Component used: Navigation
Version used: 1.0.0-alpha09
Devices/Android versions reproduced on: Pixel 3 XL (API 28)

Using the Navigation 1.0.0-alpha09 Safe Args plugin fails during Gradle sync with the following exception:

Caused by: kotlin.TypeCastException: null cannot be cast to non-null type org.gradle.api.resources.TextResource
at androidx.navigation.safeargs.gradle.SafeArgsPlugin.setApplicationId(SafeArgsPlugin.kt:87)
at androidx.navigation.safeargs.gradle.SafeArgsPlugin.access$setApplicationId(SafeArgsPlugin.kt:39)
at androidx.navigation.safeargs.gradle.SafeArgsPlugin$apply$1$task$1.execute(SafeArgsPlugin.kt:63)
at androidx.navigation.safeargs.gradle.SafeArgsPlugin$apply$1$task$1.execute(SafeArgsPlugin.kt:39)
at org.gradle.api.internal.tasks.DefaultTaskContainer.create(DefaultTaskContainer.java:334)
at androidx.navigation.safeargs.gradle.SafeArgsPlugin$apply$1.invoke(SafeArgsPlugin.kt:59)
at androidx.navigation.safeargs.gradle.SafeArgsPlugin$apply$1.invoke(SafeArgsPlugin.kt:39)
at androidx.navigation.safeargs.gradle.SafeArgsPluginKt$sam$org_gradle_api_Action$0.execute(SafeArgsPlugin.kt)

This appears to be a regression introduced by:

https://android-review.googlesource.com/845025

See the attached minimal sample project to reproduce. Downgrading navigation_version to 1.0.0-alpha08 or removing apply plugin: "androidx.navigation.safeargs" from the library module's build.gradle file "fixes" the issue.