[BUG] SuperBuilder can cause non-reproducible builds

[Kidlike]

Describe the bug
When using @SuperBuilder in my project, there is some random behavior introduced, on the generated bytecode of classes annotated with @SuperBuilder, which causes the builds to be non-reproducible

To Reproduce
I have tried to create sample projects, but I can't pinpoint the root cause of the issue...

Here is the diffoscope output: diffoscope.txt

From what I have observed, there (at least) 2 key differences:

1. Sometimes Lombok inserts a checkcast instruction, but not always.
2. Sometimes the number/id of the target class is plus or minus 2 between builds (e.g. for invokevirtual)

Version info (please complete the following information):

• Lombok version: 1.18.30
• Platform: Linux, java 17.0.4.1 (but same results with 21.0.1)

Additional context

• https://maven.apache.org/guides/mini/guide-reproducible-builds.html

[janrieke]

This seems to me like a compiler issue. The checkcast diff (in Placement$PlacementBuilder.class) is within the bridge self method. That method is not generated by lombok, but injected by javac to bridge the gap between overridden methods with different return types (covariant return types). In your case, it bridges between protected abstract B self(); and protected BasicCardSuper$BasicCardSuperBuilder self();.

When I compile similar @SuperBuilder classes, I only get the version without checkcast.

Could it be that you are accidently using different compilers?

[janrieke]

Are there any other annotation processors involved?

[janrieke]

There is another weird thing going on: In the lombok-generated constructor Placement(PlacementBuilder<?, ?> b) there also is an additional checkcast before the actual call to the super-constructor. That's weird because it should be statically known to the compiler that this checkcast can never fail. (That additional checkcast is also the reason for the diff in the constant pool.) It seems that the compiler somehow lost the information that PlacementBuilder extends BasicCardSuperBuilder.

[Kidlike]

hey @janrieke, thanks for your interest!

Could it be that you are accidently using different compilers?

Not that I'm aware of. I run this from command line with maven.

Are there any other annotation processors involved?

Yes:

1. lombok
2. mapstruct-processor
3. lombok-mapstruct-binding

Everything is latest version.

I would expect that Mapstruct would not modify my DTOs though... Is that a wrong assumption?