Proposal Accepted
Thank you everyone for the very insightful feedback provided during this review. It provided some great insights into the Swift's community uses and desires on Codable.
Regarding the proposal itself, the Core Team has decided to accept it, with the proposal amended to include the details of the encoding format chosen. The data encoding chosen is an important semantic invariant of the API that is potentially observable by users and important for binary compatibility. Future proposals like this one that discuss adopting Codable should include details — and when necessary — rationale on the encoding chosen. Further, it would be valuable if the current chosen encodings for Standard Library types were also documented so that users using the default encodings for those types can either rely upon those encodings or know when they need to customize their encoding logic for a specific task.
In addition, the Core Team decided to extend the proposal to include Codable conformance for ContiguousArray, which was similarly missing from the Standard Library. This felt like a case that required no additional review discussion.
For Range types, the Core Team concluded from the review conversation that an unkeyed container representation seems like a reasonable default, but also recognized from the discussion on this thread that there are cases where a keyed representation is preferred. What this review thread further illustrated is the need to make Codable more flexible to provide the encoding customizations needed to service different tasks. There is no set of defaults for encoding that will satisfy every use-case. Some use-cases will prioritize serialization performance over human readability, and quite often the inverse. The Core Team would like to encourage the community to channel the energy that appeared in this thread to discussing general enhancements to Codeable to make it more flexible and amendable to serving more use-cases more easily, and @itaiferber has initiated a thread to do just that.
Thank you again for everyone who participated in this review!