Add a Saver parameter to SaveableMutableStateSource (#213)

README.md

@@ -200,6 +200,26 @@ internal class MyFeatureDialogSource : MutableStateSource<MyFeatureDialogState>
 }
 ```
 
+### SaveableMutableStateSource
+
+`SaveableMutableStateSource` is the same as `MutableStateSource` except it wraps its internal `State` in a
+`rememberSaveable` call.
+
+
+```kotlin
+internal class MyCounterSource : SaveableMutableStateSource<Int> {
+  override val initial = 0
+
+  fun reset() {
+    update(0)
+  }
+
+  fun increment() {
+    update(value + 1)
+  }
+}
+```
+
 ### DerivedStateSource
 
 `DerivedStateSource` is similar to `MutableStateSource`, but encapsulates the content of a `derivedStateOf` call:

vice-sources/src/commonMain/kotlin/com/eygraber/vice/sources/SaveableMutableStateSource.kt

@@ -3,12 +3,15 @@ package com.eygraber.vice.sources
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.State
 import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.saveable.Saver
 import androidx.compose.runtime.saveable.rememberSaveable
 import androidx.compose.runtime.snapshotFlow
 import com.eygraber.vice.ViceSource
 import kotlinx.coroutines.flow.Flow
 
-public abstract class SaveableMutableStateSource<T> : ViceSource<T>, State<T> {
+public abstract class SaveableMutableStateSource<T : Any>(
+  private val saver: Saver<T, out Any>? = null,
+) : ViceSource<T>, State<T> {
   private val state by lazy {
     mutableStateOf(initial)
   }
@@ -24,5 +27,8 @@ public abstract class SaveableMutableStateSource<T> : ViceSource<T>, State<T> {
   }
 
   @Composable
-  override fun currentState(): T = rememberSaveable { state }.value
+  override fun currentState(): T = when(saver) {
+    null -> rememberSaveable { state }.value
+    else -> rememberSaveable(stateSaver = saver) { state }.value
+  }
 }