feat: install multiple JDKs with same major version

[quintesse]

Fixes #2118

[maxandersen]

Interesting. How's it to be used/managed? Couldn't spot clearly the user impact if any?

[quintesse]

The idea is that user impact at first is as close to zero as possible. Mainly to detect if the new system causes any backward compatibility issues.

For the user that is accustomed to installing jdks with jbang jdk install N nothing changes. That command keeps working as before, as does uninstall.

What does change is how jdks are stored on disk. Before you'd just have a bunch of numbered directories in ~/.jbang/cache/jdks, each one containing the jdk for that version, eg:

$ ls -F ~/.jbang/cache/jdks
11/  17/  21/  24/  25/  8/

But now with the new devkitman version you could see this:

$ ls -F ~/.jbang/cache/jdks
11/  17/  21/  24/  25/  26@  26-ea+21-temurin-jbang/  8/

As you can see I just installed a new version 26. And it gets stored in a directory with a full name (its id) and additionally a symlink was created with the name "26" that points to the actual directory.

This symlink serves two purposes: a) is serves as the "default" for that version, so if you have multiple version 26 jdks installed this symlink will point to your "preferred 26 version" and b) it maintains backward compatibility with older JBang versions that will only see the symlinks (older JBang versions ignore directories whose names are not integers).

I still have to make a couple of changes before explaining what else has changed. I will keep you posted in follow-up messages here.

[maxandersen]

gotcha.

and i assume its fine but just asking to know if some limits - on windows the symbolic linking also works ? no extra rights needed etc? in past we "survived" these even without extra rights as jsut one folder but i know some stuff improved here i just forget which :)

And wouldn't it be nicer if stored per vendor?, i.e. / ? or even to simplify have /installs//? just suggesting this to not mix-n-match too much in one folder directly.

whats the signficance of "-jbang" in the name?

[quintesse]

on windows the symbolic linking also works ?

JBang already needs those to work. The default jdk that gets added to your path is a link (a Junction to be precise).

And wouldn't it be nicer if stored per vendor?, i.e. / ? or even to simplify have /installs//? just suggesting this to not mix-n-match too much in one folder directly.

I'm just somewhat following what I see others do. I also think it makes file/folder management slightly more complex to have more levels of directories. Given the fact that nobody should be looking directly at that folder and definitely not depend on its names and structure I feel it's okay to do it this way.

whats the signficance of "-jbang" in the name?

It's because the jdks are managed by the "jbang" provider. There's other providers that can create folders there, for example links to external jdks are handled by the "linked" provider and marked with "-linked".

[quintesse]

@maxandersen this is now ready for review and devkitman 0.4.0 has been released so you don't need to build that to be able to test this PR.

Given the fact that this is a pretty major change it must be tested quite well (I already did of course, but I might be "blind" to certain issues). It must also be tested that older JBang versions keep working even when newer JDKs get installed by this new version.

Also, the workings and output of some of the jdk commands (eg jdk list) have changed somewhat, we might still want to polish that.

[quintesse]

NB: currently releasing 0.4.1 because of a test failure that only appeared when running JBang's GH CI. (Seems GH uses legacy DOS paths in their environment variables, eg. JAVA_HOME=C:\PROGRA~1\Java\jdk11, which devkit handles okay enough except when trying to match it against a modern path)

[maxandersen]

Should I ignore or honor the "do not merge" message ? :)

[quintesse]

Sorry, this PR is ready for review but not ready to merge, I put it back to draft to make that clear.
Any changes I make are to make sure all tests pass and to add some new tests to make sure more things are covered.
But for review purposes (by you) the PR should be good.

[quintesse]

Ok, I marked this PR ready for review again because everything works now. The integration tests are failing because of the Alpine test not being able to download the Jdk 17 it needs, but that's unrelated to this PR.