Is "@Keep support annotation" rule in proguard-android-optimize.txt still applicable when using AndroidX?

Question

It is common to apply proguard-android-optimize.txt as proguard file.

proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-project.txt'

However, when I went through the content of proguard-android-optimize.txt

...

-keepclassmembers class **.R$* {
    public static <fields>;
}

# The support library contains references to newer platform versions.
# Don't warn about those in case this app is linking against an older
# platform version.  We know about them, and they are safe.
-dontwarn android.support.**

# Understand the @Keep support annotation.
-keep class android.support.annotation.Keep

-keep @android.support.annotation.Keep class * {*;}

-keepclasseswithmembers class * {
    @android.support.annotation.Keep <methods>;
}

-keepclasseswithmembers class * {
    @android.support.annotation.Keep <fields>;
}

-keepclasseswithmembers class * {
    @android.support.annotation.Keep <init>(...);
}

I was wondering, if such rule still applicable, if we were using AndroidX instead of support library? Should we add the following rules explicitly in our project proguard-project.txt?

# Understand the @Keep support annotation.
-keep class androidx.annotation.Keep

-keep @androidx.annotation.Keep class * {*;}

-keepclasseswithmembers class * {
    @androidx.annotation.Keep <methods>;
}

-keepclasseswithmembers class * {
    @androidx.annotation.Keep <fields>;
}

-keepclasseswithmembers class * {
    @androidx.annotation.Keep <init>(...);
}

Answer 1

I just checked it and annotating classes with the androidx.annotation.Keep keeps them. No additional configuration required.

Answer 2

If you don't use proguard-android-optimize.txt or proguard-android.txt, you should add

-keep class androidx.annotation.Keep {*;}

Or, your @Keep will turn to @a

If you use proguard-android-optimize.txt or proguard-android.txt, it still work.

Hope it will work for you.

Answer 3

The androidx.annotation:annotation:x.x.z has its own proguard declaration:

-keep,allowobfuscation @interface androidx.annotation.Keep
-keep @androidx.annotation.Keep class * {*;}

-keepclasseswithmembers class * {
    @androidx.annotation.Keep <methods>;
}

-keepclasseswithmembers class * {
    @androidx.annotation.Keep <fields>;
}

-keepclasseswithmembers class * {
    @androidx.annotation.Keep <init>(...);
}

-keepclassmembers,allowobfuscation class * {
    @androidx.annotation.DoNotInline <methods>;
}

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