When using the scala-maven-plugin, you might need to exclude specific Scala files from compilation. For example, if you have two Scala files—Spark_1.6.1.scala and Spark_2.0.1.scala—in src/main/scala/test and want to exclude the first one, you need to configure the excludes properly.

A common mistake is assuming the exclude pattern supports full path matching. However, scala-maven-plugin only applies patterns to paths inside /test/scala/ or /main/scala/. Therefore, you must use package-style patterns relative to these base directories.

Below is a correct configuration example that excludes all files under the package com.excludes_package and its subpackages:

<excludes>
    <exclude>**/com/excludes_package/**</exclude>
    <exclude>**/com/excludes_package/excludes_package_1/**</exclude>
    <exclude>**/com/excludes_package/excludes_package_2/**</exclude>
</excludes>

Important considerations:

• Pattern scope: Patterns like /test/ are invalid. Always base patterns on the path starting from src/main/scala/ or src/test/scala/.
• Incremental mode: Contrary to some earlier reports, incremental compilation (via <recompileMode>incremental</recompileMode>) does support excludes. You can safely enable it.
• Java compilation: To prevent errors during the Java build phase, you should also add the same excludes to the maven-compiler-plugin configuration. This ensures that excluded Scala files are not inadvertently compiled by the Java compiler.

Here is a complete, working configuration for a mixed Java/Scala project:

<!-- Scala plugin -->
<plugin>
    <groupId>net.alchim31.maven</groupId>
    <artifactId>scala-maven-plugin</artifactId>
    <version>3.2.2</version>
    <executions>
        <execution>
            <id>eclipse-add-source</id>
            <goals>
                <goal>add-source</goal>
            </goals>
        </execution>
        <execution>
            <id>scala-compile-first</id>
            <phase>process-resources</phase>
            <goals>
                <goal>compile</goal>
            </goals>
        </execution>
        <execution>
            <id>scala-test-compile-first</id>
            <phase>process-test-resources</phase>
            <goals>
                <goal>testCompile</goal>
            </goals>
        </execution>
        <execution>
            <id>attach-scaladocs</id>
            <phase>verify</phase>
            <goals>
                <goal>doc-jar</goal>
            </goals>
        </execution>
    </executions>
    <configuration>
        <scalaVersion>${scala.version}</scalaVersion>
        <recompileMode>incremental</recompileMode>
        <useZincServer>true</useZincServer>
        <args>
            <arg>-unchecked</arg>
            <arg>-deprecation</arg>
            <arg>-feature</arg>
            <arg>-language:postfixOps</arg>
        </args>
        <jvmArgs>
            <jvmArg>-Xms1024m</jvmArg>
            <jvmArg>-Xmx1024m</jvmArg>
            <jvmArg>-XX:ReservedCodeCacheSize=${CodeCacheSize}</jvmArg>
        </jvmArgs>
        <javacArgs>
            <javacArg>-source</javacArg>
            <javacArg>${java.version}</javacArg>
            <javacArg>-target</javacArg>
            <javacArg>${java.version}</javacArg>
            <javacArg>-Xlint:all,-serial,-path</javacArg>
        </javacArgs>
        <excludes>
            <exclude>**/com/excludes_package/**</exclude>
            <exclude>**/com/excludes_package/excludes_package_1/**</exclude>
            <exclude>**/com/excludes_package/excludes_package_2/**</exclude>
        </excludes>
    </configuration>
</plugin>

<!-- Java compiler plugin with matching excludes -->
<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.6.1</version>
    <configuration>
        <source>${java.version}</source>
        <target>${java.version}</target>
        <encoding>UTF-8</encoding>
        <maxmem>1024m</maxmem>
        <fork>true</fork>
        <compilerArgs>
            <arg>-Xlint:all,-serial,-path</arg>
        </compilerArgs>
        <excludes>
            <exclude>**/com/excludes_package/**</exclude>
            <exclude>**/com/excludes_package/excludes_package_1/**</exclude>
            <exclude>**/com/excludes_package/excludes_package_2/**</exclude>
        </excludes>
    </configuration>
    <executions>
        <execution>
            <phase>compile</phase>
            <goals>
                <goal>compile</goal>
            </goals>
        </execution>
    </executions>
</plugin>

With this setup, the **/com/excludes_package/** patterns will correctly exclude all matching files from both Scala and Java compilation. Remember that the exclude path is relative to the source root (e.g., src/main/scala), not the full filesystem path.