[jira] [Updated] (MCOMPILER-510) NullPointerException when using --patch-module compiler argument

["Artem K. (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/MCOMPILER-510?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Artem K. updated MCOMPILER-510:
-------------------------------
    Description: 
h2. Summary

When using {{--patch-module}} compiler argument, there is a {{NullPointerException}} due to field {{pathElements}} not being initialized in {{{}CompilerMojo{}}}.
h2. Description

The method {{preparePaths}} in {{CompilerMojo}} has two code paths:
{code:java}
@Override
protected void preparePaths( Set<File> sourceFiles )
{
    boolean hasModuleDescriptor = false;
    // ...
    if ( hasModuleDescriptor )
    {
        modulepathElements = new ArrayList<>( compilePath.size() );
        classpathElements = new ArrayList<>( compilePath.size() );
        pathElements = new LinkedHashMap<>( compilePath.size() );
    }
    else
    {
        classpathElements = new ArrayList<>();
        modulepathElements = Collections.emptyList();
        // ...
    }
}{code}
Notice that in the else part, {{pathElements}} is not initialized. This field is used when the compiler arguments contain {{--patch-module}} switch. So whenever the compiler is used with this switch and there is no module descriptor in the project, NPE occurs.
h2. Proof-of-concept

Attached is a simple proof-of-concept to illustrate the issue. The project consists of a single class with raises {{NullPointerException}} using a new constructor {{{}NullPointerException(Throwable){}}}, which does not exist in base JDK.
 * When executing {{{}javac{}}}{{{{}} src\main\java\poc\Main.java{}}}, the compilation fails as expected.
 * Using a replacement {{NullPointerException}} class in {{java_base.jar}} with the added constructor, the compilation works fine:{{{{}} javac --patch-module java.base=java_base.jar src\main\java\poc\Main.java{}}}.
 * Attempting to do the same using Maven compiler plugin results in NullPointerException: {{mvn -X compile}}

h2. Walkaround

I was able to fix the problem by adding the line
{code:java}
pathElements = Collections.emptyMap(); {code}
to the else part of the {{{}CompilerMojo.preparePaths{}}}.

The compilation started working, it does however produce a warning
{noformat}
[WARNING] Can't locate java_base.jar{noformat}
every single time. I did not investigate much the cause of this message.

Also note that while similar, this issues is not the same as MCOMPILER-311.

  was:
h2. Summary

When using {{--patch-module}} compiler argument, there is a {{NullPointerException}} due to field {{pathElements}} not being initialized in {{{}CompilerMojo{}}}.
h2. Description

The method {{preparePaths}} in {{CompilerMojo}} has two code paths:
{code:java}
@Override
protected void preparePaths( Set<File> sourceFiles )
{
    boolean hasModuleDescriptor = false;
    // ...
    if ( hasModuleDescriptor )
    {
        modulepathElements = new ArrayList<>( compilePath.size() );
        classpathElements = new ArrayList<>( compilePath.size() );
        pathElements = new LinkedHashMap<>( compilePath.size() );
    }
    else
    {
        classpathElements = new ArrayList<>();
        modulepathElements = Collections.emptyList();
        // ...
    }
}{code}
Notice that in the else part, {{pathElements}} is not initialized. This field is used when the compiler arguments contain {{--patch-module}} switch. So whenever the compiler is used with this switch and there is no module descriptor in the project, NPE occurs.
h2. Proof-of-concept

Attached is a simple proof-of-concept to illustrate the issue. The project consists of a single class with raises {{NullPointerException}} using a new constructor {{{}NullPointerException(Throwable){}}}, which does not exist in base JDK.
 * When executing {{javac}}{{{} src\main\java\poc\Main.java{}}}, the compilation fails as expected.
 * Using a replacement {{NullPointerException}} class in {{java_base.jar}} with the added constructor, the compilation works fine:{{{} javac --patch-module java.base=test.jar src\main\java\poc\Main.java{}}}.
 * Attempting to do the same using Maven compiler plugin results in NullPointerException: {{mvn -X compile}}

h2. Walkaround

I was able to fix the problem by adding the line
{code:java}
pathElements = Collections.emptyMap(); {code}
to the else part of the {{{}CompilerMojo.preparePaths{}}}.

The compilation started working, it does however produce a warning
{noformat}
[WARNING] Can't locate java_base.jar{noformat}
every single time. I did not investigate much the cause of this message.

Also note that while similar, this issues is not the same as MCOMPILER-311.


> NullPointerException when using --patch-module compiler argument
> ----------------------------------------------------------------
>
>                 Key: MCOMPILER-510
>                 URL: https://issues.apache.org/jira/browse/MCOMPILER-510
>             Project: Maven Compiler Plugin
>          Issue Type: Bug
>    Affects Versions: 3.10.1
>            Reporter: Artem K.
>            Priority: Major
>         Attachments: poc.zip
>
>
> h2. Summary
> When using {{--patch-module}} compiler argument, there is a {{NullPointerException}} due to field {{pathElements}} not being initialized in {{{}CompilerMojo{}}}.
> h2. Description
> The method {{preparePaths}} in {{CompilerMojo}} has two code paths:
> {code:java}
> @Override
> protected void preparePaths( Set<File> sourceFiles )
> {
>     boolean hasModuleDescriptor = false;
>     // ...
>     if ( hasModuleDescriptor )
>     {
>         modulepathElements = new ArrayList<>( compilePath.size() );
>         classpathElements = new ArrayList<>( compilePath.size() );
>         pathElements = new LinkedHashMap<>( compilePath.size() );
>     }
>     else
>     {
>         classpathElements = new ArrayList<>();
>         modulepathElements = Collections.emptyList();
>         // ...
>     }
> }{code}
> Notice that in the else part, {{pathElements}} is not initialized. This field is used when the compiler arguments contain {{--patch-module}} switch. So whenever the compiler is used with this switch and there is no module descriptor in the project, NPE occurs.
> h2. Proof-of-concept
> Attached is a simple proof-of-concept to illustrate the issue. The project consists of a single class with raises {{NullPointerException}} using a new constructor {{{}NullPointerException(Throwable){}}}, which does not exist in base JDK.
>  * When executing {{{}javac{}}}{{{{}} src\main\java\poc\Main.java{}}}, the compilation fails as expected.
>  * Using a replacement {{NullPointerException}} class in {{java_base.jar}} with the added constructor, the compilation works fine:{{{{}} javac --patch-module java.base=java_base.jar src\main\java\poc\Main.java{}}}.
>  * Attempting to do the same using Maven compiler plugin results in NullPointerException: {{mvn -X compile}}
> h2. Walkaround
> I was able to fix the problem by adding the line
> {code:java}
> pathElements = Collections.emptyMap(); {code}
> to the else part of the {{{}CompilerMojo.preparePaths{}}}.
> The compilation started working, it does however produce a warning
> {noformat}
> [WARNING] Can't locate java_base.jar{noformat}
> every single time. I did not investigate much the cause of this message.
> Also note that while similar, this issues is not the same as MCOMPILER-311.



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