maven-shade-plugin reports: Error creating shaded jar: ...target/classes (Is a directory)
<p>When running a Maven build in eclipse using the m2eclipse tooling for a project that is configured for the <a href="https://maven.apache.org/plugins/maven-shade-plugin/" rel="noreferrer">Maven Shade Plugin</a>, the build fails with the following error message:</p>

<p><code>Failed to execute goal org.apache.maven.plugins:maven-shade-plugin:2.4.3:shade (default) on project xxx: Error creating shaded jar: /.../project/target/classes (Is a directory) -&gt; [Help 1]
</code></p>

<p>I tried different versions of the Shade plugin and tried with different Java versions (6,7,8). All lead to the same error.</p>

<p><strong>Workaround:</strong></p>

<p>The solution for <a href="https://stackoverflow.com/a/31330682/270662">this question</a> provides a workaround: The error only occurs if the option <code>Resolve Workspace Artifacts</code> is selected. If this option is not selected, the build runs fine.</p>

<p>(However, this does not solve the problem since it is often very useful to build projects with enabled workspace resolution).</p>