Use jnr-posix-api plugin

[basil]

This PR switches this plugin to depend on the newly-released jnr-posix-api plugin rather than getting JNR from core. Once this is merged and released, and once enough users have upgraded to this release, we can consider removing the JNR dependency from core.

CC @daniel-beck @Wadeck

[daniel-beck]

If the plugin isn't detached, wouldn't it make more sense to use a different package than hudson.os? How confident are we about classloading correctness, potentially involving dynamically loaded plugins, when classes are in core and a plugin?

[basil]

How confident are we about classloading correctness, potentially involving dynamically loaded plugins, when classes are in core and a plugin?

I haven't done an end-to-end test but I'm pretty confident. I added

https://github.com/jenkinsci/jnr-posix-api-plugin/blob/fbb90b6ad669feef44cd5bcf548b8080d1e5c9d7/pom.xml#L70

to jnr-posix-api-plugin and did some testing in the script console to make sure the class loading worked as expected with both older and newer cores. Once the baseline is updated to a core that includes jenkinsci/jenkins#5979 I plan to remove everything except org.objectweb.asm. from that line.

In terms of pam-auth specifically, it doesn't have a <maskClasses> entry, so it will find the class from core right now, and once jenkinsci/jenkins#5979 is merged and released it'll fail to find it in core and then look in the plugin's class loader and find it there through jnr-posix-api-plugin. So there should be no problem.

[basil]

Any next steps for moving forward with this?

[basil]

@daniel-beck @Wadeck ?

[jglick]

it doesn't have a <maskClasses> entry, so it will find the class from core right now

I guess there is no chance of using RealJenkinsRule due to the problem of mocking out PAM?

[jglick]

Sounds OK. (I apparently have GH write access, but not Artifactory access.)

[basil]

@daniel-beck @Wadeck Gentle ping.

[daniel-beck]

I see this updates a bundled JNA, probably due to the core dependency update and presence in the core BOM. Does this library need to be bundled here, or can we just use whatever is in core?

[basil]

Does this library need to be bundled here, or can we just use whatever is in core?

JNA does not need to be bundled here, nor is it used at runtime in production because core provides JNA already. In any case this is a pre-existing issue not related to this PR.