Editing classpath file requires restart of VS Code

Originally created by @VanessaLange at Microsoft/vscode-java-debug#576

When adding a jar to the classpath file the program won't build any longer and you get the error message: "Build failed, do you want to continue?" You have to restart VS Code before it works again.

Environment

• Operating System: macOS Mojave Version 10.14.4 (also Windows 10)
• JDK version: openjdk version "1.8.0_212"
• Visual Studio Code version: 1.33.1
• Java extension version: 0.43.0
• Java Debugger extension version: 0.17.0

Steps To Reproduce

1. Create a new Java Project
2. Add a jar to the classpath
3. Try to run the program

Current Result

The build fails and you cannot run the program.

Expected Result

Either building works out of the box when editing the classpath or at least we get a message that restarting VS Code is required.

Additional Informations

The language server is loaded correctly (thumbs up icon).

Riproduci il malfunzionamento in un nuovo Java Project aggiungendo un jar al classpath ed eseguendo il programma in VS Code. Traccia il modo in cui la Java extension gestisce le modifiche al classpath e lo stato della build; il lavoro è completato quando il progetto viene compilato ed eseguito senza riavviare VS Code, oppure segnala chiaramente quando è necessario un riavvio.