[OpenApi] Generate schema for JSON Patch endpoints

[martincostello]

Generate schema for JSON Patch endpoints

Generate an OpenAPI schema for JSON Patch endpoints.

Description

Follow-up for #62988 (comment).

I did a bit Googling and came up with a schema that's a synthesis of different examples I found. It could potentially be simplified to not use OneOf.

I couldn't see any obvious reason to generate a different schema for JsonPatchDocument<T> compared to JsonPatchDocument as the patch schema is the same for both as it isn't strongly-typed to the document being patched, so both use the same schema.

Tested locally by adding SwaggerUI to the Sample App and viewing the operation generated, then using the sample request as-is and submitting it and inspecting the in-memory document in the debugger to check that it was deserialized correctly and all seems to work as expected.

[Copilot]

Pull Request Overview

This PR adds OpenAPI schema generation support for JSON Patch endpoints by implementing a dedicated schema for JsonPatchDocument and JsonPatchDocument<T> types. The implementation follows the JSON Patch RFC 6902 specification to generate appropriate OpenAPI documentation.

Key changes:

• Adds specialized schema generation for JSON Patch documents with proper operation structures (add, replace, test, move, copy, remove)
• Uses the same schema for both generic and non-generic JsonPatchDocument types since the patch format is identical
• Sets default media type to "application/json-patch+json" for JSON Patch parameters

Reviewed Changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/OpenApi/src/Services/Schemas/OpenApiSchemaService.cs	Implements the core JSON Patch schema generation logic with operation-specific structures
src/OpenApi/src/Services/OpenApiDocumentService.cs	Adds default media type handling for JSON Patch parameters
src/OpenApi/src/Services/OpenApiGenerator.cs	Updates parameter detection to recognize JSON Patch types as body parameters
src/OpenApi/src/Extensions/JsonTypeInfoExtensions.cs	Maps both JsonPatchDocument types to the same schema name
src/OpenApi/src/Microsoft.AspNetCore.OpenApi.csproj	Adds reference to JsonPatch.SystemTextJson package
Test files	Comprehensive test coverage for various JSON Patch scenarios and edge cases

[martincostello]

Looks like adding Microsoft.AspNetCore.JsonPatch.SystemTextJson as a dependency of Microsoft.AspNetCore.OpenApi causes trim warnings as the former is not AoT compatible but the latter is.

Having a quick look at JsonPatch there's a tonne of object in there and I don't think it can be made trivially AoT compatible (it would probably need a source generator?).

A workaround might be to remove the dependency and instead check on the type name, even though that's ick.

[captainsafia]

Looks like adding Microsoft.AspNetCore.JsonPatch.SystemTextJson as a dependency of Microsoft.AspNetCore.OpenApi causes trim warnings as the former is not AoT compatible but the latter is.

Yep, I figured this problem would come up. 😅 I think the workaround of a type name + assembly name check is probably sufficient for now. In an ideal world, the M.A.JP.STJ package would've been trim-friendly to start but that didn't end up being the chase. :/

[captainsafia]

Looks good overall! Left some small comments about a tweak to the schema. Would also like @mikekistler to chime in on the proposed schema here.

[martincostello]

Addressed feedback. Also explains why I didn't spot #63073 in this PR, as it updates the snapshots which inadvertently fixes the test (you can see in the diff for that file it only adds, while the other two also have deletes).

[mikekistler]

This looks great! Thanks @martincostello !