group-array with required parent fails for empty array, despite minItems: 0

[mariada-ta]

Description:
I’m using remotess json-schema-form in my vue project. The schema I created has a parent array property ("inputType": "group-array") which is required, but the array itself can be empty (minItems: 0).

Look here:

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "properties": {
    "sources": {
      "title": "Sources",
      "type": "array",
      "x-jsf-presentation": {
        "inputType": "group-array",
        "min": 0,
        "max": 61
      },
      "items": {
        "type": "object",
        "properties": {
          "index": {
            "type": "integer",
            "title": "index",
            "minimum": 1,
            "maximum": 62,
            "x-jsf-presentation": {
              "inputType": "number",
              "min": 1,
              "max": 62
            }
          },
          "device": {
            "type": "integer",
            "title": "Device",
            "minimum": 1,
            "maximum": 62,
            "x-jsf-presentation": {
              "inputType": "number",
              "default": 1,
              "min": 1,
              "max": 62
            }
          }
        },
        "required": [
          "device",
          "index"
        ],
        "additionalProperties": false
      },
      "minItems": 0,
      "maxItems": 61,
      "uniqueItems": true
    }
  },
  "required": [
    "sources"
  ],
  "additionalProperties": false
}

Problem:
When I validate the following json: {"sources":[]} it always says {"sources":"Required field"} and the problem is only gone, when I remove the "required": [
"sources"
]

I added a small vue example showing my issue, I would appreciate every bit of help.

bug_empty_required_json.zip

[sandrina-p]

Hi @mariada-ta! That's indeed a bug. We currently don't have bandwidth to fix but, could you give it a try? It's somewhere in the validateSchema function

[mariada-ta]

I looked into the problem and would have fixed it like this:
File: src/validation/schema.ts
Line: 241 - 263

 if (schema.required && isObjectValue(value)) {
    const missingKeys = schema.required.filter((key: string) => {
      const fieldValue = value[key]
      const fieldSchema = schema.properties?.[key]
      // Field is considered missing if:
      // - it's undefined OR
      // - it's null AND treatNullAsUndefined option is true
      // - it's an array/object and it's empty
      if (Array.isArray(fieldValue)) {
        if (fieldSchema && getSchemaType(fieldSchema) === 'array') {
          const minItems = (fieldSchema as any).minItems ?? 0
          return fieldValue.length < minItems
        }
        return fieldValue.length === 0
      }

      if (isObjectValue(fieldValue)) {
        return Object.keys(fieldValue).length === 0
      }

      return fieldValue === undefined || (fieldValue === null && options.treatNullAsUndefined)
    })

I added a check that looks to see if there is a minItems attribute in the property and, if so, whether the element meets the length requirement. This means that an empty array with minItems: 0 is now correct.