Ensure that SettingsEncoder is correctly reset to initial state after…

… finishing an encoding, in case of reuse such as with delegates. Fixes #217
russhwolf · Nov 26, 2024 · d656c58 · d656c58
1 parent 0f9a6de
commit d656c58
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 - Update to Kotlin 2.0.21, Gradle 8.10, and Android Gradle Plugin 8.5.2
 - Add `wasmWasi` support to `multiplatform-settings-coroutines` and `multiplatform-settings-serialization`.
+- Fix an issue in `multiplatform-settings-serialization` where delegates might return wrong values or crash (#217).
 
 ## v1.2.0 *(2024-09-01)* ##
 

diff --git a/multiplatform-settings-serialization/src/commonMain/kotlin/SerializationInternals.kt b/multiplatform-settings-serialization/src/commonMain/kotlin/SerializationInternals.kt
@@ -31,7 +31,7 @@ import kotlinx.serialization.modules.SerializersModule
 @ExperimentalSerializationApi
 internal class SettingsEncoder(
     private val settings: Settings,
-    key: String,
+    private val key: String,
     public override val serializersModule: SerializersModule
 ) : AbstractEncoder() {
 
@@ -60,6 +60,10 @@ internal class SettingsEncoder(
     public override fun endStructure(descriptor: SerialDescriptor) {
         depth--
         keyStack.removeLast()
+        if (keyStack.isEmpty()) {
+            // We've reached the end of everything, so reset for potential encoder reuse
+            keyStack.add(key)
+        }
     }
 
     public override fun beginCollection(descriptor: SerialDescriptor, collectionSize: Int): CompositeEncoder {

diff --git a/multiplatform-settings-serialization/src/commonTest/kotlin/SettingsSerializationTest.kt b/multiplatform-settings-serialization/src/commonTest/kotlin/SettingsSerializationTest.kt
@@ -21,6 +21,7 @@ import com.russhwolf.settings.MapSettings
 import com.russhwolf.settings.Settings
 import com.russhwolf.settings.contains
 import kotlinx.serialization.ExperimentalSerializationApi
+import kotlinx.serialization.SerialName
 import kotlinx.serialization.Serializable
 import kotlinx.serialization.SerializationException
 import kotlinx.serialization.builtins.ListSerializer
@@ -1023,6 +1024,46 @@ class SettingsSerializationTest {
         preferences.list = list
         assertEquals(expected = list, actual = preferences.list)
     }
+
+    @Test
+    fun issue_217() {
+        val settings = MapSettings()
+
+        @Serializable
+        data class MyItemDto(
+            @SerialName("name")
+            val name: String,
+            @SerialName("id")
+            val id: String,
+        )
+
+        var myItems: List<MyItemDto> by settings.serializedValue(
+            ListSerializer(MyItemDto.serializer()),
+            "MY_ITEMS",
+            emptyList(),
+        )
+
+        myItems = emptyList()
+        assertEquals(emptyList(), myItems)
+        myItems = listOf(
+            MyItemDto(
+                name = "Name",
+                id = "Id",
+            )
+        )
+        assertEquals(
+            listOf(
+                MyItemDto(
+                    name = "Name",
+                    id = "Id",
+                )
+            ), myItems
+        )
+
+        // Should not crash
+        myItems = emptyList()
+        myItems = emptyList()
+    }
 }
 
 @Serializable