Gradle task to strip unused packages on Google Play Services library

strip_play_services.gradle

def toCamelCase(String string) {
    String result = ""
    string.findAll("[^\\W]+") { String word ->
        result += word.capitalize()
    }
    return result
}

afterEvaluate { project ->
    Configuration runtimeConfiguration = project.configurations.getByName('compile')
    ResolutionResult resolution = runtimeConfiguration.incoming.resolutionResult
    // Forces resolve of configuration
    ModuleVersionIdentifier module = resolution.getAllComponents().find { it.moduleVersion.name.equals("play-services") }.moduleVersion

    String prepareTaskName = "prepare${toCamelCase("${module.group} ${module.name} ${module.version}")}Library"
    File playServiceRootFolder = project.tasks.find { it.name.equals(prepareTaskName) }.explodedDir

    Task stripPlayServices = project.tasks.create(name: 'stripPlayServices', group: "Strip") {
        inputs.files new File(playServiceRootFolder, "classes.jar")
        outputs.dir playServiceRootFolder
        description 'Strip useless packages from Google Play Services library to avoid reaching dex limit'

        doLast {
            copy {
                from(file(new File(playServiceRootFolder, "classes.jar")))
                into(file(playServiceRootFolder))
                rename { fileName ->
                    fileName = "classes_orig.jar"
                }
            }
            tasks.create(name: "stripPlayServices" + module.version, type: Jar) {
                destinationDir = playServiceRootFolder
                archiveName = "classes.jar"
                from(zipTree(new File(playServiceRootFolder, "classes_orig.jar"))) {
                    exclude "com/google/ads/**"
                    exclude "com/google/android/gms/analytics/**"
                    exclude "com/google/android/gms/games/**"
                    exclude "com/google/android/gms/plus/**"
                    exclude "com/google/android/gms/drive/**"
                    exclude "com/google/android/gms/ads/**"
                }
            }.execute()
            delete file(new File(playServiceRootFolder, "classes_orig.jar"))
        }
    }

    project.tasks.findAll { it.name.startsWith('prepare') && it.name.endsWith('Dependencies') }.each { Task task ->
        task.dependsOn stripPlayServices
    }
}

With the latest 6.x of gms you might need to add the following to keep the class count to a minimum:

                exclude "com/google/android/gms/fitness/**"
                exclude "com/google/android/gms/wearable/**"
                exclude "com/google/android/gms/wallet/**"
                exclude "com/google/android/gms/cast/**"
                exclude "com/google/android/gms/ads/doubleclick/**"
                exclude "com/google/android/gms/ads/mediation/**"
                exclude "com/google/android/gms/ads/purchase/**"
                exclude "com/google/android/gms/ads/search/**"
                exclude "com/google/android/gms/analytics/ecommerce/**"
                exclude "com/google/android/gms/common/images/**"

Can you explain for dummies where to put this script (in module build.gradle or in application build.gradle) and how to run it.
Because I put it in module build.gradle and get the following error
Error:(157) Execution failed for task ':phase-android-beta:stripPlayServices'.

Cannot expand ZIP 'D:\Projects\phase\phase-android-beta\build\intermediates\exploded-aar\com.google.android.gms\play-services\6.1.71\classes_orig.jar' as it does not exist.

I fix it me helped @techfreak comment:
In case anyone needs this to make this work when using parallel builds (org.gradle.parallel=true inside gradle.properties), you need to add this snippet at the end :

project.tasks.findAll {  it.name.contains(prepareTaskName) }.each { Task task ->
    stripPlayServices.mustRunAfter task
}

I've created a fork with this modification here https://gist.github.com/TechFreak/f7ffcbfee5cfe318d31a: but I would prefer if the author added my modifications back to keep everything in one place

Google released GooglePlayServicesLib 6.5 you can now only compile the parts of GooglePlayServices you need http://android-developers.blogspot.de/2014/11/google-play-services-65.html

Starting with version 6.5, of Google Play services, you’ll be able to pick from a number of individual APIs, and you can see which ones have their own include files in the documentation. For example, if all you want to use is Maps, you would instead have:

  compile 'com.google.android.gms:play-services-maps:6.5.87'

Note that this will transitively include the ‘base’ libraries, which are used across all APIs. You can include them independently with the following line:

  compile 'com.google.android.gms:play-services-base:6.5.87'

http://android-developers.blogspot.de/2014/12/google-play-services-and-dex-method.html

Google Play services API	Description in build.gradle
Google+	com.google.android.gms:play-services-plus:6.5.+
Google Account Login	com.google.android.gms:play-services-identity:6.5.+
Google Activity Recognition	com.google.android.gms:play-services-location:6.5.+
Google App Indexing	com.google.android.gms:play-services-appindexing:6.5.+
Google Cast	com.google.android.gms:play-services-cast:6.5.+
Google Drive	com.google.android.gms:play-services-drive:6.5.+
Google Fit	com.google.android.gms:play-services-fitness:6.5.+
Google Maps	com.google.android.gms:play-services-maps:6.5.+
Google Mobile Ads	com.google.android.gms:play-services-ads:6.5.+
Google Panorama Viewer	com.google.android.gms:play-services-panorama:6.5.+
Google Play Game services	com.google.android.gms:play-services-games:6.5.+
Google Wallet	com.google.android.gms:play-services-wallet:6.5.+
Android Wear	com.google.android.gms:play-services-wearable:6.5.+
Google Actions Google Analytics Google Cloud Messaging	com.google.android.gms:play-services-base:6

If you don't want to use play services 6.5+ try this:

compile('com.google.android.gms:play-services:6.1.71') {
        exclude group: "com/google/ads/**"
        exclude group: "com/google/android/gms/analytics/**"
        exclude group: "com/google/android/gms/games/**"
        exclude group: "com/google/android/gms/maps/**"
        exclude group: "com/google/android/gms/panorama/**"
        exclude group: "com/google/android/gms/plus/**"
        exclude group: "com/google/android/gms/drive/**"
        exclude group: "com/google/android/gms/ads/**"
        exclude group: "com/google/android/gms/wallet/**"
        exclude group: "com/google/android/gms/wearable/**"
}

I am trying to get rid of the unused library for Google Play services 7.3 with the previous code but it does not work.

This is the code:

    compile ('com.google.android.gms:play-services:7.3.+') {
        exclude group: "com/google/ads/**"
        exclude group: "com/google/android/gms/ads/**"
        exclude group: "com/google/android/gms/analytics/**"
        exclude group: "com/google/android/gms/appindexing/**"
        exclude group: "com/google/android/gms/appinvite/**"
        exclude group: "com/google/android/gms/appstate/**"
        exclude group: "com/google/android/gms/cast/**"
        exclude group: "com/google/android/gms/drive/**"
        exclude group: "com/google/android/gms/fitness/**"
        exclude group: "com/google/android/gms/games/**"
        exclude group: "com/google/android/gms/identity/**"
        exclude group: "com/google/android/gms/location/**"
        exclude group: "com/google/android/gms/maps/**"
        exclude group: "com/google/android/gms/nearby/**"
        exclude group: "com/google/android/gms/panorama/**"
        exclude group: "com/google/android/gms/plus/**"
        exclude group: "com/google/android/gms/safetynet/**"
        exclude group: "com/google/android/gms/wallet/**"
        exclude group: "com/google/android/gms/wearable/**"
    }

And I still can see them in the console:

:app:prepareComGoogleAndroidGmsPlayServices730Library
:app:prepareComGoogleAndroidGmsPlayServicesAds730Library
:app:prepareComGoogleAndroidGmsPlayServicesAnalytics730Library
:app:prepareComGoogleAndroidGmsPlayServicesAppindexing730Library
:app:prepareComGoogleAndroidGmsPlayServicesAppinvite730Library
:app:prepareComGoogleAndroidGmsPlayServicesAppstate730Library
:app:prepareComGoogleAndroidGmsPlayServicesBase730Library
:app:prepareComGoogleAndroidGmsPlayServicesCast730Library
:app:prepareComGoogleAndroidGmsPlayServicesDrive730Library
:app:prepareComGoogleAndroidGmsPlayServicesFitness730Library
:app:prepareComGoogleAndroidGmsPlayServicesGames730Library
:app:prepareComGoogleAndroidGmsPlayServicesGcm730Library
:app:prepareComGoogleAndroidGmsPlayServicesIdentity730Library
:app:prepareComGoogleAndroidGmsPlayServicesLocation730Library
:app:prepareComGoogleAndroidGmsPlayServicesMaps730Library
:app:prepareComGoogleAndroidGmsPlayServicesNearby730Library
:app:prepareComGoogleAndroidGmsPlayServicesPanorama730Library
:app:prepareComGoogleAndroidGmsPlayServicesPlus730Library
:app:prepareComGoogleAndroidGmsPlayServicesSafetynet730Library
:app:prepareComGoogleAndroidGmsPlayServicesWallet730Library
:app:prepareComGoogleAndroidGmsPlayServicesWearable730Library

What am I doing wrong?

As of Play service 8.3.0 you can selectively choose which individual library used in the app. So there's no need to exclude anymore.
https://developers.google.com/android/guides/setup#split

I paste it to the bottom of app's build.gradle file and it failed : "Cannot get property 'moduleVersion' on null object"
What should I do ?

Cannot get property 'moduleVersion' on null object. I got this problem and the sync failed....

Cannot get property 'moduleVersion' on null object. I got this problem and the sync failed....

at
ModuleVersionIdentifier module = resolution.getAllComponents().find { it.moduleVersion.name.equals("play-services") }.moduleVersion

Happened to me to, so I printed it:
`

ModuleVersionIdentifier module = resolution.getAllComponents().find {
    System.out.println("MODULE NAME ====> " + it.moduleVersion.name);
    /*it.moduleVersion.name.equals("play-services")*/
}.moduleVersion

`
....
MODULE NAME ====> recyclerview-v7
MODULE NAME ====> core
MODULE NAME ====> gson
MODULE NAME ====> hirondelle-date4j
MODULE NAME ====> play-services-analytics
:app:preBuild
:jawampaLib:preBuild
....

As You can see, there is no "play-services", but "play-services-analytics" (in my case) :)

Same happens in my case.