Play Services Resolver for Unity

Overview

This library is intended to be used by any Unity plugin that requires:

• Android specific libraries (e.g AARs).
• iOS CocoaPods.
• Version management of transitive dependencies.

Background

Many Unity plugins have dependencies upon Android specific libraries, iOS CocoaPods, and sometimes have transitive dependencies upon other Unity plugins. This causes the following problems:

• Integrating platform specific (e.g Android and iOS) libraries within a Unity project can be complex and a burden on a Unity plugin maintainer.
• The process of resolving conflicting dependencies on platform specific libraries is pushed to the developer attempting to use a Unity plugin. The developer trying to use you plugin is very likely to give up when faced with Android or iOS specific build errors.
• The process of resolving conflicting Unity plugins (due to shared Unity plugin components) is pushed to the developer attempting to use your Unity plugin. In an effort to resolve conflicts, the developer will very likely attempt to resolve problems by deleting random files in your plugin, report bugs when that doesn't work and finally give up.

The Play Services Resolver plugin (the name comes from its origin of just handling Google Play Services dependencies on Android) provides solutions for each of these problems.

Android Dependency Management

The Android Resolver component of this plugin will download and integrate Android library dependencies and handle any conflicts between plugins that share the same dependencies.

Without the Android Resolver, typically Unity plugins bundle their AAR and JAR dependencies, e.g. a Unity plugin SomePlugin that requires the Google Play Games Android library would redistribute the library and its transitive dependencies in the folder SomePlugin/Android/. When a user imports SomeOtherPlugin that includes the same libraries (potentially at different versions) in SomeOtherPlugin/Android/, the developer using SomePlugin and SomeOtherPlugin will see an error when building for Android that can be hard to interpret.

Using the Android Resolver to manage Android library dependencies:

• Solves Android library conflicts between plugins.
• Handles all of the various processing steps required to use Android libraries (AARs, JARs) in Unity 4.x and above projects. Almost all versions of Unity have - at best - partial support for AARs.
• (Experimental) Supports minification of included Java components without exporting a project.

iOS Dependency Management

The iOS Resolver component of this plugin integrates with CocoaPods to download and integrate iOS libraries and frameworks into the Xcode project Unity generates when building for iOS. Using CocoaPods allows multiple plugins to utilize shared components without forcing developers to fix either duplicate or incompatible versions of libraries included through multiple Unity plugins in their project.

Unity Plugin Version Management

Finally, the Version Handler component of this plugin simplifies the process of managing transitive dependencies of Unity plugins and each plugin's upgrade process.

For example, without the Version Handler plugin, if:

• Unity plugin SomePlugin includes the Play Services Resolver plugin at version 1.1.
• Unity plugin SomeOtherPlugin includes the Play Services Resolver plugin at version 1.2.

The version of Play Services Resolver included in the developer's project depends upon the order the developer imports SomePlugin or SomeOtherPlugin.

This results in:

• Play Services Resolver at version 1.2, if SomePlugin is imported then SomeOtherPlugin is imported.
• Play Services Resolver at version 1.1, if SomeOtherPlugin is imported then SomePlugin is imported.

The Version Handler solves the problem of managing transitive dependencies by:

• Specifying a set of packaging requirements that enable a plugin at different versions to be imported into a Unity project.
• Providing activation logic that selects the latest version of a plugin within a project.

When using the Version Handler to manage Play Services Resolver included in SomePlugin and SomeOtherPlugin, from the prior example, version 1.2 will always be the version activated in a developer's Unity project.

Plugin creators are encouraged to adopt this library to ease integration for their customers. For more information about integrating Play Services Resolver into your own plugin, see the Plugin Redistribution section of this document.

Requirements

The Android Resolver and iOS Resolver components of the plugin only work with Unity version 4.6.8 or higher.

The Version Handler component only works with Unity 5.x or higher as it depends upon the PluginImporter UnityEditor API.

Getting Started

Before you import the Play Services Resolver into your plugin project, you first need to consider whether you intend to redistribute Play Services Resolver along with your own plugin.

Redistributing the Play Services Resolver inside your own plugin will ease the integration process for your users, by resolving dependency conflicts between your plugin and other plugins in a user's project.

If you wish to redistribute the Play Services Resolver inside your plugin, you must follow these steps when importing the play-services-resolver-*.unitypackage, and when exporting your own plugin package:

1. Import the play-services-resolver-*.unitypackage into your plugin project by running Unity from the command line, ensuring that you add the -gvh_disable option.
2. Export your plugin by running Unity from the command line, ensuring that you:
   • Include the contents of the Assets/PlayServicesResolver directory.
   • Add the -gvh_disable option.

You must specify the -gvh_disable option in order for the Version Handler to work correctly!

For example, the following command will import the play-services-resolver-1.2.46.0.unitypackage into the project MyPluginProject and export the entire Assets folder to MyPlugin.unitypackage:

Unity -gvh_disable \
      -batchmode \
      -importPackage play-services-resolver-1.2.46.0.unitypackage \
      -projectPath MyPluginProject \
      -exportPackage Assets MyPlugin.unitypackage \
      -quit

Background

The Version Handler component relies upon deferring the load of editor DLLs so that it can run first and determine the latest version of a plugin component to activate. The build of the Play Services Resolver plugin has Unity asset metadata that is configured so that the editor components are not initially enabled when it's imported into a Unity project. To maintain this configuration when importing the Play Services Resolver .unitypackage into a Unity plugin project, you must specify the command line option -gvh_disable which will prevent the Version Handler component from running and changing the Unity asset metadata.

Android Resolver Usage

The Android Resolver copies specified dependencies from local or remote Maven repositories into the Unity project when a user selects Android as the build target in the Unity editor.

1. Add the play-services-resolver-*.unitypackage to your plugin project (assuming you are developing a plugin). If you are redistributing the Play Services Resolver with your plugin, you must follow the import steps in the Getting Started section!

2. Copy and rename the SampleDependencies.xml file into your plugin and add the dependencies your plugin requires.

   The XML file just needs to be under an Editor directory and match the name *Dependencies.xml. For example, MyPlugin/Editor/MyPluginDependencies.xml.

3. Follow the steps in the Getting Started section when you are exporting your plugin package.

For example, to add the Google Play Games library (com.google.android.gms:play-services-games package) at version 9.8.0 to the set of a plugin's Android dependencies:

<dependencies>
  <androidPackages>
    <androidPackage spec="com.google.android.gms:play-services-games:9.8.0">
      <androidSdkPackageIds>
        <androidSdkPackageId>extra-google-m2repository</androidSdkPackageId>
      </androidSdkPackageIds>
    </androidPackage>
  </androidPackages>
</dependencies>

The version specification (last component) supports:

• Specific versions e.g 9.8.0
• Partial matches e.g 9.8.+ would match 9.8.0, 9.8.1 etc. choosing the most recent version.
• Latest version using LATEST or +. We do not recommend using this unless you're 100% sure the library you depend upon will not break your Unity plugin in future.

The above example specifies the dependency as a component of the Android SDK manager such that the Android SDK manager will be executed to install the package if it's not found. If your Android dependency is located on Maven central it's possible to specify the package simply using the androidPackage element:

<dependencies>
  <androidPackages>
    <androidPackage spec="com.google.api-client:google-api-client-android:1.22.0" />
  </androidPackages>
</dependencies>

Auto-resolution

By default the Android Resolver automatically monitors the dependencies you have specified and the Plugins/Android folder of your Unity project. The resolution process runs when the specified dependencies are not present in your project.

The auto-resolution process can be disabled via the Assets > Play Services Resolver > Android Resolver > Settings menu.

Manual resolution can be performed using the following menu options:

• Assets > Play Services Resolver > Android Resolver > Resolve
• Assets > Play Services Resolver > Android Resolver > Force Resolve

Android Manifest Variable Processing

Some AAR files (for example play-services-measurement) contain variables that are processed by the Android Gradle plugin. Unfortunately, Unity does not perform the same processing when using Unity's Internal Build System, so the Android Resolver plugin handles known cases of this variable substitution by exploding the AAR into a folder and replacing ${applicationId} with the bundleID.

Disabling AAR explosion and therefore Android manifest processing can be done via the Assets > Play Services Resolver > Android Resolver > Settings menu. You may want to disable explosion of AARs if you're exporting a project to be built with Gradle / Android Studio.

ABI Stripping

Some AAR files contain native libraries (.so files) for each ABI supported by Android. Unfortunately, when targeting a single ABI (e.g x86), Unity does not strip native libraries for unused ABIs. To strip unused ABIs, the Android Resolver plugin explodes an AAR into a folder and removes unused ABIs to reduce the built APK size. Furthermore, if native libraries are not stripped from an APK (e.g you have a mix of Unity's x86 library and some armeabi-v7a libraries) Android may attempt to load the wrong library for the current runtime ABI completely breaking your plugin when targeting some architectures.

AAR explosion and therefore ABI stripping can be disabled via the Assets > Play Services Resolver > Android Resolver > Settings menu. You may want to disable explosion of AARs if you're exporting a project to be built with Gradle / Android Studio.

Resolution Strategies

By default the Android Resolver will use Gradle to download dependencies prior to integrating them into a Unity project. This works with Unity's internal build system and Gradle / Android Studio project export.

It's possible to change the resolution strategy via the Assets > Play Services Resolver > Android Resolver > Settings menu.

Dependency Tracking

The Android Resolver creates the ProjectSettings/AndroidResolverDependencies.xml to quickly determine the set of resolved dependencies in a project. This is used by the auto-resolution process to only run the expensive resolution process when necessary.

iOS Resolver Usage

The iOS resolver component of this plugin manages CocoaPods. A CocoaPods Podfile is generated and the pod tool is executed as a post build process step to add dependencies to the Xcode project exported by Unity.

Dependencies for iOS are added by referring to CocoaPods.

1. Add the play-services-resolver-*.unitypackage to your plugin project (assuming you are developing a plugin). If you are redistributing the Play Services Resolver with your plugin, you must follow the import steps in the Getting Started section!

2. Copy and rename the SampleDependencies.xml file into your plugin and add the dependencies your plugin requires.

   The XML file just needs to be under an Editor directory and match the name *Dependencies.xml. For example, MyPlugin/Editor/MyPluginDependencies.xml.

3. Follow the steps in the Getting Started section when you are exporting your plugin package.

For example, to add the AdMob pod, version 7.0 or greater with bitcode enabled:

<dependencies>
  <iosPods>
    <iosPod name="Google-Mobile-Ads-SDK" version="~> 7.0" bitcodeEnabled="true"
            minTargetSdk="6.0" />
  </iosPods>
</dependencies>

Integration Strategies

The CocoaPods are either:

• Downloaded and injected into the Xcode project file directly, rather than creating a separate xcworkspace. We call this Xcode project integration.
• If the Unity version supports opening a xcworkspace file, the pod tool is used as intended to generate a xcworkspace which references the CocoaPods. We call this Xcode workspace integration.

The resolution strategy can be changed via the Assets > Play Services Resolver > iOS Resolver > Settings menu.

Version Handler Usage

The Version Handler component of this plugin manages:

• Shared Unity plugin dependencies.
• Upgrading Unity plugins by cleaning up old files from previous versions.

Unity plugins can be managed by the Version Handler using the following steps:

1. Add the gvh asset label to each asset (file) you want Version Handler to manage.
2. Add the gvh_version-VERSION label to each asset where VERSION is the version of the plugin you're releasing (e.g 1.2.3).
3. Optional: Add gvh_targets-editor label to each editor DLL in your plugin and disable editor as a target platform for the DLL. The Version Handler will enable the most recent version of this DLL when the plugin is imported.
4. Optional: If your plugin is included in other Unity plugins, you should add the version number to each filename and change the GUID of each asset. This allows multiple versions of your plugin to be imported into a Unity project, with the Version Handler component activating only the most recent version.
5. Create a manifest text file named MY_UNIQUE_PLUGIN_NAME_VERSION.txt that lists all the files in your plugin relative to the project root. Then add the gvh_manifest label to the asset to indicate this file is a plugin manifest.
6. Redistribute the Play Services Resolver Unity plugin with your plugin. See the Plugin Redistribution for the details.

If you follow these steps:

• When users import a newer version of your plugin, files referenced by the older version's manifest are cleaned up.
• The latest version of the plugin will be selected when users import multiple packages that include your plugin, assuming the steps in Plugin Redistribution are followed.

Building from Source

To build this plugin from source you need the following tools installed:

• Unity (with iOS and Android modules installed)

You can build the plugin by running the following from your shell (Linux / OSX):

./gradlew build

or Windows:

./gradlew.bat build

Releasing

Each time a new build of this plugin is checked into the source tree you need to do the following:

• Bump the plugin version variable pluginVersion in build.gradle
• Update CHANGELOG.md with the new version number and changes included in the release.
• Build the release using ./gradle release which performs the following:
  • Updates play-services-resolver-*.unitypackage
  • Copies the unpacked plugin to the exploded directory.
  • Updates template metadata files in the plugin directory. The GUIDs of all asset metadata is modified due to the version number change. Each file within the plugin is versioned to allow multiple versions of the plugin to be imported into a Unity project which allows the most recent version to be activated by the Version Handler component.
• Create the release commit and tag the release using ./gradle gitTagRelease which performs the following:
  • git add -A to pick up all modified, new and deleted files in the tree.
  • git commit --amend -a to create a release commit with the release notes in the change log.
  • git tag -a RELEASE -m "version RELEASE" to tag the release.