Joi.any().when is not evaluated if empty

[asafdav]

Joi.any().when is not evaluated it its value is empty even if the when condition is fulfilled.

For example:

 Joi.object({
   a: Joi.string().when('b', {is: true, then: Joi.required()}),
   b: Joi.boolean().default(false)
})

If you use this object to validate {b: true} the returned value will remain {b: true} but it actually should return an error.

[hueniverse]

You should follow the rules of the bug hunt and open a failing test. The fix is not right but the issue looks valid.

[asafdav]

Sure, I will create the test, sorry for that.

I just wonder why you say the fix is not right, I'd love to learn from that.

I went through the code, and as long as "undefined" is in the "valid" list, when an empty value will be received it will automatically pass.

I saw how any().required is implemented and figured I can use the same method. Logically it makes sense to say that fields with "when" clause must be evaluated on every validation cycle.

I tried and saw that my fix didn't break anything, and it actually solved my issue.

Thanks in advance.

[hueniverse]

Take a look at the commit above. This was a bit more complex. First, normal alternative doesn't require a match by default if the key is missing so the change belonged in the any.when(), not in the alternatives.when(). Second, once you add that change, the otherwise case breaks due to bad logic in concat().

[hueniverse]

Looking at your actual failing test, I am not sure what's the right solution for that one. Basically, you can now (with the fix) make this work by removing alternatives() (just Joi.when()). Calling when() directly on an alternatives type doesn't do what you expect it to. I need to think about this and if this is a bug for an edge case or not. Either way, the core of the issue was a confirmed bug.

[asafdav]

I see, I'm glad I could make you think :)

Thanks for the elaborate explanation and for the workaround!