[MCOMPILER-291] No possible use compilerArgs arg "-J--add-opens" multiple times

**[Pascal Schumacher](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=pascalschumacher)** opened **[MCOMPILER-291](https://issues.apache.org/jira/browse/MCOMPILER-291?redirect=false)** and commented

I'm trying to a project with uses lombok to work with java 9.

```

org.apache.maven.plugins
maven-compiler-plugin
3.6.1

1.8
1.8
true

-J--add-opens-Jjdk.compiler/com.sun.tools.javac.processing=ALL-UNNAMED
-J--add-opens-Jjdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED
-J--add-opens-Jjdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED
-J--add-opens-Jjdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED
-J--add-opens-Jjdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED
-J--add-opens-Jjdk.compiler/com.sun.tools.javac.model=ALL-UNNAMED
-J--add-opens-Jjdk.compiler/com.sun.tools.javac.comp=ALL-UNNAMED
-J--add-opens-Jjdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED
-J--add-opens-Jjdk.compiler/com.sun.tools.javac.parser=ALL-UNNAMED

```

```
mvn -X compile
``` shows me that the
```-J--add-opens
``` arguments are collapsed:

```

cmd.exe /X /C ""C:\Program Files\Java\jdk-9\bin\javac.exe" `@C`:/Users/User/random-beans/random-beans/target/classes/org.codehaus.plexus.compiler.javac.JavacCompiler9403484282707867963arguments -J--add-opens -Jjdk.compiler/com.sun.tools.javac.processing=ALL-UNNAMED -Jjdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED -Jjdk.compiler/com.sun.tools.javac.code=ALL-UNNAMED -Jjdk.compiler/com.sun.tools.javac.main=ALL-UNNAMED -Jjdk.compiler/com.sun.tools.javac.tree=ALL-UNNAMED -Jjdk.compiler/com.sun.tools.javac.model=ALL-UNNAMED -Jjdk.compiler/com.sun.tools.javac.comp=ALL-UNNAMED -Jjdk.compiler/com.sun.tools.javac.file=ALL-UNNAMED -Jjdk.compiler/com.sun.tools.javac.parser=ALL-UNNAMED"

```

which results in:

```

Error: Main Class jdk.compiler.com.sun.tools.javac.util=ALL-UNNAMED could not be found or load

```
```

---

**Affects:** 3.6.1

6 votes, 6 watchers

Start by tracing how the Maven compiler plugin handles the repeated compilerArgs entries shown in the issue, then reproduce the behavior with `mvn -X compile` on Java 9. Done means repeated `-J--add-opens` options remain correctly paired with their values so the compilation command no longer treats a later option as a main class.

Written by the indexing model from the issue text.