fix(proguard): fix gson proguard rules and clean up other rules (#383)

- Fix proguard rules for GSON to one recommended by the GSON repo (https://github.com/google/gson/blob/master/examples/android-proguard-example/proguard.cfg)
- Clean up other proguard files.

Author: jaeopt

android-sdk/build.gradle

@@ -29,6 +29,7 @@ android {
         versionName version_name
         testInstrumentationRunner 'androidx.test.runner.AndroidJUnitRunner'
         buildConfigField "String", "CLIENT_VERSION", "\"$version_name\""
+        // these rules will be merged to app's proguard rules
         consumerProguardFiles '../proguard-rules.txt'
     }
     testOptions {
@@ -37,7 +38,6 @@ android {
     buildTypes {
         release {
             minifyEnabled false
-            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
         }
         debug {
             testCoverageEnabled true

android-sdk/proguard-rules.pro

@@ -28,15 +28,13 @@ android {
         versionCode 1
         versionName version_name
         testInstrumentationRunner 'androidx.test.runner.AndroidJUnitRunner'
-        consumerProguardFiles '../proguard-rules.txt'
     }
     testOptions {
         unitTests.returnDefaultValues = true
     }
     buildTypes {
         release {
             minifyEnabled false
-            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
         }
         debug {
             testCoverageEnabled true

datafile-handler/build.gradle

@@ -28,15 +28,13 @@ android {
         versionCode 1
         versionName "1.0"
         testInstrumentationRunner 'androidx.test.runner.AndroidJUnitRunner'
-        consumerProguardFiles '../proguard-rules.txt'
     }
     testOptions {
         unitTests.returnDefaultValues = true
     }
     buildTypes {
         release {
             minifyEnabled false
-            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
         }
         debug {
             testCoverageEnabled true

datafile-handler/proguard-rules.pro

@@ -40,9 +40,6 @@
 -keep class com.optimizely.ab.bucketing.DecisionService { *; }
 -keep class com.optimizely.ab.Optimizely { *; }
 
-# Gson
--keepnames class com.google.gson.Gson
-
 # Safely ignore warnings about other libraries since we are using Gson
 -dontwarn com.fasterxml.jackson.**
 -dontwarn org.json.**
@@ -65,3 +62,32 @@
 -dontwarn com.google.gson.**
 -dontwarn com.optimizely.ab.config.parser.**
 
+# Gson (https://github.com/google/gson/blob/master/examples/android-proguard-example/proguard.cfg)
+##---------------Begin: proguard configuration for Gson  ----------
+# Gson uses generic type information stored in a class file when working with fields. Proguard
+# removes such information by default, so configure it to keep all of it.
+-keepattributes Signature
+
+# For using GSON @Expose annotation
+-keepattributes *Annotation*
+
+# Gson specific classes
+-dontwarn sun.misc.**
+
+# Prevent proguard from stripping interface information from TypeAdapter, TypeAdapterFactory,
+# JsonSerializer, JsonDeserializer instances (so they can be used in @JsonAdapter)
+-keep class * extends com.google.gson.TypeAdapter
+-keep class * implements com.google.gson.TypeAdapterFactory
+-keep class * implements com.google.gson.JsonSerializer
+-keep class * implements com.google.gson.JsonDeserializer
+
+# Prevent R8 from leaving Data object members always null
+-keepclassmembers,allowobfuscation class * {
+  @com.google.gson.annotations.SerializedName <fields>;
+}
+
+# Retain generic signatures of TypeToken and its subclasses with R8 version 3.0 and higher.
+-keep,allowobfuscation,allowshrinking class com.google.gson.reflect.TypeToken
+-keep,allowobfuscation,allowshrinking class * extends com.google.gson.reflect.TypeToken
+##---------------End: proguard configuration for Gson  ----------
+

event-handler/build.gradle

@@ -28,15 +28,13 @@ android {
         versionCode 1
         versionName "1.0"
         testInstrumentationRunner 'androidx.test.runner.AndroidJUnitRunner'
-        consumerProguardFiles '../proguard-rules.txt'
     }
     testOptions {
         unitTests.returnDefaultValues = true
     }
     buildTypes {
         release {
             minifyEnabled false
-            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
         }
         debug {
             testCoverageEnabled true

event-handler/proguard-rules.pro

@@ -50,10 +50,10 @@ dependencies {
     // implementation "com.optimizely.ab:android-sdk:1.0.0"
     implementation "androidx.appcompat:appcompat:1.2.0"
     implementation "com.google.android.material:material:1.2.1"
-    // EXAMPLE REPLACE noveogroup android-looger with slf4j-android logger
+    // EXAMPLE - replace noveogroup android-looger with slf4j-android logger
     // https://mvnrepository.com/artifact/org.slf4j/slf4j-android
     //implementation "org.slf4j:slf4j-android:1.7.25"
-    // EXAMPLE REPLACE gson json parsing with jackson-databind json parsing.
+    // EXAMPLE - replace gson with jackson-databind json parser
     implementation "com.fasterxml.jackson.core:jackson-databind:$jacksonversion"
 
     // required by API-16