JsonExtensionDataPatchDocumentAdapter

is a .NET package that transforms operation paths in JsonPatchDocuments such that they match the annotated JsonExtensionData property.

Installation

Install it from nuget JsonPatchDocumentExtensionDataAdapter:

dotnet add package JsonPatchDocumentExtensionDataAdapter 

Version	Number
Stable

Motivation

Assume you have a model class that uses the JsonExtensionData attribute to store additional properties that are not part of the model.

class MyClass
{
    public int? Foo { get; set; }
    public string? Bar { get; set; }

    [System.Text.Json.Serialization.JsonExtensionData]
    public IDictionary<string, object>? MyExtensionData { get; set; }
}

Assume, you have an ASP.NET Core Server, that consumes JsonPatchDocument<MyClass> to update the model with an RFC6902 HTTP PATCH request (docs):

public IActionResult<MyClass> Patch([FromBody] JsonPatchDocument<MyClass> patch)
{
    var myClass = new MyClass();
    patch.ApplyTo(myClass);
    return Ok(myClass);
}

If the client sends a PATCH request with the following body to your server:

[
    {
        "op": "add",
        "path": "/AnUnmappedProperty",
        "value": "MyValue"
    }
]

The .ApplyTo(...) will fail with a JsonPatchException:

The target location specified by path segment 'AnUnmappedProperty' was not found.

If the client sent the following body instead:

[
    {
        "op": "add",
        "path": "/MyExtensionData/AnUnmappedProperty",
        "value": "MyValue"
    }
]

it would work, but the client doesn't and shouldn't know about the MyExtensionData property as it's transparent to the client.

Use of this library

This library provides an adapter that transforms the paths in a given JsonPatchDocument such that they match the JsonExtensionData property.

using JsonExtensionDataPatchDocumentAdapter;
// ...

public IActionResult<MyClass> Patch([FromBody] JsonPatchDocument<MyClass> patch)
{
    var myClass = new MyClass();
    var modifiedPatch = patch.Adapt(x=>x.MyExtensionData, myClass);
    modifiedPatch.ApplyTo(myClass); // no longer raises a JsonPatchException
    return Ok(myClass);
}