What are you trying to achieve or the steps to reproduce ?

The .default method already supports providing a function value. I would like to expand the information returned by .describe() when the default is a function instead of a string.

const randomNumber = function () {
    return Math.random();
};
randomNumber.description = 'Generate random number';

const schema = Joi.any().default(randomNumber);
schema.validate(); // { error: null, value: 0.8081045034806544 }
schema.validate(); // { error: null, value: 0.42643964379927235 }

Which result you had ?

Using the above schema:

schema.describe();
/*
{ type: 'any', flags: { default: 'Generate random number' } }
*/

What did you expect ?

I would like to add details so that describe instead returns:

schema.describe();
/*
{ type: 'any', flags: { default: {
    description: 'Generate random number',
    function: randomNumber
} } }
*/

This would allow for this contrived example to work:

schema.describe().flags.default.function(); // 0.6658680107310528

(Full disclosure, I would like to allow for dynamic defaults in Felicity, which is built upon .describe())

Any feedback on this would be appreciated, and I'm 100% willing to add this support if approved.