2.15+ - Services dependent on libraries without classes no longer build

[mikethecalamity]

Describe the bug

When trying to upgrade to Quarkus 2.15 or higher (tested with 2.15.0.Final, 2.15.3.Final, 2.16.0.CR1), libraries that don't contain classes that are included as a dependency in a Quarkus project no longer can be built because The project does not contain a class output directory. .../build/classes must exist..

In the example provided in the reproducer, the library lib2 contains src/main/resources but no Java classes (i.e. src/main/java). The Quarkus service service4 pulls in lib2 as a dependency. The build for service4 fails because lib2 does not have build/classes.

Expected behavior

Successful build

Actual behavior

org.gradle.api.GradleException: The project does not contain a class output directory. quarkus-test\common\subprojects\lib2\build\classes must exist.
        at io.quarkus.gradle.tooling.GradleApplicationModelBuilder.addSubstitutedProject(GradleApplicationModelBuilder.java:552)
        at io.quarkus.gradle.tooling.GradleApplicationModelBuilder.collectDependencies(GradleApplicationModelBuilder.java:305)
        at io.quarkus.gradle.tooling.GradleApplicationModelBuilder.lambda$collectDependencies$0(GradleApplicationModelBuilder.java:218)
        at io.quarkus.gradle.tooling.GradleApplicationModelBuilder.collectDependencies(GradleApplicationModelBuilder.java:217)
        at io.quarkus.gradle.tooling.GradleApplicationModelBuilder.buildAll(GradleApplicationModelBuilder.java:117)
        at io.quarkus.gradle.tooling.ToolingUtils.create(ToolingUtils.java:74)
        at io.quarkus.gradle.tooling.ToolingUtils.create(ToolingUtils.java:70)
        at io.quarkus.gradle.extension.QuarkusPluginExtension.getApplicationModel(QuarkusPluginExtension.java:135)
        at io.quarkus.gradle.tasks.QuarkusGenerateCode.prepareQuarkus(QuarkusGenerateCode.java:95)

How to Reproduce?

Reproducer:

1. Clone https://github.com/mikethecalamity/quarkus-test
2. ./gradlew -p apps service4:build

Note that the project lib2 only contains src/main/resources so it should not have build/classes.

Output of uname -a or ver

No response

Output of java -version

17.0.5

GraalVM version (if different from Java)

No response

Quarkus version or git rev

2.15.3.Final / 2.16.0.CR1

Build tool (ie. output of mvnw --version or gradlew --version)

Gradle 7.5.1

Additional information

No response