类路径顺序更改时无法启动 main class

Question

I am trying to start rascal with clair from the command line, however I do not understand why this happens:

java -cp "rascal-0.18.0.jar;clair_0.1.0.202005281059.jar;org.eclipse.cdt.core_6.11.0.202003081657.jar" org.rascalmpl.shell.RascalShell
Version: 0.18.0
INFO: detected |lib://rascal| at |jar+file:///C:/ws/rascal-0.18.0.jar!/|
INFO: detected |lib://clair| at |jar+file:///C:/ws/clair_0.1.0.202005281059.jar!/|
rascal>

But when the order of the jars changes, it fails:

java -cp "clair_0.1.0.202005281059.jar;rascal-0.18.0.jar;org.eclipse.cdt.core_6.11.0.202003081657.jar" org.rascalmpl.shell.RascalShell
Version: 0.18.0
INFO: detected |lib://clair| at |jar+file:///C:/ws/clair_0.1.0.202005281059.jar!/|
INFO: detected |lib://rascal| at |jar+file:///C:/ws/rascal-0.18.0.jar!/|
main function should either have one argument of type list[str], or keyword parameters
Usage: java -jar ...

Is this normal behavior with classpaths?

Note: The clair jar does not contain a org.rascalmpl.shell.RascalShell class.

Update: Removing from META-INF/RASCAL.MF the line:

Main-Function: main
Main-Module: lang::cpp::IDE

resolves the problem, so it seems to be an issue with Rascal (and a rascal function) and not with Java (and a Java function).

Answer 1

I think you have found two bugs in the REPL:

1. The second behavior is the bug that we try to run the Main-Function definition which is intended for the IDE plugin, also in the terminal. I think the issue/bug is that we use the same configuration for command line as ide integration point, we might need to add a seperate tag for this.
2. We should provide a way to say which RASCAL.MF we want to run, since now it just picks the first one it sees (rascal also has a RASCAL.MF file).

Answer 2

RascalShell's main function behaves differently if there are commandline parameters and differently depending on the first RASCAL.MF file it finds in the classpath.

• If there is a parameter, then it loads that parameter as a module name and invokes the main function in that module, passing it the other commandline parameters
• Otherwise it starts the REPL
• But : if the first RASCAL.MF file it finds in the classpath has a Main-Module and a Main-Function, then it loads this module always and starts its main function.

I suspect the latter is at work: the order of the classpath changes which RASCAL.MF file is found and therefore the REPL does not start but some module is being loaded and not found. I'm not sure though, since I can't set a breakpoint from here;-)