BP_NATIVE_IMAGE=false does not work

[dmikusa]

Expected Behavior

I should be able to set BP_NATIVE_IMAGE=false and it should disable native image builds. This should override any automatic detection that happens in the buildpack.

Current Behavior

If you set BP_NATIVE_IMAGE=false, it is ignored. The buildpack only looks to see if this env variable is set, it does not look at the contents.

Possible Solution

I think fixing this is just a matter of looking at the value and evaluating it as a boolean. Double check the detection process though, and make sure that's sufficient.

Steps to Reproduce

Take a Spring Boot 3.4 application from start.spring.io with Native Image support. Build it with Spring Boot build tools. The build will automatically be a native image build. Now set BP_NATIVE_IMAGE=false. It will be ignored & you'll still get a native image build.

Motivations

In the cases where the buildpack detects that native image builds should occur, a user may want to be able to override this and not have a native image build. User should be able to opt-out.

[HyoKImAbsolut]

same issue

[dmikusa]

The issue here is that native-image is not an optional buildpack in java-native-image, so there's no way to "skip" that buildpack at detect time.

If we treated BP_NATIVE_IMAGE=false as pass=false during detection, what you'd be saying with BP_NATIVE_IMAGE=false is fail my build. I don't think that's the best way to handle that.

What it's doing now is to simply pass detection, even if BP_NATIVE_IMAGE=false. It just does not require native-image-application. That is the issue here though, because spring-boot buildpack will require native-image-application. See here.

Because the buildpack will always pass detection, the build action will always run, so to make BP_NATIVE_IMAGE=false skip the build, we'll need to add logic in it to check if BP_NATIVE_IMAGE=false and not run it's normal build. I've got a PR to do this coming up.

The only drawback of this is that toggling BP_NATIVE_IMAGE=false and then BP_NATIVE_IMAGE=true will throw away the cached layer, so you have to wait for a build again. I don't think there's anything we can do about that though.