IssueTracker

I have not tried to create a project, but the way -if rules are evaluated is that if the condition public class ** extends androidx.fragment.app.Fragment holds (that is at least one class extends androidx.fragment.app.Fragment then the subsequent -keep rule is activated, so if at least one class extends androidx.fragment.app.Fragment this keep rule is activated:

-keep public class ** extends androidx.fragment.app.Fragment {
    public <init>();
}

Causing all classes in the app extending androidx.fragment.app.Fragment to be kept. The -if rule captures <n> are used to parameterize the subsequent keep rule with what was matched by the condition. Each wildcard in the condition will be given a capture number (starting from 1) and they can then be used in the subsequent rule. So if the keep rule is:

-keep public class <1> {
    public <init>();
}

Then if e.g. class com.example.app.MyFragment extends androidx.fragment.app.Fragment, then the following rule will be activated:

-keep public class com.example.app.MyFragment {
    public <init>();
}

Which I assume is the expected behaviour.

It might be for most apps all classes which extend androidx.fragment.app.Fragment ends up being part of the program, so the end result ends up being the same, but I still think that the rule should be precise and only keep what the condition matches.

We've fixed the ProGuard rules and it'll be available in the upcoming Fragment 1.3.0-alpha01 (and if we do a Fragment 1.2.3, it'll also be a part of that).

Maybe this is intentional, but I updated my project to androidx fragments 1.2.3 (from 1.2.2), and now necessary fragments ("MyFragment" below) that used to be kept are now being stripped by R8. The fragment in question is referenced in a layout that is set using setContentView() on an activity.

   <androidx.fragment.app.FragmentContainerView
         android:id="@+id/fragment_id"
         android:name="com.mycompany.MyFragment"
         android:layout_width="match_parent"
         android:layout_height="match_parent" />

AGP 3.6.1. Not sure how I'm supposed to keep it now. It has normal default constructor and has androidx.fragment.Fragment in the superclass hierarchy.

Re #7 - that's unrelated and expected when using AGP 3.6.1 as per the Fragment 1.2.0 release notes Known Issues - see b/142601969 for the actual fix.

The only reason that it "worked" in Fragment 1.2.2 was because all Fragments were being kept if even one Fragment was being kept (which is what this bug fixed).

What's the reason for having Proguard rules included with the Fragment library in the first place?

I'm asking because right now, this rule is actually preventing me from obfuscating, shrinking and optimizing my fragments for reasons I don't understand. One reason I could think of is reflection. Instead, is it possible to completely remove them and suggest developers to add these rules themselves?

Re #9 - please star b/151605338 for obfuscation. Fragment 1.2.3 (with this fix) already allows shrinking and the removal of unused Fragment classes.