How do I change warnings to Errors with Error Prone?

When I run mvn clean compile

   <plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <configuration>
      <compilerId>javac-with-errorprone</compilerId>
      <forceJavacCompilerUse>true</forceJavacCompilerUse>
      <showDeprecation>true</showDeprecation>
      <showWarnings>true</showWarnings>
    </configuration>
    <dependencies>
      <dependency>
        <groupId>org.codehaus.plexus</groupId>
        <artifactId>plexus-compiler-javac-errorprone</artifactId>
        <version>2.6</version>
      </dependency>
      <dependency>
        <groupId>com.google.errorprone</groupId>
        <artifactId>error_prone_core</artifactId>
        <version>2.0.6</version>
      </dependency>
    </dependencies>
  </plugin>

I've been trying to get MissingOverride enabled as an error, or really just to emit anything, for starters what do I need to change to see output from "warnings" then what should I do to get MissingOverride to be an error?

Solution

It seems like a bug with plexus-compiler-javac-errorprone that it doesn't output warnings, but to convert MissingOverride to an error, you can pass a -Xep:MissingOverride:ERROR flag to the compiler, as follows:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.3</version>
    <configuration>
        <compilerId>javac-with-errorprone</compilerId>
        <forceJavacCompilerUse>true</forceJavacCompilerUse>
        <source>1.8</source>
        <target>1.8</target>
        <compilerArgs>
            <arg>-Xep:MissingOverride:ERROR</arg>
        </compilerArgs>
    </configuration>
    <dependencies>
        <dependency>
            <groupId>org.codehaus.plexus</groupId>
            <artifactId>plexus-compiler-javac-errorprone</artifactId>
            <version>2.6</version>
        </dependency>
        <dependency>
            <groupId>com.google.errorprone</groupId>
            <artifactId>error_prone_core</artifactId>
            <version>2.0.7</version>
        </dependency>
    </dependencies>
</plugin>