Enable obfuscation.

app/build.gradle

@@ -103,14 +103,11 @@ android {
 
     buildTypes {
         debug {
-            minifyEnabled false
-            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
-            testProguardFiles 'test-proguard-rules.pro'
         }
         release {
-            minifyEnabled true
-            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
-            testProguardFiles 'test-proguard-rules.pro'
+            optimization {
+                enable = true
+            }
         }
     }
 

app/src/main/keepRules/custom-rules.keep

@@ -0,0 +1,16 @@
+
+# Callbacks for Reading Challenge widget
+-keep class * implements androidx.glance.appwidget.action.ActionCallback { public <init>(); }
+
+# Accessed via reflection in OnThisDayGameArchiveCalendarHelper
+-keepclassmembers class com.google.android.material.datepicker.MaterialDatePicker {
+    com.google.android.material.datepicker.MaterialCalendar calendar;
+}
+
+# Class names are used as analytics values
+-keepnames class * extends org.wikipedia.feed.model.Card
+-keepnames class * extends androidx.fragment.app.Fragment
+-keepnames class * extends java.lang.Throwable
+
+# Parcelables can outlive an app update in widget options and PendingIntents
+-keepnames class * implements android.os.Parcelable