Make UnionPath behave as paths from ZipFileSystem do.

[noeppi-noeppi]

This changes the behaviour of union paths to match the behaviour from zip paths. To ensure this, all path tests are first run against a zip file system and it is asserted that they don't fail.

This will most likely break modlauncher and forge

Also the tests for the relativize method were moved from TestUnionFS to TestUnionPath.

[noeppi-noeppi]

I did some fixes to the Jar class so it works with the changes from this pull request now. There may be more things in securejarhandler that break with these changes though. Trying to run forge (in a forgedev environment) with this now results in the following exception:

Exception in thread "main" java.lang.NullPointerException: Cannot invoke "java.nio.file.Path.toString()" because the return value of "java.nio.file.Path.getFileName()" is null
	at MC-BOOTSTRAP/cpw.mods.modlauncher@9.1.3/cpw.mods.modlauncher.util.ServiceLoaderUtils.lambda$fileNameFor$2(ServiceLoaderUtils.java:50)
	at java.base/java.util.Optional.map(Optional.java:260)
	at MC-BOOTSTRAP/cpw.mods.modlauncher@9.1.3/cpw.mods.modlauncher.util.ServiceLoaderUtils.fileNameFor(ServiceLoaderUtils.java:50)
	at MC-BOOTSTRAP/cpw.mods.modlauncher@9.1.3/cpw.mods.modlauncher.LaunchPluginHandler.lambda$new$2(LaunchPluginHandler.java:50)
	at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197)
	at java.base/java.util.HashMap$EntrySpliterator.forEachRemaining(HashMap.java:1850)
	at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509)
	at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
	at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:575)
	at java.base/java.util.stream.AbstractPipeline.evaluateToArrayNode(AbstractPipeline.java:260)
	at java.base/java.util.stream.ReferencePipeline.toArray(ReferencePipeline.java:616)
	at java.base/java.util.stream.ReferencePipeline.toArray(ReferencePipeline.java:622)
	at java.base/java.util.stream.ReferencePipeline.toList(ReferencePipeline.java:627)
	at MC-BOOTSTRAP/cpw.mods.modlauncher@9.1.3/cpw.mods.modlauncher.LaunchPluginHandler.<init>(LaunchPluginHandler.java:51)
	at MC-BOOTSTRAP/cpw.mods.modlauncher@9.1.3/cpw.mods.modlauncher.Launcher.<init>(Launcher.java:64)
	at MC-BOOTSTRAP/cpw.mods.modlauncher@9.1.3/cpw.mods.modlauncher.Launcher.main(Launcher.java:77)
	at MC-BOOTSTRAP/cpw.mods.modlauncher@9.1.3/cpw.mods.modlauncher.BootstrapLaunchConsumer.accept(BootstrapLaunchConsumer.java:26)
	at MC-BOOTSTRAP/cpw.mods.modlauncher@9.1.3/cpw.mods.modlauncher.BootstrapLaunchConsumer.accept(BootstrapLaunchConsumer.java:23)
	at cpw.mods.bootstraplauncher@1.0.0/cpw.mods.bootstraplauncher.BootstrapLauncher.main(BootstrapLauncher.java:149)

[SizableShrimp]

The specific crash provided uses an optional chain that defaults to the string "MISSING FILE". It would be good to investigate what the change from "" empty string to "MISSING FILE" would look like for consumers of ServiceLoadersUtils#fileNameFor. And if a null path should count as empty string still or "MISSING FILE".

[marchermans]

Testing procedure is setup and completed.
Last call for this PR before I merge it in a couple of days.

The additional endpoint in #20 mentioned to get the proper paths of a mod needs to be added later.

[cpw]

I suspect that the performance tweaks have completely invalidated this PR. Can you re-evaluate if this is still appropriate?

[noeppi-noeppi]

I just merged the tests from this PR (which assert that UnionPath behaves the same as JarPath) with the performance tweaks and some of them still fail. So yes, it is still appropriate, ill update it to resolve the conflicts.

[cpw]

@marchermans is this still relevant??

[marchermans]

Not that I know of
@noeppi-noeppi ? You ran those tests before.

[noeppi-noeppi]

If it is still relevant to mimic the behaviour of ZipFileSystem, then yes. The UnionPath still behaves different than ZipPath. So if Lex statement here is still relevant, so is this PR.

[MelanX]

This PR is included in the 1.19 milestone. I guess that means it’ll be merged right before 1.19, right?
In just two weeks, 1.21 releases. I think, it’s a bit late.