On encode, we previously treated every container request as a push;
instead, we should allow the same container type to be requested
multiple times so a class can pass its Encoder directly to its
superclass if it needs to.
SingleValueDecondingContainers in JSON and Plist previously held the
assertion that attempting to decode an array or dictionary from them
was a type mismatch (since those represented unkeyed and keyed
containers, respectively). This assertion is no longer true, though,
since encode<T : Encodable>(_:) and decode<T : Decodable>(_:) allow
you to do just that.
This lifts the assertion and adds unit tests to both implementations to
ensure this works. (Addresses https://bugs.swift.org/browse/SR-5089)
* Adds conformance of Optional to Codable
* encode(...) arguments are no longer Optional; Optional values go
through generic version
* encodeIfPresent added to KeyedEncodingContainerProtocol to mirror
decodeIfPresent
* JSONEncoder and PropertyListEncoder updated to reflect these changes
codingPath more often than not actually needs to be copied, not just
referenced. This makes a big difference for nested containers and
subobjects, which were getting the wrong codingPath values when asking
for them.
This also adds unit tests for JSONEncoder and PropertyListEncoder to
confirm expected behavior.
* Integrate {JSON,PropertyList}{Encoder,Decoder} types to facilitate
encoding types in JSON and property list formats
* Adds Foundation-specific extensions to allow errors exposed from the
stdlib to bridge to NSErrors
