Dokka fails after encountering an empty subproject

[Laxystem]

Describe the bug
When declaring a gradle project like this:

// settings.gradle.kts
include("api:common")

Dokka will try to generate documentation for api, and fail.

Expected behaviour
Dokka will skip api.
Screenshots

> Task :api:dokkaHtmlMultiModule FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Some problems were found with the configuration of task ':api:dokkaHtmlMultiModule' (type 'DokkaMultiModuleTask').
  - Gradle detected a problem with the following location: '/home/laxystem/Projects/Gimli/api/client/build/dokka/htmlPartial'.
    
    Reason: Task ':api:dokkaHtmlMultiModule' uses this output of task ':dokkaHtmlMultiModule' without declaring an explicit or implicit dependency. This can lead to incorrect results being produced, depending on what order the tasks are executed.
    
    Possible solutions:
      1. Declare task ':dokkaHtmlMultiModule' as an input of ':api:dokkaHtmlMultiModule'.
      2. Declare an explicit dependency on ':dokkaHtmlMultiModule' from ':api:dokkaHtmlMultiModule' using Task#dependsOn.
      3. Declare an explicit dependency on ':dokkaHtmlMultiModule' from ':api:dokkaHtmlMultiModule' using Task#mustRunAfter.
    
    For more information, please refer to https://docs.gradle.org/8.6/userguide/validation_problems.html#implicit_dependency in the Gradle documentation.
  - Gradle detected a problem with the following location: '/home/laxystem/Projects/Gimli/api/common/build/dokka/htmlPartial'.
    
    Reason: Task ':api:dokkaHtmlMultiModule' uses this output of task ':dokkaHtmlMultiModule' without declaring an explicit or implicit dependency. This can lead to incorrect results being produced, depending on what order the tasks are executed.
    
    Possible solutions:
      1. Declare task ':dokkaHtmlMultiModule' as an input of ':api:dokkaHtmlMultiModule'.
      2. Declare an explicit dependency on ':dokkaHtmlMultiModule' from ':api:dokkaHtmlMultiModule' using Task#dependsOn.
      3. Declare an explicit dependency on ':dokkaHtmlMultiModule' from ':api:dokkaHtmlMultiModule' using Task#mustRunAfter.
    
    For more information, please refer to https://docs.gradle.org/8.6/userguide/validation_problems.html#implicit_dependency in the Gradle documentation.
  - Gradle detected a problem with the following location: '/home/laxystem/Projects/Gimli/api/server/build/dokka/htmlPartial'.
    
    Reason: Task ':api:dokkaHtmlMultiModule' uses this output of task ':dokkaHtmlMultiModule' without declaring an explicit or implicit dependency. This can lead to incorrect results being produced, depending on what order the tasks are executed.
    
    Possible solutions:
      1. Declare task ':dokkaHtmlMultiModule' as an input of ':api:dokkaHtmlMultiModule'.
      2. Declare an explicit dependency on ':dokkaHtmlMultiModule' from ':api:dokkaHtmlMultiModule' using Task#dependsOn.
      3. Declare an explicit dependency on ':dokkaHtmlMultiModule' from ':api:dokkaHtmlMultiModule' using Task#mustRunAfter.
    
    For more information, please refer to https://docs.gradle.org/8.6/userguide/validation_problems.html#implicit_dependency in the Gradle documentation.

To Reproduce
There's a sample project on codeberg.

Dokka configuration

none yet

Installation

• Operating system: Linux
• Build tool: Gradle v6.8.0
• Dokka version: 1.9.10

[Laxystem]

Found workaround.

plugins {
    kotlin("multiplatform")
    id("org.jetbrains.dokka")
}

// top-level build.gradle.kts
allprojects {
    subprojects.forEach {
        if (it.subprojects.isNotEmpty()) tasks.dokkaHtmlMultiModule {
            dependsOn(it.tasks.dokkaHtmlMultiModule)
        }
    }
}

I was wrong, this happens because dokka doesn't know what should depend on what.

[vmishenev]

It looks like a duplication of #2954

Found workaround.

Yes, it is a possible solution.
There is also a simpler workaround #2954 (comment)