It happens occasionally that when I (try to) launch and app by pressing F5, I am greeted with a dialog to the effect that 'Build Failed'. My project looks fine as far as I can tell. There is really no way for me to know what this 'mysterious build' is not happy about. That is a very poor user experience. At least there should be some way to see the root error from this 'build' that was silently run on my behalf, without generating any output whatsoever in any place that I can read it.

Note: having some inkling that the error probably comes from the JDT language server, and having some experience with JDT + m2e in a 'real' Eclipse, I am guessing the problem may be that m2e thinks the 'project model is out of date with the pom'. (This is a common and annoying error we often see as m2e users). Typically you can make it go away by urging m2e to force a project update. So... what I do in vscode, is open up the pom, type some whitespace, and save. Then JDT LS extension will offer to do just that, rebuild project models. Lo and behold... this usually fixes the problem and makes that annoying error go away next time I try to launch.

To be honest, maybe this mess, isn't the fault of the vscode-java-debug plugin (but rather something that maybe jdt.ls should handle better). However, I think it would still be a good idea to add some more information to that annoying dialog (which I presume) vscode-java-debug is popping up.

This, 'the build has failed' dialog is truly infuriating. You are telling me there was an error, but you don't bother telling me what the error actually was? Really?