Moshi: Platform kotlin.Pair<java.lang.String, java.lang.String> annotated [] requires explicit JsonAdapter to be registered

[robstoll]

Maybe I am doing something wrong but I think that should work out of the box. I get an IllegalArgumentException for the following:

val listPairStringType = Types.newParameterizedType(
    List::class.java,
    Types.newParameterizedType(Pair::class.java, String::class.java, String::class.java)
)
val listPairStringAdapter = moshi.adapter<List<Pair<String, String>>>(listPairStringType)

following the stack-trace:

Exception in thread "main" java.lang.IllegalArgumentException: Platform kotlin.Pair<java.lang.String, java.lang.String> annotated [] requires explicit JsonAdapter to be registered
        at com.squareup.moshi.ClassJsonAdapter$1.create(ClassJsonAdapter.java:51)
        at com.squareup.moshi.Moshi.adapter(Moshi.java:100)
        at com.squareup.moshi.Moshi.adapter(Moshi.java:58)
        at com.squareup.moshi.CollectionJsonAdapter.newArrayListAdapter(CollectionJsonAdapter.java:52)
        at com.squareup.moshi.CollectionJsonAdapter$1.create(CollectionJsonAdapter.java:36)
        at com.squareup.moshi.Moshi.adapter(Moshi.java:100)
        at com.squareup.moshi.Moshi.adapter(Moshi.java:58)

[NightlyNexus]

From the README

Moshi refuses to serialize platform types (java.*, javax.*, and android.*) without a user-provided type adapter. This is intended to prevent you from accidentally locking yourself to a specific JDK or Android release.

Use an adapter that uses only the public API for types you don't control (instead of using the built-in reflective adapter that relies on implemention details of a version of the type).

[robstoll]

Thanks for the quick reply. Maybe worth considering to add an adapter for Pair since it is so commonly used in Kotlin.

[swankjesse]

Should pairs be encoded like a pair:

["a", "b"]

Or like a data class:

{
  "first": "a",
  "second": "b"
}

I don't feel comfortable having Moshi make this choice for you.

[robstoll]

Fair enough, I am using ["a", "b"]. In case someone else wants the adapter:
https://github.com/loewenfels/dep-graph-releaser/blob/66c822830aa38ac6b4a2278dfe0020d551782bf0/dep-graph-releaser-serialization/src/main/kotlin/ch/loewenfels/depgraph/serialization/PairAdapterFactory.kt