https://issues.apache.org/jira/browse/MCOMPILER-174
                    (Compare what guava-gwt has to do for maven-javadoc-plugin.)
                -->
                <arg>-sourcepath</arg>
                <arg>doesnotexist</arg>
              </compilerArgs>
            </configuration>
          </execution>
          <execution>
            <id>compile-java9</id>
            <goals>

        builder.setProperty("project.buildpath", validClasspath.asPath)
        builder.setClasspath(validClasspath.files.toTypedArray())

        val validSourcepath = sourcepath.filter { it.exists() }
        builder.setProperty("project.sourcepath", validSourcepath.asPath)
        builder.setSourcepath(validSourcepath.files.toTypedArray())

        val builtJar = builder.build()
        if (!builder.isOk) {

          </sourceFileExcludes>
          <!-- The above exclusion doesn't actually matter unless I prevent Javadoc from autodiscovering the source in the sourcepath, which defaults to the source directory :\ Boo for -sourcepath. -->
          <sourcepath>doesnotexist</sourcepath>

                the base compiler settings (in the root `pom.xml`) to enable MRJAR output.
              -->
              <compilerArgs combine.self="override">
                <arg>-sourcepath</arg>
                <arg>${project.basedir}/src</arg>
                <arg>--add-reads=com.google.common=ALL-UNNAMED</arg>
                <arg>--add-reads=com.google.common.testlib=ALL-UNNAMED</arg>

                the base compiler settings (in the root `pom.xml`) to enable MRJAR output.
              -->
              <compilerArgs combine.self="override">
                <arg>-sourcepath</arg>
                <arg>${project.basedir}/src</arg>
                <arg>--add-reads=com.google.common=ALL-UNNAMED</arg>
                <arg>--add-reads=com.google.common.testlib=ALL-UNNAMED</arg>

                base compile settings (in the root `pom.xml`) to enable MRJAR output.
              -->
              <compilerArgs combine.self="override">
                <arg>-sourcepath</arg>
                <arg>${project.basedir}/src</arg>
                <arg>--add-reads=com.google.common=ALL-UNNAMED</arg>
                <!-- https://errorprone.info/docs/installation#maven -->

                base compile settings (in the root `pom.xml`) to enable MRJAR output.
              -->
              <compilerArgs combine.self="override">
                <arg>-sourcepath</arg>
                <arg>${project.basedir}/src</arg>
                <arg>--add-reads=com.google.common=ALL-UNNAMED</arg>
                <!-- https://errorprone.info/docs/installation#maven -->

                      https://issues.apache.org/jira/browse/MCOMPILER-174
                      (Compare what guava-gwt has to do for maven-javadoc-plugin.)
                  -->
                  <arg>-sourcepath</arg>
                  <arg>doesnotexist</arg>
                </compilerArgs>
              </configuration>
            </execution>
            <execution>
              <id>default-testCompile</id>

        });
        sourcesPath.setCanBeConsumed(false);
        sourcesPath.setCanBeResolved(true);
        sourcesPath.extendsFrom(runtimeClasspath);

        extension.getClasspath().from(runtimeClasspath);
        extension.getSourceRoots().from(sourcesPath.getIncoming().artifactView(v -> v.lenient(true)).getFiles());

            super(key);
        }
    }

    @Override
    protected ObjectiveProperties newObjectiveProperties(final String resourcePath, final PropertyFilter propertyFilter) {
        return new ObjectiveProperties(resourcePath) { // for e.g. checking existence and filtering value
            Cache<String, String> cache = CacheBuilder.newBuilder().build();

            @Override