[FIXED] Exception While Using net.alchim31.maven:scala-maven-plugin

Issue

I have a scala-maven-spark project. Here is my pom.xml file

<properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <scala.version>2.11.8</scala.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.scalatest</groupId>
            <artifactId>scalatest_2.11</artifactId>
            <version>3.0.2</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-sql_2.11</artifactId>
            <version>2.4.0</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>
            <version>28.1-jre</version>
        </dependency>
        
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-api-scala_2.11</artifactId>
            <version>11.0</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-core</artifactId>
            <version>2.17.0</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-api</artifactId>
            <version>2.17.0</version>
        </dependency>

    </dependencies>
    <build>
        <sourceDirectory>src/main/scala</sourceDirectory>
        <testSourceDirectory>src/test/scala</testSourceDirectory>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>2.7</version>
                <configuration>
                    <skipTests>true</skipTests>
                </configuration>
            </plugin>
            <plugin>
                <groupId>net.alchim31.maven</groupId>
                <artifactId>scala-maven-plugin</artifactId>
                <version>3.3.3</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>compile</goal>
                            <goal>testCompile</goal>
                        </goals>
                    </execution>
                </executions>
              <configuration>
                  <scalaVersion>${scala.version}</scalaVersion>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.scalatest</groupId>
                <artifactId>scalatest-maven-plugin</artifactId>
                <version>1.0</version>
                <configuration>
                    <reportsDirectory>${project.build.directory}/surefire-reports</reportsDirectory>
                    <junitxml>.</junitxml>
                    <filereports>WDF TestSuite.txt</filereports>
                </configuration>
                <executions>
                    <execution>
                        <id>test</id>
                        <goals>
                            <goal>test</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-shade-plugin</artifactId>
                <version>3.2.1</version>
                <executions>
                    <!-- Run shade goal on package phase -->
                    <execution>
                        <phase>package</phase>
                        <goals>
                            <goal>shade</goal>
                        </goals>
                        <configuration>
                            <createDependencyReducedPom>false</createDependencyReducedPom>
                            <filters>
                                <filter>
                                    <artifact>*:*</artifact>
                                    <excludes>
                                        <exclude>META-INF/*.SF</exclude>
                                        <exclude>META-INF/*.DSA</exclude>
                                        <exclude>META-INF/*.RSA</exclude>
                                    </excludes>
                                </filter>
                            </filters>
                            <finalName>${project.artifactId}-${project.version}</finalName>
                            <relocations>
                                <relocation>
                                    <pattern>com.google.protobuf</pattern>
                                    <shadedPattern>shaded.com.google.protobuf</shadedPattern>
                                </relocation>
                                <relocation>
                                    <pattern>com.google.common</pattern>
                                    <shadedPattern>shaded.com.google.common</shadedPattern>
                                </relocation>
                            </relocations>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

When I run mvn clean package I am getting the below error

[ERROR] Failed to execute goal net.alchim31.maven:scala-maven-plugin:3.3.3:compile (default) on project decisionengine-data-ingestion-maven: wrap: org.apache.commons.exec.ExecuteException: Process exited with an error: 1 (Exit value: 1)

If I remove the net.alchim31.maven plugin the build completes successfully.

Error details

[ERROR] error: scala.reflect.internal.MissingRequirementError: object java.lang.Object in compiler mirror not found.
[ERROR]         at scala.reflect.internal.MissingRequirementError$.signal(MissingRequirementError.scala:17)
[ERROR]         at scala.reflect.internal.MissingRequirementError$.notFound(MissingRequirementError.scala:18)
[ERROR]         at scala.reflect.internal.Mirrors$RootsBase.getModuleOrClass(Mirrors.scala:53)
[E

Solution

If you have scala source code you need

• to add the scala-maven-plugin (please use a more recent version see https://search.maven.org/search?q=a:scala-maven-plugin, today 4.5.6 is the latest, why using 3.3.3 from 2018-06 ?) to compile your code
• to have the scala-library as an explicit dependency

And remove

              <configuration>
                  <scalaVersion>${scala.version}</scalaVersion>
                </configuration>

It's better to let the plugin detects the scala version from dependencies.

Answered By - David Bernard
Answer Checked By - Candace Johnson (JavaFixing Volunteer)