Passing scalac opts to Maven from the command-line or environment

Question

I'm looking for an unobtrusive way to make mvn aware of additional flags I'd like to pass to the scalac compiler via the command-line or environment variables only.

I'm currently using the scala-maven-plugin with a command such as:

mvn --show-version --batch-mode --errors compile

In this case I want mvn to treat the compile stage as if it had been passed flags such as:

scalac -encoding utf8 -deprecation -unchecked -Xlint:_ -Werror -Wdead-code -Wunused:_

I do not want to touch the project's pom.xml. The reason for that in this case is that this is a step in an upstream CI/CD templates repository, so I don't have permission to mess with the Maven configuration of the downstream projects.

It does not appear that this is what MAVEN_OPTS is made for, so I'm wondering if there is some alternative to talk to scalac.

Answer 1

Using scala:compile with -DaddScalacArgs allows you to pass additional flags to scalac:

Example:

mvn \
  --show-version \
  --batch-mode \
  --errors \
  scala:compile \
  -DaddScalacArgs='-unchecked|-deprecation|-explaintypes|-Xfatal-warnings|-Xlint:_'

Documentation:

• https://davidb.github.io/scala-maven-plugin/compile-mojo.html#addScalacArgs
• https://davidb.github.io/scala-maven-plugin/example_compile.html

Note that the available options to scalac have changed with Scala versions.

You can use:

• mvn scala:help
• scalac -X
• scalac -Xlint:help

To see the underlying version and the available -X options.