Extending a schema

[bsiddiqui]

Is there a way to overwrite a key in the schema or add to the validation parameter?

Overwrite a key:

var base = Joi.object().keys({
    a: Joi.number(),
    b: Joi.string()
});

var extended = base.keys({
    a: Joi.string()
});

Add a parameter:

var base = Joi.object().keys({
    a: Joi.number(),
    b: Joi.string()
});

var extended = base.keys({
    a: Joi.number().min(10)
});

[danielb2]

FYI, if the object is top level, you can use a regular object as opposed to a Joi.object()

But this looks like a bug. I would think the desired behavior is what @bsiddiqui is looking for

var Joi = require('./');

var base = Joi.object().keys({
    a: Joi.number(),
    b: Joi.string()
});
var extended = base.keys({ a: Joi.boolean() });

> Joi.assert({ a: 3, b: 'sdcsd'}, extended);
Error: {
  "b": "sdcsd",
  "a" [1]: 3
}
[1] "a" must be a boolean

> Joi.assert({ a: true, b: 'sdcsd'}, extended);
Error: {
  "b": "sdcsd",
  "a" [1]: true
}
[1] "a" must be a number

[danielb2]

test case

      it('alters existing keys', function (done) {

          var a = Joi.object({ a: 1 });
          var b = a.keys({ a: 2 });

          b.validate({ a: 1 }, function (err, value) {

              expect(err).to.exist();
              b.validate({ a: 2 }, function (err2, value2) {

                  expect(err2).to.not.exist();
                  done();
              });
          });
      });

[danielb2]

Or alternatively, it should give an error when trying to alter the key

[Marsup]

Is there a question here ? Looks like you put the question and answers in the same post.
You can also use concat to add on existing keys.

[bsiddiqui]

@Marsup I put what I'd expect the result to be but that's now how Joi is working for me

var base = Joi.object().keys({
    a: Joi.number(),
    b: Joi.string()
});

var extended = base.keys({
    a: Joi.string()
});

Joi.validate({ a: 'hello' }, extended)
// => ValidationError: child "a" fails because ["a" must be a number]

I would expect extended's schema to overwrite base