[MCOMPILER-533] Output an error when --release option is used together with --source or --target

[sos-jira-migration-bot]

Arend von Reinersdorff opened MCOMPILER-533 and commented

javac outputs an error when the --release option is used together with the --source or --target option. See https://docs.oracle.com/en/java/javase/17/docs/specs/man/javac.html#option-release

For example:
javac --release 17 --target 17 ...
Will fail with this error:
error: option --target cannot be used together with --release

This is nice because it informs the user of misconfiguration and enforces the use of only --release or only --source/--target.

Unfortunately, the error is lost when compiling with Maven. Maven uses the release option and silently ignores source and target. Users don't notice when they unnecessarily set both. See for example spring-projects/spring-boot#34761

For example:
<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.11.0</version>
    <configuration>
        <release>17</release>
        <source>17</source>
        <target>17</target>
    </configuration>
</plugin>
Compiles using the release option without any error or warning.

It would be nice to restore the error from javac in Maven, or output a similar one.
The problem I see is that Maven uses default values for source and target. When the user sets only the release option, no error or warning should be caused because of the default values for source and target.

---

Affects: 3.11.0

Issue Links:

• MCOMPILER-582 Automatic detection of release option for JDK < 9

[sos-jira-migration-bot]

Jorge Solórzano commented

There are some scenarios where it might be useful to have this behavior, some projects set source/target to compile to Java 8 and use a profile to compile to Java 9 using the -release option.

The error is not lost because Maven gives priority to the -release option, and that should be correct, it does not set the source/target so no error occurs.

Yet, I think that a warning should be displayed mentioning that --target is ignored when used together with --release if both are set.

[sos-jira-migration-bot]

Slawomir Jaranowski commented

Many projects use as default source/target and in profile with JDK 9+ add also release.

When we generate warning we will force user to preparing more complicated configurations with more profiles.

Even more we next version of compiler we will can provided all parameter without profiles.