Moshi KotlinJsonAdapterFactory cannot parse Json after enabled minify

Question

I have developed an Android app, using Moshi as one of its dependencies.

Today I want to enable minify for this project. So I set minifyEnabled true in my build.gradle.

After that, I found that all responses from server become null.

First of all, I am using Retrofit2 to call APIs. The JSON body in Response.body() is not null and have correct values.

The response body is as below (simplified):

{"status":"success","data":{"user": "I am a user"}}

And I am using the code below to convert it to my own object:

val someResponse = Moshi.Builder().add(KotlinJsonAdapterFactory()).build().adapter(SomeResponse::class.java).fromJson(theJsonString)

While the code for SomeResponse:

class SomeResponse {
    @Json(name="status")
    var status: String? = null

    @Json(name="data")
    var data: User? = null
}

And then I simply use Log.i("Moshi", "${someResponse.status}" to see the value, and the result is null.

I have already included the proguard rules specified in the README section of Moshi Github, which is this one and this one.

Why and how do I solve this?

For reference, below is my full proguard-rules.pro:

# Add project specific ProGuard rules here.
# You can control the set of applied configuration files using the
# proguardFiles setting in build.gradle.
#
# For more details, see
#   http://developer.android.com/guide/developing/tools/proguard.html

# If your project uses WebView with JS, uncomment the following
# and specify the fully qualified class name to the JavaScript interface
# class:
-keepclassmembers class fqcn.of.javascript.interface.for.webview {
   public *;
}

# Uncomment this to preserve the line number information for
# debugging stack traces.
-keepattributes SourceFile,LineNumberTable, *Annotation*

# If you keep the line number information, uncomment this to
# hide the original source file name.
#-renamesourcefileattribute SourceFile


#Crashlytics: https://docs.fabric.io/android/crashlytics/dex-and-proguard.html
-keepattributes *Annotation*
-keep public class * extends java.lang.Exception


#https://stackoverflow.com/questions/36816521/is-the-format-of-the-data-held-in-kotlin-metadata-documented-anywhere
-dontwarn kotlin.**
-dontwarn kotlin.reflect.jvm.internal.**
-keep class kotlin.reflect.jvm.internal.** { *; }
-keep class kotlin.Metadata { *; }
-keepclassmembers public class com.example.app.** {
    public synthetic <methods>;
}
-keepclassmembers class kotlin.Metadata {
    public <methods>;
}
-keepclassmembers class **$WhenMappings {
    <fields>;
}
-keep class kotlin.reflect.jvm.internal.impl.builtins.BuiltInsLoaderImpl

#All models
-keep class com.example.app.models.**

#######Retrofit#######
#https://github.com/square/retrofit/blob/master/retrofit/src/main/resources/META-INF/proguard/retrofit2.pro
# Retrofit does reflection on generic parameters. InnerClasses is required to use Signature and
# EnclosingMethod is required to use InnerClasses.
-keepattributes Signature, InnerClasses, EnclosingMethod

# Retrofit does reflection on method and parameter annotations.
-keepattributes RuntimeVisibleAnnotations, RuntimeVisibleParameterAnnotations

# Retain service method parameters when optimizing.
-keepclassmembers,allowshrinking,allowobfuscation interface * {
    @retrofit2.http.* <methods>;
}

# Ignore annotation used for build tooling.
-dontwarn org.codehaus.mojo.animal_sniffer.IgnoreJRERequirement

# Ignore JSR 305 annotations for embedding nullability information.
-dontwarn javax.annotation.**

# Guarded by a NoClassDefFoundError try/catch and only used when on the classpath.
-dontwarn kotlin.Unit

# Top-level functions that can only be used by Kotlin.
-dontwarn retrofit2.KotlinExtensions

# With R8 full mode, it sees no subtypes of Retrofit interfaces since they are created with a Proxy
# and replaces all potential values with null. Explicitly keeping the interfaces prevents this.
-if interface * { @retrofit2.http.* <methods>; }
-keep,allowobfuscation interface <1>



#######OkHttp3######
#https://github.com/square/okhttp/blob/master/okhttp/src/main/resources/META-INF/proguard/okhttp3.pro
# JSR 305 annotations are for embedding nullability information.
-dontwarn javax.annotation.**

# A resource is loaded with a relative path so the package of this class must be preserved.
-keepnames class okhttp3.internal.publicsuffix.PublicSuffixDatabase

# Animal Sniffer compileOnly dependency to ensure APIs are compatible with older versions of Java.
-dontwarn org.codehaus.mojo.animal_sniffer.*

# OkHttp platform used only on JVM and when Conscrypt dependency is available.
-dontwarn okhttp3.internal.platform.ConscryptPlatform




######Okio######
#https://github.com/square/okio/blob/master/okio/src/jvmMain/resources/META-INF/proguard/okio.pro
# Animal Sniffer compileOnly dependency to ensure APIs are compatible with older versions of Java.
-dontwarn org.codehaus.mojo.animal_sniffer.*





####Moshi####
#https://github.com/square/moshi/blob/master/moshi/src/main/resources/META-INF/proguard/moshi.pro
#https://github.com/square/moshi/blob/master/kotlin/reflect/src/main/resources/META-INF/proguard/moshi-kotlin.pro
# JSR 305 annotations are for embedding nullability information.
-dontwarn javax.annotation.**

-keepclasseswithmembers class * {
    @com.squareup.moshi.* <methods>;
}

-keep @com.squareup.moshi.JsonQualifier interface *

# Enum field names are used by the integrated EnumJsonAdapter.
# Annotate enums with @JsonClass(generateAdapter = false) to use them with Moshi.
-keepclassmembers @com.squareup.moshi.JsonClass class * extends java.lang.Enum {
    <fields>;
}

# The name of @JsonClass types is used to look up the generated adapter.
-keepnames @com.squareup.moshi.JsonClass class *

# Retain generated JsonAdapters if annotated type is retained.
-if @com.squareup.moshi.JsonClass class *
-keep class <1>JsonAdapter {
    <init>(...);
    <fields>;
}
-if @com.squareup.moshi.JsonClass class **$*
-keep class <1>_<2>JsonAdapter {
    <init>(...);
    <fields>;
}
-if @com.squareup.moshi.JsonClass class **$*$*
-keep class <1>_<2>_<3>JsonAdapter {
    <init>(...);
    <fields>;
}
-if @com.squareup.moshi.JsonClass class **$*$*$*
-keep class <1>_<2>_<3>_<4>JsonAdapter {
    <init>(...);
    <fields>;
}
-if @com.squareup.moshi.JsonClass class **$*$*$*$*
-keep class <1>_<2>_<3>_<4>_<5>JsonAdapter {
    <init>(...);
    <fields>;
}
-if @com.squareup.moshi.JsonClass class **$*$*$*$*$*
-keep class <1>_<2>_<3>_<4>_<5>_<6>JsonAdapter {
    <init>(...);
    <fields>;
}
-keep class kotlin.reflect.jvm.internal.impl.builtins.BuiltInsLoaderImpl

-keepclassmembers class kotlin.Metadata {
    public <methods>;
}






####Mp4 Marser####
-keep class com.coremedia.iso.** {*;}
-keep class com.googlecode.mp4parser.** {*;}
-keep class com.mp4parser.** {*;}

-dontwarn com.coremedia.**
-dontwarn com.googlecode.mp4parser.**



####Picasso#####
#https://github.com/square/picasso/blob/master/picasso/consumer-proguard-rules.txt
# Platform calls Class.forName on types which do not exist on Android to determine platform.
-dontnote okhttp3.internal.Platform
# java.nio.file.* usage which cannot be used at runtime. Animal sniffer annotation.
-dontwarn okio.Okio
# JDK 7-only method which is @hide on Android. Animal sniffer annotation.
-dontwarn okio.DeflaterSink



#Ignore all other 3rd party libraries for now as we don't really care about the size but more about code obfuscation.
-keep class de.hdodenhof.**
-keep class io.github.luizgrp.sectionedrecyclerviewadapter.**
-keep class q.rorbin.badgeview.**
-keep class com.theartofdev.edmodo.**
-keep class me.relex
-keep class com.tbruyelle.rxpermissions2.**
-keep class com.github.pwittchen.reactivenetwork.**
-keep class com.minimize.android.rxrecycleradapter.**
-keep class at.blogc.android.**
-keep class com.yarolegovich.**
-keep class cn.trinea.android.view.autoscrollviewpager.**
-keep class com.apkfuns.logutils.**

Answer 1

The only solution worked for me is mentioned in the comment by @JeganBabu

i.e. Changing @Json(name="field_name") into @field:Json(name="field_name").

Probably the reason is the annotation is not applied to the converted Java code if field: was not added. Pretty odd.

For your reference: (Moshi in kotlin) @Json vs @field:Json

Answer 2

You can also use the Moshi "codegen" annotation processor.

Add the dependency:

kapt "com.squareup.moshi:moshi-kotlin-codegen:1.9.2"

Then annotate your models with @JsonClass:

@JsonClass(generateAdapter = true)
data class MyModel(...)

You also need to annotate any enum classes used by models, but they don't need an adapter:

@JsonClass(generateAdapter = false)
enum class MyEnumClass { ... }

The previously mentioned Moshi Proguard rules from here and here are also required.