Documentation doesn't render properly if a module is empty

[xenoterracide]

Given

public class ModulithTest {
  private final Logger log = LogManager.getLogger(this.getClass());

  // this is not a test but rather a silly way to manually run documentation generation
  @Test
  void writeDocumentationSnippets() {
    // hacky hack because the test is not run by the Spring Boot Test Runner
    System.setProperty("spring.modulith.detection-strategy", "explicitly-annotated");
    var modules = ApplicationModules.of(Application.class);

    modules.forEach(module -> log.info("Module: {}", module));

    new Documenter(modules).writeDocumentation();
  }
}

When

@Module("Annotations")
@InfrastructureLayer
@NullMarked
package com.myorg.annotation;

import org.jmolecules.architecture.layered.InfrastructureLayer;
import org.jmolecules.ddd.annotation.Module;
import org.jspecify.annotations.NullMarked;

@NullMarked
@Module("Utilities")
@InfrastructureLayer
package com.myorg.tool;

import org.jmolecules.architecture.layered.InfrastructureLayer;
import org.jmolecules.ddd.annotation.Module;
import org.jspecify.annotations.NullMarked;

package com.myorg.annotation;

class A {
}

and there are no class in com.myorg.tool outside of the package-info.java

Then

the component diagram is incorrectly generated without any components

@startuml
set separator none
title Application

top to bottom direction

!include <C4/C4>
!include <C4/C4_Context>


SHOW_LEGEND(true)
@enduml

removing com.myorg.tool or adding a class that depends on the annotation package will generate the diagram correctly.

Version

modulith 1.4.3 java 21

[odrotbohm]

Good catch, thanks! What would you like to see in this case? No file generated at all?

[xenoterracide]

To me the module is still there with no dependencies. In the components diagram I would still just show two modules. Alternatives might be an error telling you what's up that way you could easily debug it. It could also be argued that you should only show the module with classes. I don't think silently skipping the diagram is the right idea since there is still one module that's actually present.

Ps this feels a bit like a use case that I've been trying to figure out with arch unit so maybe you can tell me if you've got something that could help me here. I'm trying to make sure package infos exist. One thought I've had is look for a class and see if there's an adjacent package info. This feels like somehow it's doing that (in the other direction) which is why I'm putting this question here.

Pps I wonder if this was the source of my null pointer errors in my other ticket. Not sure.