我的scala-maven-plugin与多模块项目的配置不允许我在子目录中执行'mvn compile'

Question

We are using the scala-maven-plugin for our mixed Java/Scala project. Works nicely in general, but we have found that with a multi-module project we can't figure out how to do a'mvn compile' in a subdirectory.

I am unable to post my full source code to IP restrictions, but in my search for other projects that might have solved this issue I only managed to come up with other projects with the exact same problem. Here is one for example: https://github.com/buildlackey/scala-multimodule-sample-project.git

The above project has three submodules beneath the directory that holds the root pom.xml: cats , dogs and web-application . If you git clone the above url, then cd to 'scala-multimodule-sample-project', you will see it build. Now if I cd into the sub-module 'dogs' and do a 'mvn compile', I see the message:

[INFO] No sources to compile

But there are sources to compile ! The plugin is just not finding them.

This is the same thing that happens on my multi-module project. I can't post the whole source for our stuff.. But here is the relevant configuration from our top level pom.xml :

<build>
    <sourceDirectory>${basedir}/src/main/scala</sourceDirectory>
    <testSourceDirectory>${basedir}/src/test/scala</testSourceDirectory>

  <!-- Compiling scala code -->
        <plugin>
          <!-- see http://davidb.github.com/scala-maven-plugin -->
          <groupId>net.alchim31.maven</groupId>
      <artifactId>scala-maven-plugin</artifactId>
      <version>3.2.2</version>
      <executions>
        <execution>
          <id>scala-compile</id>
          <phase>process-resources</phase>
          <goals>
            <goal>add-source</goal>
            <goal>compile</goal>
          </goals>
        </execution>
        <execution>
          <id>scala-test-compile</id>
          <phase>process-test-resources</phase>
          <goals>
            <goal>testCompile</goal>
          </goals>
        </execution>
      </executions>
    </plugin>

According to the documentation for the plug-in ( http://davidb.github.io/scala-maven-plugin/add-source-mojo.html ) there are are optional parameters that can be passed to the add-source goal: namely, sourceDir and testSourceDir

However, I could not figure out how to pass these. Maybe those parameters are the key to success here ?

Finally, one kind of silly work-around that proved successful is to copy the same configuration for scala-maven-plugin into each submodule directory where I want to do a compile restricted to that submodule. Obviously this is a non-DRY, undesirable approach.

I'd be most grateful if anyone could suggest a good solution.

Thanks !

Answer 1

I uploaded a working sample at https://github.com/davidB/scala-maven-plugin/tree/master/samples/prj_multi_modules

The duplicate solution is the common usage.

The DRY alternative is to declare the configuration of the plugin in the <pluginManagement> section, then add under <build><plugins><plugin> the groupId + artifactId for project(s) where you want to enable the plugin. You can add it into modules'pom.xml or into parent's pom.xml inherited by every modules. You could also use <dependencyManagement> to avoid duplicate dependency's version.

The addSource is to register additional source directory and expose it for IDE and other plugins.

Answer 2

I think you have wrong value for sourceDir in your scala-multimodule-sample-project pom.xml file.

I change sourceDir to the src/main/scala and after mvn compile I have the following output:

...
[INFO] skip non existing resourceDirectory /home/grzesiek/dev/project/temp/scala-multimodule-sample-project/cats/src/main/resources
[INFO] 
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ cats ---
[INFO] No sources to compile
[INFO] 
[INFO] --- maven-scala-plugin:2.15.2:compile (default) @ cats ---
[INFO] Checking for multiple versions of scala
[INFO] includes = [**/*.java,**/*.scala,]
[INFO] excludes = []
[INFO] /home/grzesiek/dev/project/temp/scala-multimodule-sample-project/cats/src/main/scala:-1: info: compiling
[INFO] Compiling 1 source files to /home/grzesiek/dev/project/temp/scala-multimodule-sample-project/cats/target/classes at 1453711735781
...