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Merged
merged 5 commits into from
Sep 30, 2025
+59 −3
Merged

Improve performance of JSONDecoder and JSONEncoder for large apps #1481

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1152aa4
Improve performance of JSONDecoder and JSONEncoder for large apps
ChrisBenua Aug 27, 2025
38659e6
use switch instead of casting to protocol
ChrisBenua Sep 15, 2025
45a07ab
replace as with specializingCast
ChrisBenua Sep 16, 2025
a0f84ef
fix styling and remove extra diff
ChrisBenua Sep 23, 2025
b278932
make extensions fileprivate
ChrisBenua Sep 23, 2025
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11 changes: 10 additions & 1 deletion Sources/FoundationEssentials/JSON/JSONDecoder.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -610,7 +610,7 @@ extension JSONDecoderImpl: Decoder {
if type == Decimal.self {
return try self.unwrapDecimal(from: mapValue, for: codingPathNode, additionalKey) as! T
}
if T.self is _JSONStringDictionaryDecodableMarker.Type {
if !options.keyDecodingStrategy.isDefault, T.self is _JSONStringDictionaryDecodableMarker.Type {
return try self.unwrapDictionary(from: mapValue, as: type, for: codingPathNode, additionalKey)
}

Expand Down Expand Up @@ -1857,5 +1857,14 @@ extension EncodingError {
}
}

fileprivate extension JSONDecoder.KeyDecodingStrategy {
var isDefault: Bool {
switch self {
case .useDefaultKeys: true
default: false
}
}
}

@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
extension JSONDecoder : @unchecked Sendable {}
51 changes: 49 additions & 2 deletions Sources/FoundationEssentials/JSON/JSONEncoder.swift
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Expand Up @@ -1214,9 +1214,9 @@ private extension __JSONEncoder {
return self.wrap(url.absoluteString)
} else if let decimal = value as? Decimal {
return .number(decimal.description)
} else if let encodable = value as? _JSONStringDictionaryEncodableMarker {
} else if !options.keyEncodingStrategy.isDefault, let encodable = value as? _JSONStringDictionaryEncodableMarker {
return try self.wrap(encodable as! [String:Encodable], for: additionalKey)
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Are we able to use _specializingCast here as well?

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Unfortunately, no, we can't use it here. _specializingCast internally performs type equality check, and here we use as? to check protocol conformance. so _specializingCast is inapplicable here

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@ChrisBenua ChrisBenua Sep 30, 2025 •
edited
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@inline(__always)
internal func _specializingCast<Input, Output>(_ value: Input, to type: Output.Type) -> Output? {
  guard Input.self == Output.self else { return nil } // this check will always fail when we check for protocol conformance
  return _identityCast(value, to: type)
}

} else if let array = value as? _JSONDirectArrayEncodable {
} else if let array = _asDirectArrayEncodable(value, for: additionalKey) {
if options.outputFormatting.contains(.prettyPrinted) {
let (bytes, lengths) = try array.individualElementRepresentation(encoder: self, additionalKey)
return .directArray(bytes, lengths: lengths)
Expand Down Expand Up @@ -1246,6 +1246,42 @@ private extension __JSONEncoder {
return encoder.takeValue()
}

func _asDirectArrayEncodable<T: Encodable>(_ value: T, for additionalKey: (some CodingKey)? = _CodingKey?.none) -> _JSONDirectArrayEncodable? {
return if let array = _specializingCast(array, to: [Int8].self) {
array
} else if let array = _specializingCast(array, to: [Int16].self) {
array
} else if let array = _specializingCast(array, to: [Int32].self) {
array
} else if let array = _specializingCast(array, to: [Int64].self) {
array
} else if let array = _specializingCast(array, to: [Int128].self) {
array
} else if let array = _specializingCast(array, to: [Int].self) {
array
} else if let array = _specializingCast(array, to: [UInt8].self) {
array
} else if let array = _specializingCast(array, to: [UInt16].self) {
array
} else if let array = _specializingCast(array, to: [UInt32].self) {
array
} else if let array = _specializingCast(array, to: [UInt64].self) {
array
} else if let array = _specializingCast(array, to: [UInt128].self) {
array
} else if let array = _specializingCast(array, to: [UInt].self) {
array
} else if let array = _specializingCast(array, to: [String].self) {
array
} else if let array = _specializingCast(array, to: [Float].self) {
array
} else if let array = _specializingCast(array, to: [Double].self) {
array
} else {
nil
}
}

@inline(__always)
func getEncoder(for additionalKey: CodingKey?) -> __JSONEncoder {
if let additionalKey {
Expand Down Expand Up @@ -1466,3 +1502,14 @@ extension Array : _JSONDirectArrayEncodable where Element: _JSONSimpleValueArray
return (writer.bytes, lengths: byteLengths)
}
}

fileprivate extension JSONEncoder.KeyEncodingStrategy {
var isDefault: Bool {
switch self {
case .useDefaultKeys:
return true
case .custom, .convertToSnakeCase:
return false
}
}
}