Calling .AddSystemTextJsonMergePatch() adds the application/merge-patch+json as default option in Swagger

[harvzor]

After calling .AddSystemTextJsonMergePatch() in the startup, it adds the application/merge-patch+json content type to Swagger.

However, this means that other endpoints will default to this type, even if they're not PATCH:

[HttpPut("broken/{id:int}")]
public IActionResult BrokenUpdateCustomer([FromRoute] int id, [FromBody] BrokenCustomerPutDto brokenCustomerPutDto)
{
    // ...
}

Probably it defaults to this because the list is in alphabetical order:

I think this is more of an issue on Swashbuckle's side. I'm not expecting this to be fixed (probably it can't be fixed here) - I just wanted this to be documented 😄

Workaround

Put [Consumes(MediaTypeNames.Application.Json)] on either every other method that accepts a body, or just apply it to the class:

[Consumes(MediaTypeNames.Application.Json)]
public class CustomersController : ControllerBase
{
    // ...
}

[Morcatko]

Interesting.
I never noticed it.
It seems to show all content types even if I remove AddNewtonsoftJsonMergePatch and comment out all non-default settings in swagger options in my application.

It looks like it is really a swagger issue but I have no time right now to investigate more.

[poizan42]

That's because SystemTextJsonMergePatchInputFormatter does not implement GetSupportedContentTypes. It essentially declares that it supports every possible model type, which in reality it does not as its just going to fail on either getting the generic arguments of a non-generic type at

Morcatko.AspNetCore.JsonMergePatch/src/6.0-JsonMergePatch.SystemText/SystemTextJsonMergePatchInputFormatter.cs

Line 97 in 09d5971

var modelType = jsonMergePatchType.GenericTypeArguments[0];

or the cast at

Morcatko.AspNetCore.JsonMergePatch/src/6.0-JsonMergePatch.SystemText/SystemTextJsonMergePatchInputFormatter.cs

Line 47 in 09d5971

var e = (JsonElement)o;

[Morcatko]

Thanks for the fix. It will be available as v6.0.2 soon