[4.0] JSONEncoder conditional conformance workarounds #10818
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One of the limitations of not having conditional conformance at the moment is that the implementation of `init(from:)` and `encode(to:)` on types which require it is that failure to cast dependent types to `Encodable` or `Decodable` is a runtime failure. There is no way to statically guarantee that the wrapped type is `Encodable` or `Decodable`. As such, in those implementations, at best we can directly call `(element as! Encodable).encode(to: encoder)`, or similar. However, this encodes the element directly into an encoder, without giving the encoder a chance to intercept the type. This is problematic for `JSONEncoder` because it cannot apply a strategy if it doesn't get to intercept the type. This gives a temporary workaround for JSON strategies because of internal Foundation knowledge.
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@swift-ci Please test macOS |
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@swift-ci Please smoke test Linux |
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@swift-ci Please test Linux |
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What's in this pull request?
Cherry-picks #10766 to
swift-4.0-branch.Explanation: One of the limitations of not having conditional conformance at the moment is that the implementation of
init(from:)andencode(to:)on types which require it is that failure to cast dependent types toEncodableorDecodableis a runtime failure. There is no way to statically guarantee that the wrapped type isEncodableorDecodable.As such, in those implementations, at best we can directly call
(element as! Encodable).encode(to: encoder), or similar. However, this encodes the element directly into an encoder, without giving the encoder a chance to intercept the type. This is problematic forJSONEncoderbecause it cannot apply a strategy if it doesn't get to intercept the type.This gives a temporary workaround for JSON strategies because of internal Foundation knowledge.
Scope: Affects anyone encoding and decoding
Dates,Data,URLs, andDecimals withJSONEncoderandJSONDecoderRadar: rdar://problem/32535991
Risk: Low
Testing: Updates unit tests to confirm expected behavior.