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https://issues.apache.org/jira/browse/MJLINK-27?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16634583#comment-16634583
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Gili commented on MJLINK-27:
----------------------------
Karl,
[http://openjdk.java.net/jeps/261] defines an element as a JAR file or a
directory.
{quote}When searching a module path for a module of a particular name, the
module system takes the first definition of a module of that name
{quote}
I want to emphasize this sentence. They wouldn't talk about using the first
match if having multiple modules with the same name always failed.
{quote}if an element of a module path contains definitions of multiple modules
with the same name then resolution fails and the compiler, linker, or virtual
machine will report an error and exit.
{quote}
Let's break this down piece by piece.
* A JAR file cannot contain multiple files with the same path, hence it cannot
contain multiple modules with the same name.
* The only element that may contain multiple modules with the same name is a
directory.
* Hence, if a directory contains multiple modules with the same name then
resolution will fail.
* If multiple JAR files contain a module with the same name, then the first
match on the module path is used.
> Code incorrectly assumes that two modules won't have the same name
> ------------------------------------------------------------------
>
> Key: MJLINK-27
> URL: https://issues.apache.org/jira/browse/MJLINK-27
> Project: Maven JLink Plugin
> Issue Type: Bug
> Affects Versions: 3.0.0-alpha-2
> Reporter: Gili
> Priority: Major
>
> Karl Heinz Marbaise closed MJLINK-7 referencing [a Stackoverflow
> post|https://stackoverflow.com/questions/46573572/java-9-possible-to-have-2-modules-with-same-name-on-module-path/46574200#46574200]
> to prove that module names must be unique. In fact, this Stackoverflow post
> says the exact opposite. The bottom half of the post states that modules in
> separate directories **are** allowed to have the same name. The bottom of the
> post concludes:
> {quote}That makes it possible to have the same module in different
> directories.
> {quote}
> It doesn't have to be the same module per-se. It is possible for two
> different implementations with the same module name to reside on the module
> path, so long as the modules reside in different directory. This is useful
> for "class shadowing". In my particular case, I ship a no-op implementation
> of a module by default but users can insert a working implementation in front
> of the module path to enable the feature.
> Please reopen this issue or continue its work here.
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