Read build script blocks from gradle plugin - gradle

Question

There is a gradle plugin with id ("com.my.plugin").
The project using this plugin has the following build.gradle file:
...
apply plugin: 'com.my.plugin'
...
android {
    ...
    defaultConfig {
        ...
        testInstrumentationRunner "com.my.plugin.junit4.MyCustomRunner"
        ...
    }
    ...
}
...
dependencies {
    ...
    androidTestImplementation com.my:plugin-junit4:1.0.0-alpha04
    ...
}
...
The class implementing the plugin is as follows:
class MyPlugin: Plugin <Project> {
    override fun apply (project: Project) {
        project.afterEvaluate {
            // here I need to read testInstrumentationRunner value declared
            // in the defaultConfig block of the build.gradle file
            // also here I need to read androidTestImplementation value declared
            // in the dependencies block of the build.gradle file
        }
    }
}
In the project.afterEvaluate {...} block of the plugin I need to check for the values ​​of testInstrumentationRunner and androidTestImplementation declared in the build.gradle file of the project using this plugin. How to do it?

Answer 1

Since you're using Kotlin for your plugin implementation, you'll need know the type of the android { } extension. Otherwise you will run into compilation errors.
Essentially, you need to retrieve a reference of the android extension in your plugin like so:
project.afterEvaluate {
// we don't know the concrete type so this will be `Object` or `Any`
val android = project.extensions.getByName("android")
println(android::class.java) // figure out the type
// assume we know the type now
val typedAndroid = project.extensions.getByType(WhateverTheType::class.java)
// Ok now Kotlin knows of the type and its properties
println(typedAndroid.defaultConfig.testInstrumentationRunner)
}
I'm not familar with Android or its Gradle plugin. Google only led me to its Javadocs here which didn't help. So the above may or may not work.