RFR: JDK-8266877: Missing local debug information when debugging JEP-330

[Alan Bateman]

On Sun, 9 May 2021 15:51:29 GMT, Jaroslav Tulach <github.com+26887752+JaroslavTulach at openjdk.org> wrote:

> I am polishing support for [JEP-330](https://openjdk.java.net/jeps/330) in NetBeans ([PR-2938](https://github.com/apache/netbeans/pull/2938)) and I have problems with debugging. Local variables aren't visible as the compiler doesn't pass `-g` option when compiling the main class. I'd like to see 
> 
> ![obrazek](https://user-images.githubusercontent.com/26887752/117578440-a876e000-b0ee-11eb-85b6-3c998f71879f.png)
> 
> however, that requires one to pass `-g` option to the compiler somehow. As far as I can say there is no such way and hence I decided to create this pull request. If I invoke:
> 
> $ java -agentlib:jdwp=transport=dt_socket,address=8000,server=y,suspend=y x.java
> 
> it detects JDWP is on and adds `-g` to the compiler arguments. Is this an acceptable improvement? The alternative is to avoid using JEP-330 when debugging and rather generate `.class` by invoking `javac` and then run it as usual, but I'd rather rely on JEP-330 and avoid creation of the `.class` file.

src/jdk.compiler/share/classes/com/sun/tools/javac/launcher/Main.java line 347:

> 345:                     if (opt.startsWith("-agentlib:jdwp")) {
> 346:                         javacOpts.add("-g");
> 347:                     }

The JDWP agent does expose an agent property for tools for the server=y case but it wouldn't be appropriate for the source launcher to look for that. So checking for a CLI option is probably okay, just needs to be  "-agentlib:jdwp=" to avoid matching other agents prefixed with "jdwp". Also check for "-Xrunjdwp:" too because -Xrun is still used.

-------------

PR: https://git.openjdk.java.net/jdk/pull/3939