Ajv custom error message for type

Question

i was exploring Ajv with ajv-errors for validating json schema and producing custom error messages. everything works as of now but i can't set custom error message for type for individual values.

const emailSchema = {
 type: 'object',
 required: ['foo', 'bar', 'car'],
 properties: {
  foo: { type: 'integer' },
  bar: { type: 'string' },
  car: { type: 'string' }
 },
 errorMessage: {
  type: 'should be an object',
  required: {
  foo: 'foo field is missing',
  bar: 'bar field is missing',
  car: 'car field is missing'
  }
 } 
};

outputs following error

[
    {
        "keyword": "type",
        "dataPath": "/foo",
        "schemaPath": "#/properties/foo/type",
        "params": {
            "type": "integer"
        },
        "message": "should be integer"
    },
    {
        "keyword": "errorMessage",
        "dataPath": "",
        "schemaPath": "#/errorMessage",
        "params": {
            "errors": [
                {
                    "keyword": "required",
                    "dataPath": "",
                    "schemaPath": "#/required",
                    "params": {
                        "missingProperty": "bar"
                    },
                    "message": "should have required property 'bar'"
                }
            ]
        },
        "message": "bar field is missing"
    },
    {
        "keyword": "errorMessage",
        "dataPath": "",
        "schemaPath": "#/errorMessage",
        "params": {
            "errors": [
                {
                    "keyword": "required",
                    "dataPath": "",
                    "schemaPath": "#/required",
                    "params": {
                        "missingProperty": "car"
                    },
                    "message": "should have required property 'car'"
                }
            ]
        },
        "message": "car field is missing"
    }
]

the first error object with message "should be integer", can i customize it like foo must be an Integer. I am expecting something like below but it gives be schema error.

type : {
  foo : "foo must be an Integer"
}

Thanks.

Answer 1

You must declare errorMessage as keyword inside each of properties, see this example:

const emailSchema = {
  type: 'object',
  required: ['foo', 'bar', 'car'],
  properties: {
    foo: {
      type: 'integer',
      errorMessage: {
        // In here must be errorMessage not errorMessages
        type: 'foo must be an Integer', // Your Custom Error Message
      },
    },
    bar: { type: 'string' },
    car: { type: 'string' },
  },
  errorMessages: {
    // Change from errorMessage to errorMessages
    type: 'should be an object',
    required: {
      foo: 'foo field is missing',
      bar: 'bar field is missing',
      car: 'car field is missing',
    },
  },
}