Handle creation of missing nested objects for JSON MergePatch

src/Tingle.AspNetCore.JsonPatch/Internal/ObjectVisitor.cs

@@ -49,6 +49,12 @@ public bool TryVisit(ref object target, [NotNullWhen(true)] out IAdapter? adapte
                 }
             }
 
+            // If we hit a null on an interior segment but we can create, then we should try to create.
+            if (next == null && create)
+            {
+                adapter.TryCreate(target, path.Segments[i], serializerOptions, out next, out errorMessage);
+            }
+
             // If we hit a null on an interior segment then we need to stop traversing.
             if (next == null)
             {

src/Tingle.AspNetCore.JsonPatch/JsonMergePatchDocumentOfT.cs

@@ -30,21 +30,23 @@ public JsonMergePatchDocument(List<Operation<TModel>> operations, JsonSerializer
     /// Apply this JsonMergePatchDocument
     /// </summary>
     /// <param name="objectToApplyTo">Object to apply the JsonMergePatchDocument to</param>
-    public void ApplyTo(TModel objectToApplyTo)
+    /// <param name="create">Whether to create nested objects if they do not exist</param>
+    public void ApplyTo(TModel objectToApplyTo, bool create = true)
     {
         ArgumentNullException.ThrowIfNull(objectToApplyTo);
 
-        ApplyTo(objectToApplyTo, new ObjectAdapter(SerializerOptions, null, AdapterFactory.Default, create: true));
+        ApplyTo(objectToApplyTo, new ObjectAdapter(SerializerOptions, null, AdapterFactory.Default, create));
     }
 
     /// <summary>
     /// Apply this JsonMergePatchDocument
     /// </summary>
     /// <param name="objectToApplyTo">Object to apply the JsonMergePatchDocument to</param>
     /// <param name="logErrorAction">Action to log errors</param>
-    public void ApplyTo(TModel objectToApplyTo, Action<JsonPatchError> logErrorAction)
+    /// <param name="create">Whether to create nested objects if they do not exist</param>
+    public void ApplyTo(TModel objectToApplyTo, Action<JsonPatchError> logErrorAction, bool create = true)
     {
-        ApplyTo(objectToApplyTo, new ObjectAdapter(SerializerOptions, logErrorAction, AdapterFactory.Default, create: true), logErrorAction);
+        ApplyTo(objectToApplyTo, new ObjectAdapter(SerializerOptions, logErrorAction, AdapterFactory.Default, create), logErrorAction);
     }
 
     /// <summary>

tests/Tingle.AspNetCore.JsonPatch.Tests/JsonMergePatchDocumentConverterHelperTests.cs

@@ -159,47 +159,66 @@ public void Apply_Works()
         Assert.Equal("immigration", video.Description);
         Assert.Null(video.Name);
         Assert.Equal("123", video.Id);
+
+        video = new Video { Metadata = new() { ["primary"] = "cake", } };
+        doc = JsonSerializer.Deserialize<JsonMergePatchDocument<Video>>(node.ToJsonString(), serializerOptions)!;
+        var modelState = new ModelStateDictionary();
+        doc.ApplyToSafely(video, modelState);
+        Assert.True(modelState.IsValid);
+        Assert.Empty(modelState);
+
+        Assert.Equal("rudi shule", Assert.Contains("swa", video.Translations).Body);
+        Assert.Equal("google", Assert.Contains("swa", video.Translations).Provider);
+        Assert.Equal("hapa tu", Assert.Contains("primary", video.Metadata));
+        Assert.Equal("pale tu", Assert.Contains("secondary", video.Metadata));
+        Assert.Equal(["prod", "ken"], video.Tags);
+        Assert.Equal("immigration", video.Description);
+        Assert.Null(video.Name);
+        Assert.Equal("123", video.Id);
     }
 
     [Fact]
-    public void ApplyToSafely_Works()
+    public void Apply_Works_CreatesNodes()
     {
         var node = new JsonObject
         {
-            ["translations"] = new JsonObject
+            ["make"] = "Tesla",
+            ["model"] = "Model 3",
+            ["owner"] = new JsonObject
             {
-                ["swa"] = new JsonObject
+                ["name"] = "Elon Musk",
+                ["address"] = new JsonObject
                 {
-                    ["body"] = "rudi shule",
-                    ["provider"] = "google",
+                    ["country"] = "USA",
                 },
             },
-            ["metadata"] = new JsonObject
-            {
-                ["primary"] = "hapa tu",
-                ["secondary"] = "pale tu",
-            },
-            ["tags"] = new JsonArray { "prod", "ken", },
-            ["description"] = "immigration",
-            ["name"] = null,
         };
 
-        var video = new Video { Metadata = new() { ["primary"] = "cake", } };
+        var vehicle = new Vehicle { Make = "Toyota", Model = "Corolla" };
         var serializerOptions = new JsonSerializerOptions(JsonSerializerDefaults.Web);
-        var doc = JsonSerializer.Deserialize<JsonMergePatchDocument<Video>>(node.ToJsonString(), serializerOptions)!;
+        var doc = JsonSerializer.Deserialize<JsonMergePatchDocument<Vehicle>>(node.ToJsonString(), serializerOptions)!;
+        doc.ApplyTo(vehicle);
+
+        Assert.Equal("Tesla", vehicle.Make);
+        Assert.Equal("Model 3", vehicle.Model);
+        Assert.NotNull(vehicle.Owner);
+        Assert.Equal("Elon Musk", vehicle.Owner.Name);
+        Assert.NotNull(vehicle.Owner.Address);
+        Assert.Equal("USA", vehicle.Owner.Address.Country);
+
+        vehicle = new Vehicle { Make = "Toyota", Model = "Corolla" };
+        doc = JsonSerializer.Deserialize<JsonMergePatchDocument<Vehicle>>(node.ToJsonString(), serializerOptions)!;
         var modelState = new ModelStateDictionary();
-        doc.ApplyToSafely(video, modelState);
+        doc.ApplyToSafely(vehicle, modelState);
         Assert.True(modelState.IsValid);
         Assert.Empty(modelState);
 
-        Assert.Equal("rudi shule", Assert.Contains("swa", video.Translations).Body);
-        Assert.Equal("google", Assert.Contains("swa", video.Translations).Provider);
-        Assert.Equal("hapa tu", Assert.Contains("primary", video.Metadata));
-        Assert.Equal("pale tu", Assert.Contains("secondary", video.Metadata));
-        Assert.Equal(["prod", "ken"], video.Tags);
-        Assert.Equal("immigration", video.Description);
-        Assert.Null(video.Name);
-        Assert.Equal("123", video.Id);
+        Assert.Equal("Tesla", vehicle.Make);
+        Assert.Equal("Model 3", vehicle.Model);
+        Assert.NotNull(vehicle.Owner);
+        Assert.Equal("Elon Musk", vehicle.Owner.Name);
+        Assert.NotNull(vehicle.Owner.Address);
+        Assert.Equal("USA", vehicle.Owner.Address.Country);
     }
 
     class Video
@@ -217,4 +236,22 @@ class VideoTranslation
         public string? Body { get; set; }
         public string? Provider { get; set; }
     }
+
+    class Vehicle
+    {
+        public string? Make { get; set; }
+        public string? Model { get; set; }
+        public VehicleOwner? Owner { get; set; }
+    }
+
+    class VehicleOwner
+    {
+        public string? Name { get; set; }
+        public VehicleOwnerAddress? Address { get; set; }
+    }
+
+    class VehicleOwnerAddress
+    {
+        public string? Country { get; set; }
+    }
 }