SwiftyJSON generates invalid JSON for inf/nan numbers

[kengruven]

What did you do?

JSON(Double.nan).rawString()

What did you expect to happen?

There's no way to serialize NaN (or Inf) in JSON, and rawString() returns an optional, so I expected to get nil.

What actually happened instead?

I got the Swift string "nan" (which is not valid JSON).

Environment

List the software versions you're using:

• SwiftyJSON: 5.0.0
• Xcode Version: 12.0.1 (12A7300)
• Swift Version: 5.3

Please also mention which package manager you used and its version.
other package managers in this list:

• Swift Package Manager Swift Package Manager - Swift 5.3.0

Project that demonstrates the issue

(It's literally one line of code, and it's shown above in full. If you really need a complete project, let me know and I'll see what I can do.)

[kengruven]

It looks like SwiftyJSON is simply returning the stringValue from NSNumber here, and that property obviously doesn't know anything about JSON syntax.

For comparison, when Foundation.JSONSerialization sees a Double.nan, it throws an NSInvalidArgumentException, "Invalid number value (NaN) in JSON write".