Wraps function types in additional brackets to prevent broken union types

[cmaster11]

E.g. take this schema:

export const AlternativesWithFunctionSchema = Joi.alternatives([
  Joi.function().minArity(2),
  Joi.object({
    json: Joi.any().required()
  }),
  Joi.object({
    raw: Joi.string().required()
  })
]).meta({ className: 'AlternativesWithFunctionInterface' });

Without brackets, a chain would have become

(...args: any[]) => any | {
  json: any;
} | {
  raw: string;
};

In this type, the whole any | { json: any; } | { raw: string; } is the return type of the function, which is wrong.

With brackets, it will be:

export type AlternativesWithFunctionInterface = ((...args: any[]) => any) | {
  json: any;
} | {
  raw: string;
};

There could be some more advanced logic to figure out if we want the brackets or not depending if we're using a union or not, but I feel it is even safer in general to just wrap function types in brackets given the "unsupported" nature of the Function type.

Note: this will conflict on merge with #401. I'll take care of it if merged. Probably one test will fail.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (e80f93f) 98.69% compared to head (f7c6bf9) 98.69%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #400   +/-   ##
=======================================
  Coverage   98.69%   98.69%           
=======================================
  Files           9        9           
  Lines         535      535           
  Branches      206      206           
=======================================
  Hits          528      528           
  Misses          7        7           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.