'jvm-1.8' is not a valid choice for '-target'

Question

IntelliJ complains with the following exception when I try to make my project.

Error:scalac: \'jvm-1.8\' is not a valid choice for \'-target\'
Error:scalac:          


        

Answer 1

If you're using JDK 1.8 as your IntelliJ Project SDK, then the default project language level and source compatibility may be set to version 8 by default. This will also be reflected in IntelliJ's Scala compiler settings.

To override default Java 8 language level, it was only necessary for me to add the following to my build.gradle:

sourceCompatibility = 1.7

After doing that, make IntelliJ IDEA import the Gradle project again. You should then confirm that the change has been picked up by IntelliJ by checking under: Settings -> Build, Execution, Deployment -> Compiler -> Scala Compiler

Look at the Additional compiler options field for each of the modules listed and make sure that it contains -target:jvm-1.7, and not -target:jvm-1.8.

Under Project Settings -> Modules, you should see that the Language Level is now set to 7 too.

N.B. Setting the sourceCompatibility property under the Gradle properties allprojects, subprojects or using tasks.withType(ScalaCompile) did not work for me; it had to be specified separately to be picked up.

(This worked for me using IntelliJ IDEA 2017.2.3, Gradle 4.1, the Gradle Scala plugin and Scala version 2.10)