Create a joi decorator function that dinamycali extend the validations.

joiDecorate.js

//Include joi module schema validator.
const Joi = require('joi');

/*
	Receive a js structure using joi values and return it as a joi object with keys.
	Params:
		schema : {strucutre}
	Returns:
		{Joi object}
*/
const base = (schema) => Joi.object().keys(schema);


/*
	Receive a joi schema object and add unknow property to allow fields don't declared in the schema.
	Params:
		schema : {Joi object}
	Returns:
		{Joi object}
*/
const unknown = (schema) => schema.unknown(true);

/*
	Receive a joi object - keys and return the key list.
	Params:
		schema : {Joi object}
	Returns:
		[string]
*/
const getKeys = (schema) => (schema&&schema._inner.children) 
	? schema._inner.children.map(elem => elem.key) 
	: [];

/*
	Receive a joi schema that add a 'or' validation, allow one or more field of the structure.
	Params:
		schema : {Joi object}
	Returns:
		{Joi object}
*/
const partial = (schema) => schema.or(getKeys(schema));

/*
	Receive a joi schema that add a 'and' validation, allow all the field of the structure in the param.
	Params:
		schema : {Joi object}
	Returns:
		{Joi object}
*/
const mandatory = (schema) => schema.with(getKeys(schema));


/*
	Validate a joi structure and return a promise.
	Params:
		schema : {Joi object}
		myObj  : {js flat structure}
	Returns:
		promise
*/
const validate = async (myObj,schema)=> await Joi.validate(myObj, schema);

/*
	Create a partial validation and validate it.
	Params:
		schema : {Joi object}
		Obj : {js flat structure}
	Returns:
		promise
*/
const partialValidation = (obj,schema) => validate(obj,unknown(partial(schema)));

/*
	Create a complete validation and validate it.
	Params:
		schema : {Joi object}
		Obj : {js flat structure}
	Returns:
		promise
*/
const completeValidation = (obj,schema) => validate(obj,unknown(partial(schema)));

/* -------------------
				EXAMPLE
  -------------------- */

//Define a custom schema.
let schema =  Joi.object().keys({
	username : Joi.string().alphanum(),
	password : Joi.string().regex(/^[a-zA-Z0-9]{6,16}$/).min(6),
	dni: Joi.number(),
	single: Joi.boolean(),
	email:Joi.string().email(),
	cbu:Joi.string()
});

const peter = {	
	opa:'aaa',
	sex:true,
	dni:33295515
};

partialValidation(peter,schema)
	.then((ok)=>console.log('ok PARTIAL'))
	.catch((err)=>console.log('error>>',err));

completeValidation(peter,schema)
	.then((ok)=>console.log('ok COMPLETE'))
	.catch((err)=>console.log('error>>',err));