Overriding formDataBodySerializer via config

[Marsunpaisti]

Description

Context why I have a problem in the first place:
I have a .NET backend that expects objects in form data to be in flattened dot notation such that the following applies:

{
  "primitiveKey": "fizzbuzz",
  "objectKey" : {
      "nestedKey1": "nestedValue1",
      "nestedKey2": "nestedValue2"
  }
}

// How it's currently added to form data:
primitiveKey = "fizzbuzz"
objectKey = "{\"nestedKey1\": \"nestedValue1\", \"nestedKey2\": \"nestedValue2\" }"

// How .NET expects it to be
primitiveKey = "fizzbuzz"
objectKey.nestedKey1 = "nestedValue1"
objectKey.nestedKey2 = "nestedValue2"

I need to override the default behavior of the form data body serializer but I can't find any way to accomplish this in the documentation. I can see that the client has a bodySerializer config, but I'm using the Tanstack Query plugin and it seems to directly pass a reference to the default generated body serializer in the generated mutations like below, so the bodySerializer of the client is not applied here:

/**
 * Upload documents
 */
export const uploadDocuments = <ThrowOnError extends boolean = false>(
	options: Options<UploadDocumentsData, ThrowOnError>
) => {
	return (options.client ?? client).post<UploadDocumentsResponses, unknown, ThrowOnError>({
		...formDataBodySerializer,
		responseTransformer: uploadDocumentsResponseTransformer,
		url: '/projects/{projectId}/documents',
		...options,
		headers: {
			'Content-Type': null,
			...options.headers
		}
	})
}

Is there any way to either configure it to override a specific serializer or to have it generate the flat form data format?

For now I did a dirty hack by just making script that replaces the import in the generated code with a serializer of my own, but it does feel like a hacky patch for something that seems like it would / should be configurable.

[dosubot]

Hi @Marsunpaisti! I'm Dosu and I’m helping the openapi-ts team.

There isn't any documented or supported way to override the formDataBodySerializer or generate flattened dot notation keys via config or plugin options in the OpenAPI TS codegen or the Tanstack Query plugin right now see docs. The Tanstack Query plugin lets you customize naming and casing patterns, but not the form data serialization logic itself see migration guide.

If you need the flattened format, your best bet is to manually modify the generated client code to swap in a custom serializer, or look for extension points in the generated code where you can inject your own logic. If your use case is critical, keep an eye on changelogs or discussions for future support of custom form data serialization.

To reply, just mention @dosu.

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