ECJ batch compiler does not load multi-release module declaration when -target is used

[Marcono1234]

Version

ecj-3.38.0.jar from Maven Central

Description

When using the ECJ batch compiler and using -target respectively one of the shorthand variants such as -9 it does not load the module descriptor of a multi-release JAR (which contains the module descriptor for example as META-INF/versions/9/module-info.class).

It only loads the module descriptor when --release instead of -target is used. And due to https://bugs.eclipse.org/bugs/show_bug.cgi?id=577790 / #2778 the version for --release must match exactly, but that is tracked in that issue.

This differs from javac which seems to load the module descriptor when for example -target 9 is used.

(This might affect not only the module descriptor but any class under the versions directory, but not sure if that matters since the JAR specification says those classes must have the same API as the classes in the top-level directory.)

Reproduction steps

1. Download the attached multi-release-test.zip and unzip it
2. Download ECJ, for example from https://search.maven.org/artifact/org.eclipse.jdt/ecj
3. Run ECJ with -target 10 (or alternatively -10)

   java -jar ./ecj.jar -source 10 -target 10 --module-path ./multi-release.jar ./module-info.java
   

   ❌ Bug: It cannot find the referenced module
4. Run ECJ with --release 10

   java -jar ./ecj.jar --release 10 --module-path ./multi-release.jar ./module-info.java
   

   ℹ️ As expected: Compilation succeeds

Now compare with javac behavior:

1. Run with -target 10

   javac -source 9 -target 10 --module-path ./multi-release.jar ./module-info.java
   

   ℹ️ As expected: Compilation succeeds
2. Run with javac -target 9

   javac -source 9 -target 10 --module-path ./multi-release.jar ./module-info.java
   

   ℹ️ As expected: Compilation fails because it cannot find the referenced module (because it is under META-INF/versions/10)
   This proves that the -target option seems to determine which versions directories are checked in the JAR

(Tested with JDK 17)

[iloveeclipse]

Would you please provide all the data in one project / zip file so that one could have an easy to use reproducer without extra tedious manual steps?

[Marcono1234]

Sorry, have added a single ZIP file now and updated the steps above.