We currently use JDK 9 build 109 as our boot JDK to build FX 9, and use a separate Jigsaw JDK to build the javapackager and to run tests in "Jigsaw" mode. We need to upgrade to building with a Jigsaw-aware boot JDK for several reasons.
1) This will remove the restriction in the current upgrade process for the Jigsaw-based JDK used by the packager where we have to disable the packager for one week (this cases all SQE tests to fail and makes the packager unavailable for a week).
2) We cannot use any APIs that have changes since JDK 9 build 109. In some cases we can work around this with reflection, but in some cases we are stuck.
3) We are blocked from fixing any bugs that depend on a newer JDK (e.g., JDK-8157508).
Related to the above, we cannot catch many errors at compile time today; rather we only hit the problems at runtime.
4) Testing in "legacy mode" with jfxrt.jar can mask problems that are introduced (our mitigation for this has been to build the JDK locally and do some testing in "Jigsaw" mode).