Support intersections

[sguillia]

Support plan

• is this issue currently blocking your project? yes
• is this issue affecting a production system? no

Context

• node version: v12.4.0
• module version: joi 17.2.1
• environment (e.g. node, browser, native): node
• used with (e.g. hapi application, another framework, standalone, ...): standalone
• any other relevant information: n/a

How can we help?

Hi!

I can't find any way to write the schema for the following Typescript types. This is what I've tried:

import Joi from "@hapi/joi"

type Bar1 = {}
type Bar2 = {}
type Bar = Bar1 | Bar2
type Contents = {}
type Foo = Bar & Contents

const Bar1 = Joi.object()
const Bar2 = Joi.object()
const Bar = Joi.alternatives().try(Bar1, Bar2)
const Contents = Joi.object()
const Foo = Bar.concat(Contents) // compile error

It says

Argument of type 'ObjectSchema' is not assignable to parameter of type 'AlternativesSchema'.

Note I need to have 5 separate schemas, I cannot write one big schema mixing up all 5 types

Do you have any advice on how to approach the problem?

[nlundquist]

Running into the same library shortcoming. There needs to be someway to combine a set of alternatives with another schema.

My use case is slightly different

const Foo = Joi.object({ foo: Joi.string().required() }).unknown() 
const Bar = Joi.object({ bar: Joi.string().required() }).unknown() 
const Baz = Joi.object({ baz: Joi.string().required() }).unknown()
const Buz = Joi.object({ buz: Joi.string().required() }).unknown()

// will compile, but when alternatives are added `match.one('one')` overwrites `.match('all')`
const schema = Joi.alternatives(Foo, Bar).match('all').concat(Joi.alternatives(Baz, Buz).match('one'))

// fails validation saying it matches too many
schema.validate({ foo: 'a', bar: 'b', baz: 'c' }) 

Edit:
I got the above case working by doing:

const Foo = Joi.object({ foo: Joi.string().required() }).unknown() 
const Bar = Joi.object({ bar: Joi.string().required() }).unknown() 
const Baz = Joi.object({ baz: Joi.string().required() }).unknown()
const Buz = Joi.object({ buz: Joi.string().required() }).unknown()
const FooAndBar = Joi.alternatives(Foo, Bar).match('all')
const BazOrBuz = Joi.alternatives(Baz,Buzz).match('one')
const schema = Joi.alternatives(FooAndBar, BazOrBuz).match('all')

So for the OP, the following should work:

const Foo = Joi.alternatives(Bar, Contents).match('all')