PropertyFilter ignored if a diffed object is null #48
Description
I am using SystemTextJson.JsonDiffPatch 2.0.0 on .Net 8.
Given this TestClass, I want diffs to include CompareMe and excludeIgnoreMe.
public class TestClass { public int CompareMe { get; set; } public int IgnoreMe { get; set; } } When both left and right are not null, the diff correctly excludes IgnoreMe.
public void BothNotNull() { TestClass left = new TestClass() { CompareMe = 1, IgnoreMe = 1 }; TestClass right = new TestClass() { CompareMe = 2, IgnoreMe = 2 }; string leftJson = JsonSerializer.Serialize(left); string rightJson = JsonSerializer.Serialize(right); JsonDiffOptions options = new JsonDiffOptions() { PropertyFilter = (prop, _) => !StringComparer.Ordinal.Equals(prop, nameof(TestClass.IgnoreMe)), }; JsonNode? diff = JsonDiffPatcher.Diff(leftJson, rightJson, options); string diffJson = diff!.ToJsonString(); // {"CompareMe":[1,2]} } But if one of left and right is null then the JsonDiffOptions.PropertyFilter function doesn't run and the diff includes IgnoreMe.
public void LeftNull() { TestClass? left = null; TestClass right = new TestClass() { CompareMe = 2, IgnoreMe = 2 }; string leftJson = JsonSerializer.Serialize(left); string rightJson = JsonSerializer.Serialize(right); JsonDiffOptions options = new JsonDiffOptions() { PropertyFilter = (prop, _) => !StringComparer.Ordinal.Equals(prop, nameof(TestClass.IgnoreMe)), }; JsonNode? diff = JsonDiffPatcher.Diff(leftJson, rightJson, options); string diffJson = diff!.ToJsonString(); // [null,{"CompareMe":2,"IgnoreMe":2}] // expected diffJson to be [null,{"CompareMe":2}] } public void RightNull() { TestClass left = new TestClass() { CompareMe = 1, IgnoreMe = 1 }; TestClass? right = null; string leftJson = JsonSerializer.Serialize(left); string rightJson = JsonSerializer.Serialize(right); JsonDiffOptions options = new JsonDiffOptions() { PropertyFilter = (prop, _) => !StringComparer.Ordinal.Equals(prop, nameof(TestClass.IgnoreMe)), }; JsonNode? diff = JsonDiffPatcher.Diff(leftJson, rightJson, options); string diffJson = diff!.ToJsonString(); // [{"CompareMe":1,"IgnoreMe":1},null] // expected diffJson to be [{"CompareMe":1},null] }