Use json-schema to require or disallow properties

问题:

What I'm trying to accomplish in json-schema: when the property enabled is true, certain other properties should be required. When false, those properties should be disallowed.

Here's my json-schema:

{
  "type": "object",
  "properties": {
    "enabled": { "type": "boolean" }
  },
  "required" : ["enabled"],
  "additionalProperties" : false,
  "if": {
    "properties": {
      "enabled": true
    }
  },
  "then": { 
    "properties": {
      "description" : { "type" : "string" },
      "count": { "type": "number" }
    },
    "required" : ["description", "count"]
  }
}

Validating using ajv version 6.5, this had the result of requiring count, etc. regardless of the value of enabled. For instance, for data:

{ "enabled": false }

My validation errors are:

[ { keyword: 'required',
    dataPath: '',
    schemaPath: '#/then/required',
    params: { missingProperty: 'description' },
    message: 'should have required property \'description\'' },
  { keyword: 'required',
    dataPath: '',
    schemaPath: '#/then/required',
    params: { missingProperty: 'count' },
    message: 'should have required property \'count\'' },
  { keyword: 'if',
    dataPath: '',
    schemaPath: '#/if',
    params: { failingKeyword: 'then' },
    message: 'should match "then" schema' } ]

How can I accomplish this using json-schema draft-7?

Note that this question is similar to, but has more stringent requirements than:
jsonSchema attribute conditionally required.

回答1:

Try this schema:

{
  "type": "object",
  "properties": {
    "enabled": {
      "type": "boolean"
    }
  },
  "required": [
    "enabled"
  ],
  "if": {
    "properties": {
      "enabled": {
        "const": true
      }
    }
  },
  "then": {
    "properties": {
      "enabled": {
        "type": "boolean"
      },
      "description": {
        "type": "string"
      },
      "count": {
        "type": "number"
      },
      "additionalProperties": false
    },
    "required": [
      "description",
      "count"
    ]
  },
  "else": {
    "properties": {
      "enabled": {
        "type": "boolean"
      }
    },
    "additionalProperties": false
  }
}

If you need "additionalProperties": false you have to enumerate all properties in both then and else. If you can accept additional properties the schema could be simplier:

{
  "type": "object",
  "properties": {
    "enabled": {
      "type": "boolean"
    }
  },
  "required": [
    "enabled"
  ],
  "if": {
    "properties": {
      "enabled": {
        "const": true
      }
    }
  },
  "then": {
    "properties": {
      "description": {
        "type": "string"
      },
      "count": {
        "type": "number"
      }
    },
    "required": [
      "description",
      "count"
    ]
  }
}

I checked with ajv cli.

Valid: {"enabled": false}

Invalid: {"enabled": true}

Valid: {"enabled": true, "description":"hi", "count":1}

回答2:

This was inspired by vearutop's excellent answer. I think it might be a little shorter, and accomplishes my stated purpose.

{
  "type": "object",
  "oneOf" : [
    {
      "properties": {
        "enabled": { "const": false }
      },
      "required": ["enabled"],
      "additionalProperties": false
    },
    {
      "properties": {
        "enabled": { "const": true },
        "description": { "type": "string" },
        "count": { "type": "number" }
      },
      "required": [ "enabled", "description", "count"],
      "additionalProperties": false
    }
  ]
}

As pointed out in the comments, this is a specific variant of the Enum strategy spelled out in this answer.

回答3:

To achieve that, in the if statement you need to use the const keyword, so the schema will look like:

{
  "type": "object",
  "properties": {
    "enabled": { "type": "boolean" }
  },
  "required" : ["enabled"],
  "additionalProperties" : false,
  "if": {
    "properties": {
      "enabled": {"const": true}
    }
  },
  "then": { 
    "properties": {
      "description" : { "type" : "string" },
      "count": { "type": "number" }
    },
    "required" : ["description", "count"]
  }
}