on JDK 21+, with a build from master you get:

With this PR the result is the expected: