Unable to use Moshi Kotlin Reflect with JPMS

[MariusVolkhart]

We have a modularized (Java Platform Module System / JPMS / Jigsaw) application written in Kotlin. We build using Gradle and the Java Modules plugin.

We'd like to use Moshi Kotlin reflection, but are running into build-time errors.

error: the unnamed module reads package com.squareup.moshi from both com.squareup.moshi and com.squareup.moshi.kotlin
error: the unnamed module reads package com.squareup.moshi from both com.squareup.moshi and com.squareup.moshi.kotlin

error: module kotlin.stdlib.jdk7 reads package com.squareup.moshi from both com.squareup.moshi.kotlin and com.squareup.moshi
error: module kotlin.reflect reads package com.squareup.moshi from both com.squareup.moshi.kotlin and com.squareup.moshi
error: module kotlin.stdlib.jdk7 reads package com.squareup.moshi from both com.squareup.moshi.kotlin and com.squareup.moshi

error: module kotlin.stdlib reads package com.squareup.moshi from both com.squareup.moshi.kotlin and com.squareup.moshi
error: module kotlin.reflect reads package com.squareup.moshi from both com.squareup.moshi.kotlin and com.squareup.moshi

error: module kotlin.stdlib reads package com.squareup.moshi from both com.squareup.moshi.kotlin and com.squareup.moshi

error: module com.squareup.moshi reads package com.squareup.moshi from both com.squareup.moshi.kotlin and com.squareup.moshi
error: module com.squareup.moshi reads package com.squareup.moshi from both com.squareup.moshi.kotlin and com.squareup.moshi

error: module kotlin.stdlib.common reads package com.squareup.moshi from both com.squareup.moshi.kotlin and com.squareup.moshi
error: module annotations reads package com.squareup.moshi from both com.squareup.moshi.kotlin and com.squareup.moshi
error: module okio reads package com.squareup.moshi from both com.squareup.moshi.kotlin and com.squareup.moshi
error: module kotlin.stdlib.jdk8 reads package com.squareup.moshi from both com.squareup.moshi.kotlin and com.squareup.moshi
error: module kotlin.stdlib.common reads package com.squareup.moshi from both com.squareup.moshi.kotlin and com.squareup.moshi

error: module com.squareup.moshi.kotlin reads package com.squareup.moshi from both com.squareup.moshi and com.squareup.moshi.kotlin
error: module annotations reads package com.squareup.moshi from both com.squareup.moshi.kotlin and com.squareup.moshi

error: module okio reads package com.squareup.moshi from both com.squareup.moshi.kotlin and com.squareup.moshi

error: module kotlin.stdlib.jdk8 reads package com.squareup.moshi from both com.squareup.moshi.kotlin and com.squareup.moshi

moshi-modules/src/main/java/module-info.java:1: error: module example reads package com.squareup.moshi from both com.squareup.moshi.kotlin and com.squareup.moshi
error: module com.squareup.moshi.kotlin reads package com.squareup.moshi from both com.squareup.moshi and com.squareup.moshi.kotlin

Gradle: 6.5
Modular plugin: 1.7.0
Moshi: 1.9.3
Kotlin: 1.3.72
JVM: AdoptOpenJDK OpenJ9 (build 11.0.7+10)

Attached is a simple project that reproduces the problem.
moshi-modules.zip

[MariusVolkhart]

If I delete the old KotlinJsonAdapter and then install & use Moshi, the errors go away.

[ZacSweers]

The old KotlinJsonAdapter can't be deleted without a new major version, but it can be safely ignored if just excluding it is an option.

[MariusVolkhart]

@ZacSweers by excluding do you mean a Gradle exclusion? That could probably be made to work if the deprecated KotlinJsonAdapter was moved to a new artifact, something like com.squareup.moshi:moshi-kotlin-deprecated and then com.squareup.moshi:moshi-kotlin had a dependency on that.

However, in the current form, I haven't figured out a way to trick the compiler into allowing the JAR to be used.

I can't patch the moshi-kotlin JAR into the com.squareup.moshi module, because then 2 modules (com.squareup.moshi and com.squareup.moshi.reflect) export the same packages.

One option might be to do some additional shadowing/proguard step to remove the deprecated class, but that's still a pretty big step for a project that doesn't require that already.

Removing the automatic module name also doesn't work, because then you still have the unnamed module and the com.squareup.moshi modules exporting the com.squareup.moshi package.

[MariusVolkhart]

Here's a little sample project that just has a bare-bones gradle setup and basic moshi setup

jpms-moshi.zip

[ZacSweers]

If there's no way to exclude certain classes then you're out of luck until a new major release. You would be better off making a local build of Moshi with it removed and just package it directly into your project as a jar dependency.

[yogurtearl]

is the plan to remove KotlinJsonAdapter for 2.x?

[ZacSweers]

Not currently (old or new), but we could possibly look at removing the old one as an intentional breaking change