Groovy Eclipse compiler plugin for maven not compiling anything - eclipse

Question

I'm trying to understand the correct setup of a Java and Groovy project in Maven, compiling the source files with groovy-eclipse-compiler.
According to the plugin site, if you have files in src/main/java and src/test/java the compiler should find both Java and Groovy by default.
Setting up the build like the example makes target/classes empty.
<build>
...
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.3.2</version>
<configuration>
<compilerId>groovy-eclipse-compiler</compilerId>
<!-- set verbose to be true if you want lots of uninteresting messages -->
<!-- <verbose>true</verbose> -->
</configuration>
<dependencies>
<dependency>
<groupId>org.codehaus.groovy</groupId>
<artifactId>groovy-eclipse-compiler</artifactId>
<version>2.7.0-01</version>
</dependency>
</dependencies>
</plugin>
...
</plugins>
</build>
The only way I found to make it work was to use the build-helper-maven-plugin. This is the option used by the Archetype too:
mvn archetype:generate \
-DarchetypeGroupId=org.codehaus.groovy \
-DarchetypeArtifactId=groovy-eclipse-quickstart \
-DarchetypeVersion=2.5.2-SNAPSHOT \
-DgroupId=foo \
-DartifactId=bar \
-Dversion=1 \
-DinteractiveMode=false \
-DarchetypeRepository=https://nexus.codehaus.org/content/repositories/snapshots/
So, it's the page outdated? Isn't enough have Java files in the src folder?

Answer 1

I'm able to get this to work. Here is what I did:
create the archetype as you did above.
edit the pom.xml to the file below
mv everything from src/main/groovy to src/main/java and the same for the tests.
remove the empty groovy dirs
rename all *.java files to *.groovy
mvn clean compile
I get some expected compile errors due to differences in Java vs groovy syntax, but all groovy files are recognized.
Does this work for you? If not what is different?
Here is the pom file I am using:
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>foo</groupId>
<artifactId>bar</artifactId>
<version>1</version>
<name>bar Groovy Eclipse Maven Java App</name>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.3.2</version>
<configuration>
<compilerId>groovy-eclipse-compiler</compilerId>
</configuration>
<dependencies>
<dependency>
<groupId>org.codehaus.groovy</groupId>
<artifactId>groovy-eclipse-compiler</artifactId>
<version>2.7.0-01</version>
<exclusions>
<exclusion>
<groupId>org.codehaus.groovy</groupId>
<artifactId>groovy-eclipse-batch</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.codehaus.groovy</groupId>
<artifactId>groovy-eclipse-batch</artifactId>
<version>2.1.1-01</version>
</dependency>
</dependencies>
</plugin>
</plugins>
</build>
<dependencies>
<dependency>
<groupId>org.codehaus.groovy</groupId>
<artifactId>groovy-all</artifactId>
<version>2.1.1</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.8.2</version>
<scope>test</scope>
</dependency>
</dependencies>
</project>
EDIT
Since I misunderstood the actual question, and you do want to keep the files separate, then there are 2 options:
using the build-helper-plugin as you have done
Use the groovy-eclipse-compiler mojo:
<plugin>
<groupId>org.codehaus.groovy</groupId>
<artifactId>groovy-eclipse-compiler</artifactId>
<version>2.7.0-01</version>
<extensions>true</extensions>
</plugin>
</build>
This is all described on the groovy-eclipse-compiler page.