fix for issue 88 (#89)

Co-authored-by: Reece Bradley <[email protected]>

src/Hyperbee.Json/Patch/JsonPatch.cs

@@ -416,12 +416,13 @@ private static void ThrowLocationDoesNotExist( string path, JsonNode node )
 
     private static JsonNode PatchValue( PatchOperation patch )
     {
-        if ( patch.Value is null )
-            throw new JsonPatchException( "The 'value' property was missing." );
-
-        return (patch.Value is JsonNode node)
-            ? (node.Parent != null ? node.DeepClone() : node)
-            : JsonValue.Create( patch.Value );
+        return patch.Value switch
+        {
+            null => null,
+            JsonNode node when node.Parent != null => node.DeepClone(),
+            JsonNode node => node,
+            _ => JsonValue.Create( patch.Value )
+        };
     }
 
     public IEnumerator<PatchOperation> GetEnumerator()

test/Hyperbee.Json.Tests/Patch/JsonPatchTests.cs

@@ -1,5 +1,4 @@
-using System;
-using System.Text.Json.Nodes;
+using System.Text.Json.Nodes;
 using Hyperbee.Json.Patch;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 
@@ -885,6 +884,25 @@ public void Replace_WhenValueProperty()
         Assert.AreEqual( "Mark", source!["first"]!.GetValue<string>() );
     }
 
+    [TestMethod]
+    public void Replace_WhenValueProperty_WithNull()
+    {
+        var source = JsonNode.Parse(
+            """
+            {
+                "first": "John"
+            }
+            """ );
+
+        var patch = new JsonPatch(
+            new PatchOperation( PatchOperationType.Replace, "/first", null, null )
+        );
+
+        patch.Apply( source );
+
+        Assert.AreEqual( null, source!["first"] );
+    }
+
     [TestMethod]
     public void Replace_WhenValueObject()
     {