serializedValue does not work with ListSerializer(String.serializer())

[vanniktech]

The following test fails on the last assertEquals:

class SomeTest {
  @Test fun foo() {
    val preferences = Preferences(MapSettings())
    assertEquals(expected = emptyList(), actual = preferences.list)

    val list = listOf("Hello", "World")
    preferences.list = list
    assertEquals(expected = list, actual = preferences.list)
  }

  class Preferences(settings: Settings) {
    @OptIn(ExperimentalSerializationApi::class, ExperimentalSettingsApi::class)
    var list by settings.serializedValue(
      serializer = ListSerializer(String.serializer()),
      key = "something",
      defaultValue = emptyList(),
    )
  }
}

I would have expected to have a properly saved list but instead it's empty.

Public reproducer: https://github.com/vanniktech/playground/pull/116

However, nullableSerializedValue seems to work. You can check yourself by applying the following patch file:

diff --git a/kmp/src/commonTest/kotlin/com/vanniktech/playground/kmp/SomeTest.kt b/kmp/src/commonTest/kotlin/com/vanniktech/playground/kmp/SomeTest.kt
index 308463e..3372a64 100644
--- a/kmp/src/commonTest/kotlin/com/vanniktech/playground/kmp/SomeTest.kt
+++ b/kmp/src/commonTest/kotlin/com/vanniktech/playground/kmp/SomeTest.kt
@@ -3,7 +3,7 @@ package com.vanniktech.playground.kmp
 import com.russhwolf.settings.ExperimentalSettingsApi
 import com.russhwolf.settings.MapSettings
 import com.russhwolf.settings.Settings
-import com.russhwolf.settings.serialization.serializedValue
+import com.russhwolf.settings.serialization.nullableSerializedValue
 import kotlinx.serialization.ExperimentalSerializationApi
 import kotlinx.serialization.builtins.ListSerializer
 import kotlinx.serialization.builtins.serializer
@@ -13,7 +13,7 @@ import kotlin.test.assertEquals
 class SomeTest {
   @Test fun foo() {
     val preferences = Preferences(MapSettings())
-    assertEquals(expected = emptyList(), actual = preferences.list)
+    assertEquals(expected = null, actual = preferences.list)

     val list = listOf("Hello", "World")
     preferences.list = list
@@ -22,10 +22,9 @@ class SomeTest {

   class Preferences(settings: Settings) {
     @OptIn(ExperimentalSerializationApi::class, ExperimentalSettingsApi::class)
-    var list by settings.serializedValue(
+    var list by settings.nullableSerializedValue(
       serializer = ListSerializer(String.serializer()),
       key = "something",
-      defaultValue = emptyList(),
     )
   }
 }

[russhwolf]

Thanks for the reproducer! This looks like it's probably the same issue as #160.

[vanniktech]

nullableSerializedValue does work when using MapSettings(); however on my Android App nullableSerializedValue didn't work correctly with the Shared Preferences Settings implementation.

[russhwolf]

Take a look at the 1.1 branch. I think I have this fixed but I'm not clear on the shared prefs difference you mentioned. I do expect possible behavior variations in the old implementation between the first time you deserialize and subsequent times, so that might account for what you saw, but I'm not certain.

[russhwolf]

The issues I can reproduce are fixed in 1.1.0. Let me know if there's still anything that isn't working for you.