ajv-validation-deprecated-keyword.js

// this shows how we can extend AJV@8 to report <deprecated> properties as warnings

const Ajv = require('ajv');

const ajv = new Ajv({
  allErrors: true
});

const schema = {
  type: 'object',
  properties: {
    country: { type: 'string' },
    city: { type: 'string', deprecated: true }
  },
  required: ['country']
};

ajv.removeKeyword('deprecated');

ajv.addKeyword({
  keyword: 'deprecated',
  modifying: true,
  compile(schema, parentSchema, it) {
    return function (data, dataCtx) {
      if (schema === true && data !== undefined) {
        return false;
      }
      return true;
    };
  },
  errors: false
});

const validate = ajv.compile(schema);

const data = {
  country: 'USA',
  city: 'New York'
};

const valid = validate(data);

const [
  errors,
  warnings
] = (validate.errors || []).reduce(
  ([ errors, warnings ], error) =>
    error.keyword !== 'deprecated'
      ? [ [ ...errors, error ], warnings ]
      : [ errors, [ ...warnings, error ] ],
  [ [], [] ]
);

if (!errors.length) {
  console.log('Validation succeeded!');
} else {
  console.log('Validation errors:', errors);
}

console.log('Validation warnings:', warnings);