[MCOMPILER-317] Plugin generates wrong modulepath (dependencies listed in wrong order)

**[Gili](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=cowwoc)** opened **[MCOMPILER-317](https://issues.apache.org/jira/browse/MCOMPILER-317?redirect=false)** and commented

Testcase: https://github.com/cowwoc/maven-java9-class-shadowing

If a project contains dependencies with the same module name (which is valid according to https://stackoverflow.com/a/46573805/14731) then maven-compile-plugin invokes `javac` with a modulepath containing dependencies in an (apparently) arbitrary order. If I place the project in one directory, I get one order. If I place the project in another directory, I get another order. This is 100% reproducible across multiple runs, across different computers.

I suspect that somewhere deep inside the code someone is using `HashMap` which is leading to undefined iteration order depending on the path being used.

Expected behavior: dependencies should be listed in the same order as declared in pom.xml (see https://stackoverflow.com/a/793193/14731)

Actual behavior: regardless of whether I list `ExtensionPresent` before or after `MyLibrary`, the wrong order gets passed to `javac`.

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**Affects:** 3.7.0

**Issue Links:**
- [MNG-6357](https://issues.apache.org/jira/browse/MNG-6357) Dependency order should be nearest first

2 votes, 4 watchers

Start with the reproducible project at https://github.com/cowwoc/maven-java9-class-shadowing and compare its declared dependency order with the modulepath passed to javac. Trace the Maven Compiler Plugin dependency-ordering path and verify the result against the expected pom.xml order, while checking the related MNG-6357 issue for context.

Written by the indexing model from the issue text.