jdtls builds launches with ECJ, which rejects some code javac accepts (for example a generic method call used as an if condition), so such a Maven project could not be run from the IDE. Settings › Build, Execution, Deployment › Maven › Delegate IDE build/run actions to Maven makes Automatic and Build (Make) launches of Maven modules compile with Maven, as Rebuild already did. Classes JDT wrote for sources with errors look up to date to Maven's incremental compiler, so a delegated launch JDT reports errors for recompiles everything and javac's result decides whether it starts. Editor diagnostics still come from jdtls. Off by default.
Co-authored-by: GGVidal <52431033+GGVidal@users.noreply.github.com>