toJsonSchema array fields conversion. Should `items` be an object?

[kolyasya]

I'm trying to build up a client-side form with https://github.com/rjsf-team/react-jsonschema-form To do so I'm using SimplSchema → JSON Schema conversion.

And for array fields I noticed that I don't get a proper result. This issue mostly refers to this line — https://github.com/longshotlabs/simpl-schema/blob/555f790ad17ed15d600d5e1b9bbb1132476f4cd1/src/toJsonSchema.ts#L14

If I start with such schema:

const animals = new SimpleSchema({
  animals: { type: Array },
  'animals.$': { type: Object },
  'animals.$.label': { type: String },
});

I get a JSONSchema:

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "properties": {
    "animals": {
      "type": "array",
      "items": [
        {
          "type": "object",
          "properties": {
            "label": {
              "type": "string"
            }
          },
          "required": ["label"],
          "additionalProperties": false
        }
      ],
      "additionalItems": false
    }
  },
  "required": ["animals"],
  "additionalProperties": false
}

And if I use this JSON schema directly with formData:

{
  "animals": [
    {
      "label": "Cat"
    },
    {
      "label": "Dog"
    },
    {
      "label": "Whale"
    }
  ]
}

I get only a single item:

This is because items of the same shape should be defined as an object, not array: https://json-schema.org/learn/getting-started-step-by-step#optional

Am I thinking about that wrong or is this a bug?

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