jextract standalone repository

[Daniel Jarabek]

Hi,

I noticed you are using Gradle as a build tool for jextract. I took a 
look at your build.gradle file and noticed a few things that could be 
improved. I'm by no means a Gradle expert, but I hope my advice is still 
helpful.

1. Use Gradle JVM toolchains
Gradle JVM toolchains let you use JDKs other than the JDK Gradle is 
running on. This would eliminate the need for the jdk18_home property. 
Gradle automatically scans for JDKs matching the requirements in known 
paths as well as user specified locations. Unfortunately, the moditect 
plugin uses java.home to locate tools, however you can still manually 
override this property with the location from the toolchain. The 
jpackage plugin handles toolchains correctly. You can learn more about 
Gradle toolchains here: 
https://docs.gradle.org/current/userguide/toolchains.html

2. Use a more "gradle-like" approach
This is a little bit harder to do. Gradle has advanced features relating 
to incremental builds and caching, however the use of onlyIf with file 
exists checks breaks many of these features, meaning you must run clean 
task before every build to get a fresh build. This could cause some 
confusion for people who are familiar with Gradle's normal operation. 
This isn't really that big of an issue, but might be something to 
consider in the future.

3. General cleanup/improvements
A lot of things could be generally cleaned/improved up, for example:
- `options.compilerArgs.addAll(['--release', '18'])` can become 
`options.release = 18`
- `dependsOn jar` in addMainModuleInfo would be more technically correct 
than `dependsOn build`
- making build task depend on jpackage task so that build (the normal 
gradle task to build a project) creates the executable.
- improvements to libclang path handling are already being worked on at 
https://github.com/openjdk/jextract/pull/8

I would be willing to make pull request(s) for #1 and #3 if those are 
desired changes and if JBS issues can be created.

-DJ

On 3/23/2022 5:50 PM, Maurizio Cimadamore wrote:
> Hi,
> as anticipated in [1], jextract has finally landed in its own standalone 
> repository:
> 
> https://github.com/openjdk/jextract
> 
> The version of jextract included in this repo is suitable to work with 
> Java 18 (just hot off the press!), and we plan to create new branches as 
> new Java versions will come out (to make it easy to find the version you 
> want to work with).
> 
> The jextract sources can be built using gradle; as usual, the build 
> depends on libclang, so a LLVM binary snapshot is required [2]. Testing 
> is also possible (requires jtreg).
> 
> Jextract binary snapshots will be made available at a later date. Moving 
> forward, we will gradually phase out the jextract branch 
> (foreign-jextract) of the panama/foreign repository, and work on the 
> standalone repository instead.
> 
> If you are interested, please give it a try, and let us know what you 
> think.
> 
> Cheers
> Maurizio
> 
> [1] - 
> https://mail.openjdk.java.net/pipermail/panama-dev/2021-December/015895.html 
> 
> [2] - https://releases.llvm.org/download.html
> 
>