Support different agent modes in the native-image Gradle plugin

[gradinac]

This PR reworks agent support by decoupling the agent task instrumentation from image building and introduces the concept of agent modes.

[melix]

The changes look good to me, great work @gradinac ! So I think what's missing now is test coverage and documentation of the breaking changes. Potentially we could document the different agent modes too. I guess you'll have to discuss with @alvarosanchez for the Maven support to be added (fine if the Gradle plugin supports it first).

[melix]

this should probably live under AgentOptions

[gradinac]

I agree, I've moved this to AgentOptions and renamed it to metadataCopy to remain consistent with the naming of other tasks

[melix]

Will need to remove this from draft PR

[gradinac]

Ah yes, I've kept this to make it easier to test locally on multiple machines, I will remove all changes related to local testing

[melix]

This is looking good, let's get this to the finish line!

[melix]

This should be @Internal, it's not an input in the sense of task inputs.

[gradinac]

That's a good point, I'll change it to @Internal

[melix]

This is the last remaining issue AFAICT.

[gradinac]

Snap, sorry for that, I missed this when refactoring, will push an updated version

[melix]

Should probably be a ListProvider or, even better, a ConfigurableFileCollection

[gradinac]

Hmm, we could introduce a ListProperty, but we would manually have to instantiate it and pass it around. We could also go with a ConfigurableFileCollection, though in this context these files are either passed in from a task input, or created internally by mapping another property

[gradinac]

Here's how they are created in this case: https://github.com/graalvm/native-build-tools/pull/230/files#diff-3ca19e7e49fe64feca3a1e88279c961b56e03450666583025c711da44cfb73bbR614-R615

[melix]

Let's keep it as is for now, I'll take a look when I have time

[melix]

Should be removed

[gradinac]

I agree, I will remove everything related to local testing from the PR

[melix]

Given that the "conditional" mode is the recommended mode for libraries, I wonder if we should make it the default when the java-library plugin is applied?

[gradinac]

Given that the "conditional" mode is the recommended mode for libraries, I wonder if we should make it the default when the java-library plugin is applied?

That's a good point - we could do this if the agent mode is not explicitly set on the command line and the user has not specified a `defaultMode in the DSL.

I've noticed plugins behave very similar to tasks in terms of lazyness - there's a withType call that's called back only when a plugin actually executes. For the agent, we hook into project evaluation so I don't think we can use that mechanism.
The alternative is to simply check if the JavaLibraryPlugin is included in the project.

One downside of doing this would be non-apparent changes in the build configuration that depend on included plugins

[melix]

mmm, not sure I follow you. You can do:

project.getPlugins().withType(JavaLibraryPlugin.class) { configure agent convention }

[gradinac]

mmm, not sure I follow you. You can do:

project.getPlugins().withType(JavaLibraryPlugin.class) { configure agent convention }

Ah yes, this would set the convention, but that's the bit i'm unsure about - would this execute before or after project evaluation?

[melix]

It would execute as soon as the java-library plugin is applied. That is to say immediately if it's already applied when this code executes, or later if it's not yet applied.

[gradinac]

It would execute as soon as the java-library plugin is applied. That is to say immediately if it's already applied when this code executes, or later if it's not yet applied.

Makes sense, thank you! :) I'll push an update to the PR