Kotlin generates a `.kotlin_module` file for each ...

# gradle

[ansman]

Kotlin generates a .kotlin_module file for each compiled module. The name of the file is the name of the module, but this can cause some issues when you have multiple modules with the same name (but different paths). Would it be worth filing a feature request to use the path instead of the module name?

[Chris Lee]

The problem extends well beyond this file; many parts of Gradle have issues when there are modules with the same name, in different paths. The best solution is to avoid this:
• name modules uniquely, where possible;
• adjust the group or project name to include the pathing, in some manner (this may not address all issues, but works fine in several large projects I have)

[mbonnin]

Shouldn't different modules generate different .jar/.aar and the compiler be able to know/link the .kotlin_module info to only those symbols that are in the jar?

[mbonnin]

I can see how that's an issue for fat jars but in the "regular" case, it could work?

[Chris Lee]

I’ve never run into a problem with .kotlin_module with overlapping module names, rather other challenges such as confusion when pulling project dependencies etc.

[ansman]

The issue is that these files get packaged into a single APK on Android so they'll overwrite each other

[mbonnin]

But that's executable form, you're not supposed to compile against an APK, right?

[mbonnin]

Unless .kotlin_module is used for something else?

[ansman]

Supposedly it is used for some things as it's recommended to exclude them from the APK

[ansman]

The same issue happens with an AAR though

[ansman]

I think setting this file name yourself using moduleName is the best bet here

[Chris Lee]

don’t know Android / APK that well but often build tasks that assemble multiple components (e.g. fat jars) there are options to customize merging, instead of blindly overwriting.

[ansman]

Unfortunately, the kotlin_module are special cased in the Android Gradle Plugin so the normal packaging options doesn't apply to them

[Chris Lee]

It seems like the recommendation is to exclude these from the APK, would that not address the issue?

[ansman]

I'm not sure using packaging options work here. But also, we do want them since we do use kotlin-reflect

[mbonnin]

ah, reflection

[Chris Lee]

Perhaps something like this then:

Since the actual names of the *.kotlin_module files do not affect anything at the moment, you can try to rename one of the files during build so that the names are different (the new name should still end with .kotlin_module). I’m not sure what is the best way to do this in your particular case, though. You might want to exclude the *.kotlin_module files using packagingOptions and add a custom task that extracts the files and puts them as resources, renaming one of them, so that both are included.

[mbonnin]

Why is it it's always reflection 😄

[Chris Lee]

It’s always reflection 😉 well, or the firewall 😡

[ansman]

You don't need to rename them, you can set the name directly using compileOptions.moduleName

[Chris Lee]

excellent.

[ansman]

I'm guessing something in the generated code also references that file name. Otherwise kotlin-reflect would have to list all kotlin_module files

[ansman]

Which to be fair it might

[Chris Lee]

from that comment it indicates the name is not currently used.

[Chris Lee]

It should all line-up if you use compileOptions.moduleName

[ansman]

I ended up adding this to our convention plugin:

tasks.withType<KotlinCompile>().configureEach {
    compilerOptions {
        moduleName.set(path.removePrefix(":").replace(":", "_"))
    }
}

[Chris Lee]

fwiw have this snippet to make modules unique when it comes to GAV coordinates (in a convention plugin for each module):
_group_ = "<prefix>" + _project_._path_._split_(":")._dropLast_(1)._joinToString_(".")