Android gradle multiproject dependency resolution

Question

In my Android project I have a task for copying the build dependencies to an external directory as below:

task copyBuildDependencies(type: Copy) {
    delete "$buildDir/dependencies"
    afterEvaluate {
        from configurations.releaseCompileClasspath
        into "$buildDir/dependencies"

        doLast {
            FileTree files = fileTree("$buildDir/dependencies")
            files.forEach { file ->
                if (file.isFile() && file.name.endsWith(".aar")) {
                    copy {
                        from zipTree(file).matching { include "*.jar" }
                        into "$buildDir/dependencies"
                        eachFile {
                            it.path = it.path.replace(it.name, "${file.name}-${it.name}")
                        }
                    }
                }
            }
        }
    }
}

I have normal dependencies with project dependencies:

dependencies {
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    ...
    implementation 'com.google.guava:guava:11.0.2'
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:0.22.5'
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:0.22.5'
    // Note: These are Android Library projects
    implementation project(':genericutils')
    implementation project(':module2')
    ...
}

When I run the task copyBuildDependencies I get the following error:

Executing task 'copyBuildDependencies'...

Executing tasks: [copyBuildDependencies]

Configuration on demand is an incubating feature.

FAILURE: Build failed with an exception.

* What went wrong:
Could not determine the dependencies of task ':BiometricInterfaceLib:copyBuildDependencies'.
> Could not resolve all task dependencies for configuration ':BiometricInterfaceLib:releaseCompileClasspath'.
> More than one variant of project :genericutils matches the consumer attributes:
    - Configuration ':genericutils:releaseApiElements' variant android-aidl:
        - Found artifactType 'android-aidl' but wasn't required.
        - Required com.android.build.api.attributes.BuildTypeAttr 'release' and found compatible value 'release'.
        - Found com.android.build.api.attributes.VariantAttr 'release' but wasn't required.
        - Required com.android.build.gradle.internal.dependency.AndroidTypeAttr 'Aar' and found compatible value 'Aar'.
        - Required org.gradle.usage 'java-api' and found compatible value 'java-api'.
    - Configuration ':genericutils:releaseApiElements' variant android-classes:
        - Found artifactType 'android-classes' but wasn't required.
        - Required com.android.build.api.attributes.BuildTypeAttr 'release' and found compatible value 'release'.
        - Found com.android.build.api.attributes.VariantAttr 'release' but wasn't required.
        - Required com.android.build.gradle.internal.dependency.AndroidTypeAttr 'Aar' and found compatible value 'Aar'.
        - Required org.gradle.usage 'java-api' and found compatible value 'java-api'.
    - Configuration ':genericutils:releaseApiElements' variant android-manifest:
        - Found artifactType 'android-manifest' but wasn't required.
        - Required com.android.build.api.attributes.BuildTypeAttr 'release' and found compatible value 'release'.
        - Found com.android.build.api.attributes.VariantAttr 'release' but wasn't required.
        - Required com.android.build.gradle.internal.dependency.AndroidTypeAttr 'Aar' and found compatible value 'Aar'.
        - Required org.gradle.usage 'java-api' and found compatible value 'java-api'.
    - Configuration ':genericutils:releaseApiElements' variant android-renderscript:
        - Found artifactType 'android-renderscript' but wasn't required.
        - Required com.android.build.api.attributes.BuildTypeAttr 'release' and found compatible value 'release'.
        - Found com.android.build.api.attributes.VariantAttr 'release' but wasn't required.
        - Required com.android.build.gradle.internal.dependency.AndroidTypeAttr 'Aar' and found compatible value 'Aar'.
        - Required org.gradle.usage 'java-api' and found compatible value 'java-api'.
    - Configuration ':genericutils:releaseApiElements' variant jar:
        - Found artifactType 'jar' but wasn't required.
        - Required com.android.build.api.attributes.BuildTypeAttr 'release' and found compatible value 'release'.
        - Found com.android.build.api.attributes.VariantAttr 'release' but wasn't required.
        - Required com.android.build.gradle.internal.dependency.AndroidTypeAttr 'Aar' and found compatible value 'Aar'.
        - Required org.gradle.usage 'java-api' and found compatible value 'java-api'.
> More than one variant of project :module2 matches the consumer attributes:
    - Configuration ':module2:releaseApiElements' variant android-aidl:
        - Found artifactType 'android-aidl' but wasn't required.
        - Required com.android.build.api.attributes.BuildTypeAttr 'release' and found compatible value 'release'.
        - Found com.android.build.api.attributes.VariantAttr 'release' but wasn't required.
        - Required com.android.build.gradle.internal.dependency.AndroidTypeAttr 'Aar' and found compatible value 'Aar'.
        - Required org.gradle.usage 'java-api' and found compatible value 'java-api'.
    - Configuration ':module2:releaseApiElements' variant android-classes:
        - Found artifactType 'android-classes' but wasn't required.
        - Required com.android.build.api.attributes.BuildTypeAttr 'release' and found compatible value 'release'.
        - Found com.android.build.api.attributes.VariantAttr 'release' but wasn't required.
        - Required com.android.build.gradle.internal.dependency.AndroidTypeAttr 'Aar' and found compatible value 'Aar'.
        - Required org.gradle.usage 'java-api' and found compatible value 'java-api'.
    - Configuration ':module2:releaseApiElements' variant android-manifest:
        - Found artifactType 'android-manifest' but wasn't required.
        - Required com.android.build.api.attributes.BuildTypeAttr 'release' and found compatible value 'release'.
        - Found com.android.build.api.attributes.VariantAttr 'release' but wasn't required.
        - Required com.android.build.gradle.internal.dependency.AndroidTypeAttr 'Aar' and found compatible value 'Aar'.
        - Required org.gradle.usage 'java-api' and found compatible value 'java-api'.
    - Configuration ':module2:releaseApiElements' variant android-renderscript:
        - Found artifactType 'android-renderscript' but wasn't required.
        - Required com.android.build.api.attributes.BuildTypeAttr 'release' and found compatible value 'release'.
        - Found com.android.build.api.attributes.VariantAttr 'release' but wasn't required.
        - Required com.android.build.gradle.internal.dependency.AndroidTypeAttr 'Aar' and found compatible value 'Aar'.
        - Required org.gradle.usage 'java-api' and found compatible value 'java-api'.
    - Configuration ':module2:releaseApiElements' variant jar:
        - Found artifactType 'jar' but wasn't required.
        - Required com.android.build.api.attributes.BuildTypeAttr 'release' and found compatible value 'release'.
        - Found com.android.build.api.attributes.VariantAttr 'release' but wasn't required.
        - Required com.android.build.gradle.internal.dependency.AndroidTypeAttr 'Aar' and found compatible value 'Aar'.
        - Required org.gradle.usage 'java-api' and found compatible value 'java-api'.

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

BUILD FAILED in 2s
16:39:07: Task execution finished 'copyBuildDependencies'.

I can use the exclude module option on configurations.releaseCompileClasspath but then the assembleRelease task fails because it can not find the dependencies.

Edit: I have created an example project to help show the result that I am after and the issue I am having: https://gitlab.com/crunchy234/android-gradle-dependencies-export

--- Edit 2 ---

The reason for wanting the dependencies of the library module rather than the Jar for the library is so that a Xamarin Bindings library can be created.

So what is wanted for the Xamarin Bindings is the AAR for the library (mastermodule in the case of the example code) and all of the Jars for the libraries dependencies. E.g:

mastermodule/build/dependencies/
├── animated-vector-drawable-28.0.0-alpha3.aar-classes.jar
├── annotations-13.0.jar
...
├── collections-28.0.0-alpha3.jar
├── common-1.1.1.jar
├── coordinatorlayout-28.0.0-alpha3.aar-classes.jar
...
etc

Answer 1

If I understand correctly

1. your project is an Android library project.
2. your copy task tries to copy all the jars inside the AAR library.
3. rename the classes.jar.

Probably below is what you want. Add this into the build.gradle under root project.

// Add this into the build.gradle under **root** project.
// Add the modules that you want to exclude from having this copyXXXJar task.
def modulesExcluded = [
        'app',
        'mastermodulewantedoutput'
]

subprojects { prj ->

    // Skip excluded modules
    if (modulesExcluded.contains(prj.name)) {
        prj.afterEvaluate {
            tasks['preBuild'].dependsOn(copyModuleJars)
        }
        return
    }

    prj.afterEvaluate {

        /**
         * Dynamically create task "copyXXXJar" according to build variant of each library module.
         */
        android.libraryVariants.all { variant ->

            def capitalizedVariantName = variant.name.capitalize()
            def variantName = variant.flavorName
            if (!variantName || variantName == "") {
                variantName = variant.buildType.name
            } else {
                variantName += "-${variant.buildType.name}"
            }
            //================================================================================
            // Define build/copy variant jar and copy to dependencies
            //================================================================================
            def copyJarTask = project.tasks.create("copy${capitalizedVariantName}Jar", Copy) {
                group "Copy Jar"
                description "Rename the classes.jar to ${project.name}-${variantName}.jar and copy it into dist folder."


                def fromDirModule = "$buildDir/outputs/aar/${project.name}-${variantName}.aar"
                def intoDirModule = "$rootDir/dependencies/$variant.buildType.name"
                from(zipTree(fromDirModule))
                into(intoDirModule)
                include('*.jar')
                include('libs/*.jar')
                rename('classes.jar', "${project.name}-${variantName}.jar")

                dependsOn "assemble${capitalizedVariantName}"
            }
            copyModuleJars.dependsOn(copyJarTask)
        }
    }
}

// Task to copy all the modules' jars. It can be run with command [ ./gradlew copyModuleJars ]
task copyModuleJars {
    group = 'Copy Jar'
    description = 'Copy the classes.jar from each module.'
} 

Run below command to verify

./gradlew copyModuleJars

Hope it helps.

--------- Edited ----------

I checked your gitlab project. It looks you only need the jar inside the .aar. I'd like to say this may cause some problems because you drop the associated res files, aidl file, assets and R.txt, etc which are considered as necessary parts of the .aar library. For example, one of your dependency aar appcompat-v7-28.0.0-alpha3, will actually have below layout when you unzip it, NOT ONLY the classes.jar.

Additionally, you can simply modify the modulesExcluded array as I edited above. And the condition check of "hasProperty()" can be removed.

The output will be under "$rootDir/dependencies". Something like below:

• debug
  • genericutils-debug.jar
  • mastermodule-debug.jar
• release
  • genericutils-release.jar
  • mastermodule-release.jar

These jars are generated from your own source code, i.e. your genericutils and mastermodule sources. If the transitive dependencies of library are in ".jar" format, they will go into "libs/" of the .aar, if they are in ".aar" format, i don't think you can simply pick its classes.jar but strip its associated and necessary parts unless you have some special requirement and those missing part don't matter with your project.

-------- Edited 2 ---------

In case that you only concern about the source code and don't use any resources (res, R.txt, aidl, jni etc) inside your code logic, e.g. probably your genericutils module will be such kind of case, then you can simply pick up the classes.jar only. It won't cause any issue when you use it as a normal Java library.