How to run error handling middleware on `validateSync()`?

[vkarpov15]

Right now we skip async validators on validateSync(), but the way we determine if a validator is async is based on the number of arguments. Since error handling middleware must take 3 arguments, validateSync() will never run error handling middleware #4885

Re: #4885

[hasezoey]

is this still a issue because doValidate uses isAsyncFunction which checks the function prototype instead of argument length?

[Uzlopak]

I think a unit test, which proves that the error handling middleware is called should prove that this issue is done.

[hasezoey]

i have opened up #12371 which address some of this issue

i have noticed that validateSync does not trigger any hooks, even if they are normal sync functions, so i made #12372 as a draft for now - if it is wanted that this function to not execute hooks, please close the PR (stating that)

PS: the documentation does not state that validateSync does not execute hooks, so it should maybe be mentioned if this is not a wanted feature (https://mongoosejs.com/docs/api.html#document_Document-validateSync)