Empty <argument> tag adds null to args

[Anders-E]

I'm not sure if this is intended but any empty <argument> tag adds null to String[] args.

I noticed this since it caused a NullPointerException when trying to parse arguments with Apache CLI. Stacktrace:

java.lang.NullPointerException
    at org.apache.commons.cli.DefaultParser.handleToken (DefaultParser.java:237)
    at org.apache.commons.cli.DefaultParser.parse (DefaultParser.java:120)
    at org.apache.commons.cli.DefaultParser.parse (DefaultParser.java:76)
    at org.apache.commons.cli.DefaultParser.parse (DefaultParser.java:60)
    [...]
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke (Method.java:566)
    at org.codehaus.mojo.exec.ExecJavaMojo$1.run (ExecJavaMojo.java:282)
    at java.lang.Thread.run (Thread.java:834)

The reason for me occasionally using an empty <argument> tag is that I'm using a little workaround for combining CLI-arguments with arguments specified within pom.xml as such:

<properties>
    <!-- My additional args from CLI -->
    <doc.args/>
</properties>
<build>
    <plugins>
        <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>exec-maven-plugin</artifactId>
            <version>1.6.0</version>
            <executions>
                <execution>
                    <goals>
                        <goal>exec</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <mainClass>com.my.main.Class</mainClass>
                <arguments>
                    <!-- My default args -->
                    <argument>-a</argument>
                    <argument>myDefaultArgA</argument>
                    <argument>-b</argument>
                    <argument>myDefaultArgB</argument>

                    <!-- Append my CLI args -->
                    <argument>${doc.args}</argument>
                </arguments>
            </configuration>
        </plugin>
    </plugins>
</build>

As of now, I have to keep a placeholder to avoid the crash:

<properties>
    <doc.args>placeholder</doc.args>
</properties>

Which I don't like since the placeholder still gets passed on to the program. Shouldn't an empty <argument> tag not add anything to String[] args at all?

[ctubbsii]

An empty argument tag should add an empty string. See my comment on #133 (comment)