Fix for "Kotlin sourceDir isn't take into account"

[StefMa]

Closes #702

Description:

An detailed explanation why can be read in #702

I also had the upgrade the AGP to version 7.0.0 because the 4.1.0 doesn't know the kotlin property 😁
7.0.0 is the first version that supports hit.
Yes, this would be an potential breaking change.
But please take a look at the release dates for those plugins:
https://maven.google.com/web/index.html?q=tools.bui#com.android.tools.build:gradle:4.1.0
-> Release at 10th December 2020

https://maven.google.com/web/index.html?q=tools.bui#com.android.tools.build:gradle:7.0.0
-> Release at 28th July 2021

As the Android community is normaly quite good in upgrading the core plugin to develop, I guess we are fine 😁

Changes:

• Upgrade Android Gradle Plugin from 4.1.0 to 7.0.0
• Use kotlin sourceSet instead of java sourceSet

How to test:

1. Change the version in /plugin/VERSION_CURRENT.txt to something else e.g. "testKotlinSourceSet"

cd plugin 
./gradlew publishToMavenLocal

3. Include the mavenLocal() repository (to find that version)
4. Replace the current ktlint-plugin version (in your project) with the one you change din the /plugin/VERSION_CURRENT.txt

[wakingrufus]

To be clear about what this breaks, it would mean that we now require AGP >=7.0 and Gradle >= 7.0?

I am ok with this, but I would like to queue up some related maintenance work around dropping Gradle 6 support so we can merge them all around the same time and release it as 16.0

[StefMa]

Yes, that's correct.
AGP 7.0 has to be used and this would required Gradle 7.0 (as also documented here https://developer.android.com/build/releases/gradle-plugin#expandable-1)

Sure, do the maintaince work and come back as you're finish with that ☺.

You can also let me when I can help with that somewhere.

[StefMa]

@wakingrufus did you had the time to look into this yet?

[wakingrufus]

@wakingrufus did you had the time to look into this yet?

Not yet. I need to finish up #708 first

[StefMa]

It's going to be happen 🤘 🙃

[JLLeitschuh]

Yes, this would be an potential breaking change.

Do we want to accept this API breaking change? Does this break our guarantee of android plugin support range?

Do we currently have unit tests that cover the range of android plugins we want to ensure we support? If we don't we should.

[StefMa]

I just saw that we set the AGP only as a compileOnly dependency

ktlint-gradle/plugin/build.gradle.kts

Line 135 in a826dcd

compileOnly(libs.android.gradle.plugin)

With that we can also workaround the breaking change by adding a try-catch 🤔

val androidSourceSet = try {
  sourceSet.kotlin as DefaultAndroidSourceDirectorySet
} catch(_: java.lang.NoSuchMethodError) {
  java as DefaultAndroidSourceDirectorySet
} 

Update

Unfortunately this is not really working as the signature of the CommonExtension also changed :/

[Goooler]

Seems this could be closed for now, handled by #733.