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From "Marcel Kolsteren (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MCOMPILER-321) Problematic Java 9 modules are silently ignored
Date Sat, 27 Jan 2018 20:26:00 GMT

    [ https://issues.apache.org/jira/browse/MCOMPILER-321?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16342297#comment-16342297
] 

Marcel Kolsteren commented on MCOMPILER-321:
--------------------------------------------

Thanks for the quick response!

True, the error that the Java compiler gives is correct, but I'd expect that the maven-compiler-plugin
itself reports the error (and maybe even stops so that the Java compiler is not called at
all).

Regarding the problem with the java modules: that might be solved by using the method {{ModuleFinder#ofSystem​}}.

> Problematic Java 9 modules are silently ignored
> -----------------------------------------------
>
>                 Key: MCOMPILER-321
>                 URL: https://issues.apache.org/jira/browse/MCOMPILER-321
>             Project: Maven Compiler Plugin
>          Issue Type: Bug
>            Reporter: Marcel Kolsteren
>            Priority: Major
>         Attachments: maven-compiler-plugin-bug.zip
>
>
> Before the compilation starts, the compiler plugin prepares the module path and the class
path. Unfortunately, this process is very lenient. If the plugin cannot find a module that
is specified in the module-info file, it doesn't report this problem, and it just carries
on. In the end, the compiler will give a "module not found", giving no clue about the root
cause.
> As an example, I attached a simple maven project with a module info file that refers
to an automatic module named {{jython-standalone}}. The dependencies contain a jar file {{jython-standalone-2.7.0.jar}}.
That jar file contains no module information, and it would normally be resolvable as an automatic
module. However, when building the project, the Java compiler fails with this error:
> {{module not found: jython.standalone}}
> The root cause of the error is that the jar file contains a class at top level, which
is illegal for a module. So, the error message "module not found" is misleading.
> I think this is a bug, because the maven-compiler-plugin fails to perform its task of
building a correct module path, but doesn't tell, and just carries on. Instead, it should
stop, and give an informative error message.
> Relevant source code:
> * [https://github.com/apache/maven-compiler-plugin], class {{CompilerMojo}}
> * [https://github.com/codehaus-plexus/plexus-languages], class {{LocationManager}} and
{{MainClassModuleNameExtractor}}
> * [https://docs.oracle.com/javase/9/docs/api/java/lang/module/ModuleFinder.html]
> The {{MainClassModuleNameExtractor}} uses the {{ModuleFinder}} class of the JDK to find
modules. I think that these two error situations should lead to an error and a clear description
of possible causes:
> * {{ModuleFinder#findAll}} returns an empty set.
> * {{ModuleFinder#findAll}} results in a {{FindException}}. When this happens is well
documented in the {{ModuleFinder#of}} method. This exception is currently swallowed.



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