IssueTracker

saveable has built-in support for Compose's MutableState, supporting this use case:

val state by saveable { mutableStateOf(...) }

It does this by providing an overloaded function that handles MutableState.value and serializes it when needed.

To help people migrate from saveable to saved, we want to support MutableState in our KotlinX serialization support.

While working on getMutableState, I experimented with this and created a naive KSerializer implementation to handle MutableState.

Here’s what it could look like:

private class StateSerializer<T : Any>(val valueSerializer: KSerializer<T>)

public inline fun <reified T : Any> stateSerializer(): KSerializer<MutableState<T>>

For serialization, we'd use (value as MutableState<T>).value + valueSerializer to serialize the content. Deserialization works in the opposite direction.

Here’s a usage example:

val state by saved(serializer = stateSerializer<Int>()) { mutableStateOf(1) }

However, calling this without the serializer would cause an exception.

Our variant should work like saveable: if T (the generic type in saved) is serializable, it should work without needing the serializer.

The goal is to find the best way to support MutableState in saved (using a KSerializer, overloads, or another method).

Related to b/378895070.