Defaults not applied from schema

I’m using a schema to create my settings, and I’ve been unable to have conf or electron-config use the defaults provided in the schema.

I’ve included a reduced test case here:

const Conf = require('conf');

const schema = {
  fizz: {
    type: 'string',
    default: 'buzz',
  },
  foo: {
    type: 'object',
    properties: {
      bar: {
        type: 'string',
        default: 'baz',
      },
    },
  },
};

const config = new Conf({schema});

console.log(config.get('fizz'));    // undefined - should be 'buzz'
console.log(config.get('foo'));     // undefined - should be { bar: 'baz' }
console.log(config.get('foo.bar')); // undefined - should be 'baz'

console.assert(config.get('fizz') === 'buzz');   // Assertion failed
console.assert(config.get('foo.bar') === 'baz'); // Assertion failed

An rough solution to populate defaults from schema is below, but I wouldn’t expect to have to do this when using a schema that includes defaults.

function setDefaults(schema, config, key_chain) {
  for (let [key, val] of Object.entries(schema)) {
    let this_key = (key_chain ? key_chain + '.' : '') + key;
    if (val.type === 'object') {
      return setDefaults(val.properties, config, this_key);
    }
    if (!config.has(key) && Object.hasOwnProperty.call(val, 'default')) {
      config.set(this_key, val.default);
    }
  }
}

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[sushantdhiman]

ajv maintainers has decided that default will not work for nested properties, if top level property has no default value

• https://github.com/ajv-validator/ajv/issues/1718
• https://github.com/ajv-validator/ajv/issues/1710

This issue should be closed, as this library is using useDefaults from ajv for this feature.

[YodaDaCoda]

@yaodingyd thanks, this has made me review my issue.

This is interesting. Adding default: {} to foo in my test above produces the desired results.

From what I can tell, draft 07 of the spec doesn’t define the behaviour of a validator in this regard. Draft 08 adds some examples that happen to include handling of defaults, and seems to imply that the results I expected are correct (i.e. able to specify defaults on a sub-property without specifying that the property is default: {}).

This sounds like an ajv issue. Can anyone with a better understanding than myself weigh in?