added a json extension to mlem.data for easy json property modification

MLEM.Data/Json/JsonExtensions.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Reflection;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Serialization;
+
+namespace MLEM.Data.Json {
+    /// <summary>
+    /// A set of extensions for dealing with the Newtonsoft.JSON <see cref="JsonSerializer"/>.
+    /// </summary>
+    public static class JsonExtensions {
+
+        /// <summary>
+        /// Changes the <see cref="JsonSerializer.ContractResolver"/> to a contract resolver that queries each newly created <see cref="JsonProperty"/> and allows modifying it easily.
+        /// This removes the need to create a new contract resolver class for modifying created json properties.
+        /// </summary>
+        /// <param name="serializer">The serializer to which to add the property modifier</param>
+        /// <param name="propertyModifier">A function that takes in the json property and allows returning a modified property (or the same one)</param>
+        /// <returns></returns>
+        public static JsonSerializer SetPropertyModifier(this JsonSerializer serializer, Func<JsonProperty, JsonProperty> propertyModifier) {
+            serializer.ContractResolver = new PropertyModifierResolver(propertyModifier);
+            return serializer;
+        }
+
+        private class PropertyModifierResolver : DefaultContractResolver {
+
+            private readonly Func<JsonProperty, JsonProperty> propertyModifier;
+
+            public PropertyModifierResolver(Func<JsonProperty, JsonProperty> propertyModifier) {
+                this.propertyModifier = propertyModifier;
+            }
+
+            protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization) {
+                var property = base.CreateProperty(member, memberSerialization);
+                return this.propertyModifier(property);
+            }
+
+        }
+
+    }
+}