Delete stale code when output changes

[MariusVolkhart]

Environment

• JDK version: 19
• Gradle version: 7.4.1
• gradle-jextract version: 0.2.4
• Operating system: MacOs

How does this bug occur?

When the output destination changes, such as when a new className or targetPackage is given, the previously-generated code remains until clean is run.

What happens when the bug occurs?

Compilation proceeds with both the new and the old code.

Would you like to submit a PR fixing this bug?

[ ] YES
[x] NO

[krakowski]

Hey, thanks for your interest in this project!

I'm not entirely sure if this is a bug. Do you experience problems (apart from disk usage) with this behavior? For example, protobuf-gradle-plugin does the same and keeps old classes after changing the .proto files.

• If just className is changed, all generated files belonging to it should be overriden by jextract
• If targetPackage is changed, the source code (i.e. imports) must be updated to reflect this change

Searching the Gradle documentation, I also could not find a way to detect changes in properties during task execution and retrieve the old value. There is InputChanges, however it only works with file properties.

[MariusVolkhart]

No problems, no. Just seemed odd. Honestly, I initially started filing a feature request but then changed to a bug based on how I was phrasing the request. I think it's pretty rare that people change those values after the prototyping stage, so if you say "close, won't implement", I think that's reasonable.

The way I've seen other plugins do this is basically hashing their properties, and writing the files to a directory with the hash as a name. Then, on subsequent runs, they can see if any neighboring directories exist and delete them, since they indicate a different hash.

[MariusVolkhart]

Also, thank you for making and publishing this plugin in the first place! It makes using jextract in a real project a ton easier

[krakowski]

Thanks for your input! I found an (very old) open issue at the protobuf-gradle-plugin repository which discusses a similar topic (google/protobuf-gradle-plugin#33).

The keypoints are:

• Cleaning (i.e. deleting) the output directory could lead to unwillingly deleting other important files if the user specifies another directory than the default one inside the build directory (e.g. src).
• Generated files from a previous task run can be queried using internal Gradle API DefaultTask#getOutputs. Using it in a plugin could result in unexpected behavior in the future.

Since, at the moment, it is only a matter of running gradle clean to delete old source files and deleting whole directories outside the build tree is pretty risky, I would like to go the "close, won't implement" way for now. Although, I'm happy to accept any pull requests solving this issue in a elegant way.

I'm glad this plugin helps other people spinning up projects using jextract! Also, thanks for using it! 🙂