IssueTracker

Jetifier is supposed to work on third-party libraries that do not yet support AndroidX. However, if a library has already been updated to support AndroidX, or if it is not using AndroidX/support libraries at all, then it is not necessary to run Jetifier to convert it, and doing so may even result in incorrect rewritten binaries.

Example failures:

(1) http://issuetracker.google.com/118658603#comment1
Execution failed for task ':app:kaptGenerateStubsDebugKotlin'.
> Could not resolve all files for configuration ':app:kapt'.
   > Failed to transform file 'butterknife-compiler-9.0.0-SNAPSHOT.jar' to match attributes {artifactType=processed-jar} using transform JetifyTransform
      > Failed to transform '...\.gradle\caches\modules-2\files-2.1\com.jakewharton\butterknife-compiler\9.0.0-SNAPSHOT\d5efd0795737d4523044335a7faa82b0e3d984c9\butterknife-compiler-9.0.0-SNAPSHOT.jar' using Jetifier.
Reason: The given artifact contains a string literal with a package reference 'android.support.v4.content' that cannot be safely rewritten. Libraries using reflection such as annotation processors need to be updated manually to add support for androidx.

(2) http://issuetracker.google.com/113224601#comment13
Execution failed for task ':app:kaptGenerateStubsDebugKotlin'.
> Could not resolve all files for configuration ':app:kapt'.
   > Failed to transform file 'jetifier-core-1.0.0-alpha10.jar' to match attributes {artifactType=processed-jar} using transform JetifyTransform
      > Failed to transform '/Users/nkotula/.gradle/caches/modules-2/files-2.1/com.android.tools.build.jetifier/jetifier-core/1.0.0-alpha10/9eb7027c383061de12f93aae7a22cbeb97832d2a/jetifier-core-1.0.0-alpha10.jar' using Jetifier. Reason: The given artifact contains a string literal with a package reference 'android/support/v4' that cannot be safely rewritten. Libraries using reflection such as annotation processors need to be updated manually to add support for androidx.

(In this example, Jetifier even tries to jetify itself!)

(3) http://issuetracker.google.com/113880420
Execution failed for task ':app:kaptGenerateStubsDebugKotlin'.
> Could not resolve all files for configuration ':app:kapt'.
   > Failed to transform file 'kotlin-compiler-embeddable-1.2.21.jar' to match attributes {artifactType=processed-jar} using transform JetifyTransform
      > Failed to transform '/root/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-compiler-embeddable/1.2.21/39456b64a42dc359e385697e2e93b5cba52e197f/kotlin-compiler-embeddable-1.2.21.jar' using Jetifier.
Reason: Malformed input or input contains unmappable characters: javaslang/?.class.

(In this example, kotlin-compiler-embeddable-1.2.21.jar does not need to be jetified but was jetified and then failed.)


We need a way to determine whether a third-party library should be jetified or not. There are a couple of approaches:
    1. The library adds some metadata stating that it is AndroidX-ready and therefore should not be jetified. (The Android Gradle plugin can also help to add this information automatically for libraries that are built using the AGP.)
    2. Jetifier automatically detects the presence of AndroidX (e.g., import statements and strings containing references to AndroidX), and if AndroidX is present, assumes that the library is AndroidX-ready and skips converting it.
    3. The users need to specify a blacklist of libraries that should not be jetified.

We'll need to weigh the pros and cons of these approaches and select the best one (or a combination of them).