fields with settings "required : undefined" are required #8219

Do you want to request a feature or report a bug?
I think this a bug.
If it is by design, I would be very curious as to why, as it seem misleading to me.

What is the current behavior?

if I create a schema like this

mongoose.Schema({name : {type : String, required : undefined}});

then the "name" field is required

also, if I set it like so

mongoose.Schema({name : {type : String, required : null}})

then the schema Throw with the error "Cannot read property 'message' of null

What is the expected behavior?
I would expect both a field marked with "required : undefined" or "required : null" to simply not be required, as their are falsy value and by default, if "required" is not set, it is "false".
this cause a subtle bug where if I have different biaviour depending if I have an object without the property "required" or if I have it but with value "undefined".

At most, I would expect that if we don't want for null and undefined value to be concidered as "falsy", we could throw a meaningfull message.

For null, the error is there because at schematype.js:791, there is the line if(typeof required === 'object'), letting pass the "null" value as it was an object.

For undefined, the error is because at schematype.js:797, there is the line if(required === false), not permitting undefined nor null.

do note, I don't know what to do if the value send is a string or number. Common sens would be probably to let normal javascript rules for coercion (so changing line 797 for if(!!required === false), and let a non-empty string or non-zero number be true, and an empty string or 0 be false.

What are the versions of Node.js, Mongoose and MongoDB you are using? Note that "latest" is not a version.

I use mongoose 5.7.2 and Node 11.7.0