PostgreSQLError.stackTrace should be optional

[tonyarnold]

postgres-kit/Sources/PostgreSQL/Utilities/PostgreSQLError.swift

Line 28 in 561fa79

public var stackTrace: [String]

As per the original Core.Debuggable protocol, this property should return an optional type: https://github.com/vapor/core/blob/18f2436bf7a6bc2224372c0885db2e0159af1649/Sources/Debugging/Debuggable.swift#L31

I can't access the contents of this property in use, as the protocol has an extension method that returns nil with the correct optionality.

[tonyarnold]

Oh, I see: vapor/core#182

Well, this sucks.

[tanner0101]

@tonyarnold the PR you referenced there was trying to change the Debuggable protocol to have non-optional stack trace. That would definitely break things. But I think we can fix this issue in Postgres without making any breaking changes.

[tanner0101]

Actually no, Swift isn't letting me add a deprecation. I still think we should fix this, though. See my reasoning in #147.

[tonyarnold]

I think in a future release, making the stack trace property non-optional makes sense (you can always check if it's empty, right?). Thanks for looking into this, @tanner0101 - I appreciate your time and efforts.