Added System.Text.Json serialization-based JsonPatch implementation

[mkArtakMSFT]

Fixes #24333

Design document: https://gist.github.com/mkArtakMSFT/346cf9d5c6eeb73406185751e28bd8fa

Benchmarks

I've a few benchmarks to compare this implementation with the original implementation and below are results for a few scenarios that I wanted to highlight.

Type	Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
ApplicationBenchmarks	NewtonsoftJsonPatch	271.924 us	5.4014 us	12.8370 us	1.9531	1.4648	-	25 KB
ApplicationBenchmarks	SystemTextJsonPatch	1.584 us	0.0307 us	0.0399 us	0.2365	-	-	3 KB
DeserializationBenchmarks	NewtonsoftJsonPatch	19.261 us	0.4241 us	1.2439 us	3.5095	0.0610	-	43 KB
DeserializationBenchmarks	SystemTextJsonPatch	7.917 us	0.3401 us	0.9866 us	0.5493	-	-	7 KB

[Copilot]

Pull Request Overview

This PR introduces a System.Text.Json-based JSON Patch implementation, adding new converters, adapters, and helper utilities to support JSON Patch operations using System.Text.Json.

• Implements a new JSON serialization-based approach for JSON Patch.
• Adds several converters for both generic and non-generic JSON Patch documents.
• Introduces utility classes and adapters to manipulate JSON structures and apply patch operations.

Reviewed Changes

Copilot reviewed 68 out of 73 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/Features/JsonPatch.SystemTextJson/src/Internal/ConversionResult.cs	New helper class for holding conversion results.
src/Features/JsonPatch.SystemTextJson/src/IJsonPatchDocument.cs	Defines the JSON Patch document interface with operations.
src/Features/JsonPatch.SystemTextJson/src/Helpers/JsonUtilities.cs	Provides a deep comparison utility for JSON objects.
src/Features/JsonPatch.SystemTextJson/src/Helpers/GenericListOrJsonArrayUtilities.cs	Utility methods for working with IList and JsonArray types.
src/Features/JsonPatch.SystemTextJson/src/Exceptions/JsonPatchException.cs	Custom exception class for JSON Patch errors.
src/Features/JsonPatch.SystemTextJson/src/Converters/OperationConverterOfT.cs	Converter for handling JSON Patch operations for generic types.
src/Features/JsonPatch.SystemTextJson/src/Converters/OperationConverterFactory.cs	Factory for creating operation converters.
src/Features/JsonPatch.SystemTextJson/src/Converters/JsonPatchDocumentConverterFactory.cs	Converter factory for both generic and non-generic JSON Patch documents.
src/Features/JsonPatch.SystemTextJson/src/Converters/JsonPatchDocumentConverter.cs	Converter for non-generic JsonPatchDocument.
src/Features/JsonPatch.SystemTextJson/src/Converters/JsonConverterForJsonPatchDocumentOfT.cs	Converter for generic JsonPatchDocument<T>.
src/Features/JsonPatch.SystemTextJson/src/Adapters/ObjectAdapter.cs	Implements core operations (add, remove, replace, move, copy, test) for patching objects.
src/Features/JsonPatch.SystemTextJson/src/Adapters/IObjectAdapterWithTest.cs	Interface for adapters supporting "test" operations.
src/Features/JsonPatch.SystemTextJson/src/Adapters/IObjectAdapter.cs	Base interface for JSON Patch operations on objects.
src/Features/JsonPatch.SystemTextJson/src/Adapters/IAdapterFactory.cs	Interface for adapter factory implementations.
src/Features/JsonPatch.SystemTextJson/src/Adapters/AdapterFactory.cs	Default factory for creating appropriate adapters based on target type.

Files not reviewed (5)

• AspNetCore.slnx: Language not supported
• src/Features/JsonPatch.SystemTextJson/.vsconfig: Language not supported
• src/Features/JsonPatch.SystemTextJson/JsonPatch.SystemTextJson.slnf: Language not supported
• src/Features/JsonPatch.SystemTextJson/build.cmd: Language not supported
• src/Features/JsonPatch.SystemTextJson/build.sh: Language not supported

Comments suppressed due to low confidence (2)

src/Features/JsonPatch.SystemTextJson/src/Converters/OperationConverterOfT.cs:13

• The override of CanConvert is redundant as it only returns the base implementation's result. Removing this override would simplify the code.

public override bool CanConvert(Type typeToConvert) { var result = base.CanConvert(typeToConvert); return result; }

src/Features/JsonPatch.SystemTextJson/src/Converters/JsonConverterForJsonPatchDocumentOfT.cs:15

• This CanConvert override is unnecessary since it directly calls and returns the base implementation's result. Consider removing it to reduce code redundancy.

public override bool CanConvert(Type typeToConvert) { var result = base.CanConvert(typeToConvert); return result; }

[mkArtakMSFT]

Thank you so much, @PranavSenthilnathan . I've adopted your converter implementation and the performance got so much better - much better than the original results I had with my implementation:

Type	Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
ApplicationBenchmarks	NewtonsoftJsonPatch	386.534 us	7.6784 us	13.4482 us	1.9531	0.9766	-	25 KB
ApplicationBenchmarks	SystemTextJsonPatch	2.418 us	0.0480 us	0.0913 us	0.2289	-	-	3 KB
DeserializationBenchmarks	NewtonsoftJsonPatch	27.165 us	0.5290 us	0.7917 us	3.5095	0.0610	-	43 KB
DeserializationBenchmarks	SystemTextJsonPatch	11.368 us	0.2243 us	0.4102 us	0.5493	-	-	7 KB

More specifically, the Deserialization with my original model was 2x slower than the Newtonsoft.Json-based model, and the update makes it more than 2x faster than Newtonsoft.Json one.

[PranavSenthilnathan]

Is it possible for one of the inputs to be a JsonElement representing null while the other is just CLR null?

[mkArtakMSFT]

Not sure, theoretically - maybe. I'd prefer to wait for actual feedback on this one from customers before trying to expand the implementation to cover that scenario too.