add nullable support in JSON converters

2 files changed, 10 insertions, 2 deletions

diff --git a/docs/release-notes.md b/docs/release-notes.md
index c04ac4e5..0678f6e1 100644
--- a/docs/release-notes.md
+++ b/docs/release-notes.md
@@ -3,7 +3,10 @@
 # Release notes
 ## Upcoming release
 * For players:
-  * Fixed crash loading mods if they have corrupted translation files.
+  * Fixed crash loading mods with corrupted translation files.
+
+* For mod authors:
+  * Improved SMAPI's crossplatform read/writing of `Color`, `Point`, `Rectangle`, and `Vector2` in JSON to support nullable fields too.
 
 ## 3.12.6
 Released 03 September 2021 for Stardew Valley 1.5.4 or later.
diff --git a/src/SMAPI.Toolkit/Serialization/Converters/SimpleReadOnlyConverter.cs b/src/SMAPI.Toolkit/Serialization/Converters/SimpleReadOnlyConverter.cs
index 549f0c18..ccc5158b 100644
--- a/src/SMAPI.Toolkit/Serialization/Converters/SimpleReadOnlyConverter.cs
+++ b/src/SMAPI.Toolkit/Serialization/Converters/SimpleReadOnlyConverter.cs
@@ -22,7 +22,7 @@ namespace StardewModdingAPI.Toolkit.Serialization.Converters
         /// <param name="objectType">The object type.</param>
         public override bool CanConvert(Type objectType)
         {
-            return objectType == typeof(T);
+            return objectType == typeof(T) || Nullable.GetUnderlyingType(objectType) == typeof(T);
         }
 
         /// <summary>Writes the JSON representation of the object.</summary>
@@ -44,10 +44,15 @@ namespace StardewModdingAPI.Toolkit.Serialization.Converters
             string path = reader.Path;
             switch (reader.TokenType)
             {
+                case JsonToken.Null when Nullable.GetUnderlyingType(objectType) != null:
+                    return null;
+
                 case JsonToken.StartObject:
                     return this.ReadObject(JObject.Load(reader), path);
+
                 case JsonToken.String:
                     return this.ReadString(JToken.Load(reader).Value<string>(), path);
+
                 default:
                     throw new SParseException($"Can't parse {typeof(T).Name} from {reader.TokenType} node (path: {reader.Path}).");
             }