如何配置JSON Schema：无元素时不保留数组字段，禁用空对象数组

Got it, let's build the JSON Schema that fits your exact validation requirements. Here's a solution that covers all your cases, along with explanations of how each part works:

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "required": ["quantity"],
  "properties": {
    "quantity": {
      "type": "integer"
    },
    "modifiers": {
      "type": "array",
      "items": {
        "type": "object",
        "minProperties": 1
      },
      "minItems": 1
    }
  },
  "oneOf": [
    {
      "not": {
        "required": ["modifiers"]
      }
    },
    {
      "required": ["modifiers"]
    }
  ],
  "additionalProperties": false
}

Key Validation Logic Breakdown #

Let's walk through why this schema works for your rules:

• Mandatory quantity field: The required array ensures quantity is always present and typed as an integer.
• Prevent unexpected fields: additionalProperties: false blocks any extra fields not defined in the schema, keeping your JSON structure strict.
• Two mutually valid cases via oneOf:
  • No modifiers allowed: The first oneOf rule uses not: {required: ["modifiers"]} to enforce that if you don't intend to add modifiers, the field shouldn't exist at all.
  • Valid modifiers required when present: The second rule makes modifiers mandatory if it's going to be included, with these checks:
    • modifiers must be an array with at least one item (minItems: 1)
    • Every object in the modifiers array must have at least one key-value pair (minProperties: 1), which directly blocks empty objects like {} in the array.

Test Cases #

Let's verify against your examples:

• Valid (no modifiers):

  {"quantity": 3}
  

  Passes: No modifiers field, meets the first oneOf condition.

• Valid (with non-empty modifiers):

  {"quantity": 3, "modifiers": [{"testing": "some data here"}]}
  

  Passes: modifiers array contains a non-empty object, meets the second oneOf condition.

• Invalid (empty modifier object):

  {"quantity": 3, "modifiers": [{}]}
  

  Fails: The array item fails the minProperties: 1 check for modifier objects.

Additional invalid cases that get blocked:

• Empty modifiers array ({"quantity":3, "modifiers":[]})
• modifiers as a non-array value ({"quantity":3, "modifiers": {}})
• Extra fields not defined in the schema ({"quantity":3, "extraField": "test"})

内容的提问来源于stack exchange，提问作者CyberMew