Sample reproduction project for issues with warnings using kotlin experimental apis

Step 1 - No annotations or languageSettings gradle configuration

• Use an experimental api in a test class (MyTestApplicaton) (ok) and in an app class (MyApplication) (not ok)
  • Important: this api should be on an overridden function. In this example, it's on a class extetnding Application and on the overridden onCreate()

    override fun onCreate() {
        super.onCreate()
        TimeSource.Monotonic.markNow()
    }

• Build the app and test: ./gradlew clean assembleDebug testDebugUnitTest.
• Gradle outputs these errors for MyApplication and aborts the build:

e: /Users/calvarez/dev/projects/KotlinExperimentalAnnotations/app/src/main/java/ca/rmen/kotlinexperimentalannotations/MyApplication.kt: (11, 9): This declaration is experimental and its usage must be marked with '@kotlin.time.ExperimentalTime' or '@OptIn(kotlin.time.ExperimentalTime::class)'
e: /Users/calvarez/dev/projects/KotlinExperimentalAnnotations/app/src/main/java/ca/rmen/kotlinexperimentalannotations/MyApplication.kt: (11, 30): This declaration is experimental and its usage must be marked with '@kotlin.time.ExperimentalTime' or '@OptIn(kotlin.time.ExperimentalTime::class)'

• Android Studio Arctic Fox displays red compilation errors with this message, in both classes:

This declaration is experimental and its usage must be marked with '@kotlin.time.ExperimentalTime' or '@OptIn(kotlin.time.ExperimentalTime::class)'

Step 2 - Add OptIn annotation

• Add this annotation to the overriden onCreate function in both MyApplication and MyTestApplication:

  @OptIn(ExperimentalTime::class)
  override fun onCreate() {
      super.onCreate()
      TimeSource.Monotonic.markNow()
  }

• Build the app and test: ./gradlew clean assembleDebug testDebugUnitTest.
• Gradle outputs these warnings:

> Task :app:compileDebugKotlin
w: /Users/calvarez/dev/projects/KotlinExperimentalAnnotations/app/src/main/java/ca/rmen/kotlinexperimentalannotations/MyApplication.kt: (8, 6): This class can only be used with the compiler argument '-opt-in=kotlin.RequiresOptIn'

> Task :app:compileDebugUnitTestKotlin
w: /Users/calvarez/dev/projects/KotlinExperimentalAnnotations/app/src/test/java/ca/rmen/kotlinexperimentalannotations/MyTestApplication.kt: (7, 6): This class can only be used with the compiler argument '-opt-in=kotlin.RequiresOptIn'

• Android Studio Arctic Fox displays warnings with this message, in both classes:

This class can only be used with the compiler argument '-Xopt-in=kotlin.RequiresOptIn'

Step 3 - Add languageSettings configuration in build.gradle

Add the following gradle configuration to allow OptIn only for tests:

kotlin {
    sourceSets {
        test {
            languageSettings {
                optIn("kotlin.RequiresOptIn")
            }
        }
        debugUnitTest {
            languageSettings {
                optIn("kotlin.RequiresOptIn")
            }
        }
        releaseUnitTest {
            languageSettings {
                optIn("kotlin.RequiresOptIn")
            }
        }
    }
}

• Build the app and test: ./gradlew clean assembleDebug testDebugUnitTest.
• ✅Gradle outputs a warning, only for MyApplication. This is the desired behavior:

w: /Users/calvarez/dev/projects/KotlinExperimentalAnnotations/app/src/main/java/ca/rmen/kotlinexperimentalannotations/MyApplication.kt: (8, 6): This class can only be used with the compiler argument '-opt-in=kotlin.RequiresOptIn'

• Android Studio Arctic Fox displays warnings:
  • ✅For the app class: this is expected
  • ❌For the test class: this is unexpected. It's not taking into account our gradle conf
  • The kotlin plugin is: 203-1.5.31-release-550-AS7717.8
  • An update for the kotlin plugin is available: 203-1.6.0-release-798-AS7717.8
• Android Studio Bumblebee 2020.1.1 Beta 3 has the same behavior. It displays warnings:
  • ✅For the app class: this is expected
  • ❌For the test class: this is unexpected. It's not taking into account our gradle conf
  • The kotlin plugin is: 211-1.5.30-release-408-AS7442.40
  • An update for the kotlin plugin is available: 211-1.6.0-release-798-AS7442.40
• Android Studio Chipmunk 2021.2.1 Canary 5 has the same behavior. It displays warnings:
  • ✅For the app class: this is expected
  • ❌For the test class: this is unexpected. It's not taking into account our gradle conf
  • The kotlin plugin is: 212-1.5.31-release-556-AS4638.7
  • No kotlin plugin update is proposed

The warnings displayed in Android Studio are on the OptIn annotation:

This class can only be used with the compiler argument '-Xopt-in=kotlin.RequiresOptIn'

Step 4 - Update the Android Studio kotlin plugin

Android Studio Arctic Fox:

• In Android Studio, update the kotlin plugin to 203-1.6.0-release-798-AS7717.8
• Restart the IDE
• kotlin plugin 203-1.6.0-release-798-AS7717.8 is installed
• We have the same behavior: We see warnings:
  • ✅For the app class: this is expected
  • ❌For the test class: this is unexpected. It's not taking into account our gradle conf

Android Studio Bumblebee:

• In Android Studio, update the kotlin plugin to 211-1.6.0-release-798-AS7442.40
• Restart the IDE
• Kotlin plugin 211-1.6.0-release-798-AS7442.40 is installed
• We have the same behavior: We see warnings:
  • ✅For the app class: this is expected
  • ❌For the test class: this is unexpected. It's not taking into account our gradle conf