Nullable type support for 'anyOf' fields with two values

[aringeri]

Prerequisites

• I have read the documentation

What theme are you using?

shadcn

What is your question?

Hello,

I have a specific use-case where my nullable types are represented with an anyOf but do not want to render them as a drop-down with two options (null, string).

For context, I am using FastAPI to generate an OpenAPI/JSONSchema specification for my backend API. Using FastAPI, Nullable/Optional properties are generated into JSONSchema as below (playground):

"name": {
  "anyOf": [
    {
      "type": "string"
    },
    {
      "type": "null"
    }
  ],
  "title": "Name",
  "description": "A name of a user"
}

I understand that react-jsonschema-form is expecting nullable types to use an array (in order to render a single textbox) as below (playground):

"name": {
  "type": [ "string", "null" ],
  "title": "Name",
  "description": "A name of a user"
}

Is there any way to configure react-jsonschema-form for the first case to render only a single text box? I see this as a specific case where there are only two options in an anyOf/oneOf property, and one of those options is null.

Any help would be appreciated!

[heath-freenome]

@aringeri I understand that you'd like us to write a special case handling of anyOf where only type is provided and convert that into type: [<any of values>]. Is it possible to modify your schemas instead? Maybe use a custom_encoder to detect that condition and replace with the types? It would be possible for us to do this one specific transformation deep in the bowels of our schema management utilities, and I would rather not have to do that. You are welcome to push up PR yourself in the retrieveSchema.ts sourcefile.

[aringeri]

Hi @heath-freenome,
Thanks for your response. I'm not sure I want you to generally convert anyOf to a type: [<any of values>]. Instead I am wondering whether this tool should treat the specific case where an anyOf definition is equivalent (semantically) to a nullable value: ("anyOf": [ {"type": <some-type> }, {"type": "null"}])

But anyway, after some investigation it seems there are ways to configure how FastAPI exports their OpenAPI schemas: fastapi/fastapi#14264
Essentially, I annotate each optional property that I want to export in the schema as: "type": [ "string", "null" ]

I am still assessing whether this approach will be feasible for my project.

[heath-freenome]

@aringeri it seems like the post-processor approach would be the best solution for you. Or could you support type: string , nullable: true which was mentioned at the end of the issue?