Added JsonTypeSafeWrapper and JsonTypeSafeGenericDataHolder

CHANGELOG.md

@@ -38,6 +38,7 @@ Fixes
 ### MLEM.Data
 Additions
 - Allow RuntimeTexturePacker to automatically dispose submitted textures when packing
+- Added JsonTypeSafeWrapper and JsonTypeSafeGenericDataHolder
 
 Improvements
 - Use TitleContainer for opening streams where possible

MLEM.Data/Json/JsonTypeSafeGenericDataHolder.cs

@@ -0,0 +1,45 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.Serialization;
+using MLEM.Misc;
+using Newtonsoft.Json;
+
+namespace MLEM.Data.Json {
+    /// <summary>
+    /// An <see cref="IGenericDataHolder"/> represents an object that can hold generic key-value based data.
+    /// This class uses <see cref="JsonTypeSafeWrapper"/> for each object stored to ensure that objects with a custom <see cref="JsonConverter"/> get deserialized as an instance of their original type if <see cref="JsonSerializer.TypeNameHandling"/> is not set to <see cref="TypeNameHandling.None"/>.
+    /// </summary>
+    [DataContract]
+    public class JsonTypeSafeGenericDataHolder : IGenericDataHolder {
+
+        [DataMember(EmitDefaultValue = false)]
+        private Dictionary<string, JsonTypeSafeWrapper> data;
+
+        /// <inheritdoc />
+        public void SetData<T>(string key, T data) {
+            if (EqualityComparer<T>.Default.Equals(data, default)) {
+                if (this.data != null)
+                    this.data.Remove(key);
+            } else {
+                if (this.data == null)
+                    this.data = new Dictionary<string, JsonTypeSafeWrapper>();
+                this.data[key] = new JsonTypeSafeWrapper<T>(data);
+            }
+        }
+
+        /// <inheritdoc />
+        public T GetData<T>(string key) {
+            if (this.data != null && this.data.TryGetValue(key, out var val))
+                return (T) val.Value;
+            return default;
+        }
+
+        /// <inheritdoc />
+        public IEnumerable<string> GetDataKeys() {
+            if (this.data == null)
+                return Array.Empty<string>();
+            return this.data.Keys;
+        }
+
+    }
+}

MLEM.Data/Json/JsonTypeSafeWrapper.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.Serialization;
+using Newtonsoft.Json;
+
+namespace MLEM.Data.Json {
+    /// <summary>
+    /// A json type-safe wrapper can be used to wrap any objects of any type before submitting them to a non-specifically typed <see cref="List{T}"/> or <see cref="Dictionary{T,T}"/> that will be serialized using a <see cref="JsonSerializer"/> in cases where <see cref="JsonSerializer.TypeNameHandling"/> is not set to <see cref="TypeNameHandling.None"/>.
+    /// If any object is not wrapped in this manner, and it has a custom <see cref="JsonConverter"/>, the value deserialized from it might not have the same type as the originally serialized object. This behavior can be observed, for example, when serializing a <see cref="List{T}"/> of <see cref="object"/> entries, one of which is a <see cref="TimeSpan"/>: The <see cref="TimeSpan"/> will be serialized as a <see cref="string"/> and, upon deserialization, will remain a <see cref="string"/>.
+    /// In general, wrapping objects in this manner is only useful in rare cases, where custom data of an unexpected or unknown type is stored.
+    /// See <see cref="JsonTypeSafeGenericDataHolder"/> for an example of how this class and <see cref="JsonTypeSafeWrapper{T}"/> can be used, and see this stackoverflow answer for more information on the problem that this class solves: https://stackoverflow.com/a/38798114.
+    /// </summary>
+    public abstract class JsonTypeSafeWrapper {
+
+        /// <summary>
+        /// Returns this json type-safe wrapper's value as an <see cref="object"/>.
+        /// </summary>
+        public abstract object Value { get; }
+
+    }
+
+    /// <inheritdoc />
+    [DataContract]
+    public class JsonTypeSafeWrapper<T> : JsonTypeSafeWrapper {
+
+        /// <inheritdoc />
+        public override object Value => this.value;
+        [DataMember]
+        private readonly T value;
+
+        /// <summary>
+        /// Creates a new json type-safe wrapper instance that wraps the given <paramref name="value"/>.
+        /// </summary>
+        /// <param name="value">The value to wrap</param>
+        public JsonTypeSafeWrapper(T value) {
+            this.value = value;
+        }
+
+    }
+}

MLEM.Ui/Style/UiStyle.cs

@@ -11,7 +11,7 @@ namespace MLEM.Ui.Style {
     /// <summary>
     /// The style settings for a <see cref="UiSystem"/>.
     /// Each <see cref="Element"/> uses these style settings by default, however you can also change these settings per element using the elements' individual style settings.
-    /// Note that this class is a <see cref="GenericDataHolder"/>, meaning additional styles for custom components can easily be added using <see cref="GenericDataHolder.SetData"/>
+    /// Note that this class is a <see cref="GenericDataHolder"/>, meaning additional styles for custom components can easily be added using <see cref="GenericDataHolder.SetData{T}"/>
     /// </summary>
     public class UiStyle : GenericDataHolder {
 

MLEM/Misc/GenericDataHolder.cs

@@ -11,8 +11,8 @@ namespace MLEM.Misc {
         private Dictionary<string, object> data;
 
         /// <inheritdoc />
-        public void SetData(string key, object data) {
+        public void SetData<T>(string key, T data) {
-            if (data == default) {
+            if (EqualityComparer<T>.Default.Equals(data, default)) {
                 if (this.data != null)
                     this.data.Remove(key);
             } else {
@@ -30,7 +30,7 @@ namespace MLEM.Misc {
         }
 
         /// <inheritdoc />
-        public IReadOnlyCollection<string> GetDataKeys() {
+        public IEnumerable<string> GetDataKeys() {
             if (this.data == null)
                 return Array.Empty<string>();
             return this.data.Keys;
@@ -49,7 +49,8 @@ namespace MLEM.Misc {
         /// </summary>
         /// <param name="key">The key to store the data by</param>
         /// <param name="data">The data to store in the object</param>
-        void SetData(string key, object data);
+        /// <typeparam name="T">The type of the data to store</typeparam>
+        void SetData<T>(string key, T data);
 
         /// <summary>
         /// Returns a piece of generic data of the given type on this object.
@@ -63,7 +64,7 @@ namespace MLEM.Misc {
         /// Returns all of the generic data that this object stores.
         /// </summary>
         /// <returns>The generic data on this object</returns>
-        IReadOnlyCollection<string> GetDataKeys();
+        IEnumerable<string> GetDataKeys();
 
     }
 }

Tests/DataTests.cs

@@ -92,6 +92,31 @@ namespace Tests {
             Assert.AreEqual(Or(flags[24], flags[43]).ToString(), "Flag24 | Flag43");
         }
 
+        [Test]
+        public void TestJsonTypeSafety() {
+            var serializer = new JsonSerializer {TypeNameHandling = TypeNameHandling.Auto};
+
+            // normal generic data holder should crush the time span down to a string due to its custom serializer
+            var data = new GenericDataHolder();
+            data.SetData("Time", TimeSpan.FromMinutes(5));
+            var read = SerializeAndDeserialize(serializer, data);
+            Assert.IsNotInstanceOf<TimeSpan>(read.GetData<object>("Time"));
+            Assert.Throws<InvalidCastException>(() => read.GetData<TimeSpan>("Time"));
+
+            // json type safe generic data holder should wrap the time span to ensure that it stays a time span
+            var safeData = new JsonTypeSafeGenericDataHolder();
+            safeData.SetData("Time", TimeSpan.FromMinutes(5));
+            var safeRead = SerializeAndDeserialize(serializer, safeData);
+            Assert.IsInstanceOf<TimeSpan>(safeRead.GetData<object>("Time"));
+            Assert.DoesNotThrow(() => safeRead.GetData<TimeSpan>("Time"));
+        }
+
+        private static T SerializeAndDeserialize<T>(JsonSerializer serializer, T t) {
+            var writer = new StringWriter();
+            serializer.Serialize(writer, t);
+            return serializer.Deserialize<T>(new JsonTextReader(new StringReader(writer.ToString())));
+        }
+
         private class TestObject {
 
             public Vector2 Vec;