android.registerTransform doesn't work when called from apply from: 'other.gradle'

[Malcolm Evershed]

My app/build.gradle says at the end "apply from: 'other.gradle'". The other.gradle file is very simple and contains the following:

buildscript {

    repositories {

        jcenter()

    }

    dependencies {

        // Needed for com.android.build.api classes

        classpath 'com.android.tools.build:gradle-api:2.3.1'

    }

}

import com.android.build.api.transform.QualifiedContent

import com.android.build.api.transform.Transform

// Stub implementation

class MyTransform extends Transform {

    @Override

    String getName() {

        return null

    }

    @Override

    Set<QualifiedContent.ContentType> getInputTypes() {

        return null

    }

    @Override

    Set<QualifiedContent.Scope> getScopes() {

        return null

    }

    @Override

    boolean isIncremental() {

        return false

    }

}

Class parameterClass

for (def method : android.getClass().getMethods()) {

    if (method.getName() == "registerTransform") {

        parameterClass = method.getParameterTypes()[0]

        println 'Class of first parameter to android.registerTransform: ' + parameterClass

    }

}

Class superClass = MyTransform.class.getSuperclass()

println 'Class of parameter that we want to pass to android.registerTransform: ' + superClass

println 'Are the names of the two types equal? ' + superClass.getCanonicalName().equals(parameterClass.getCanonicalName())

println 'Are the two types equal? ' + superClass.equals(parameterClass)

// This fails with:

// org.gradle.internal.metaobject.AbstractDynamicObject$CustomMessageMissingMethodException: Could

// not find method registerTransform() for arguments [MyTransform@cac15ac] on object of type

// com.android.build.gradle.AppExtension.

android.registerTransform(new MyTransform())

Why is this occuring? How can it be dealt with?

The printlns suggest that the superclass of MyTransform is a different type from the first parameter to registerTransform(), but I don't understand how that could be. The names match, but somehow the types are not the same.

Thanks.

[Alex Waters]

When you do apply from: 'other.gradle' it does weird classloader things such that the two scripts have different classloaders (and thus even though it's the "same" class, it's not seen as the same to the JVM - a very irritating aspect of Gradle build scripts).

Can you put that same code at the end of the file instead? If that works then it's likely this.

I can't suggest a work-around unfortunately other than not using "apply from" (if you do discover a nice fix please post it)

[Malcolm Evershed]

To work-around, you can put the code in a buildSrc project: https://docs.gradle.org/3.3/userguide/organizing_build_logic.html#sec:build_sources