Decode the `Codable` value or set it to `nil

DecodeOrNil.swift

/// Attempt to decode value or return `nil`
///
/// Example:
/// ```
/// struct User {
///   @DecodeOrNil var avatarURL: URL?  // Sets it to nil if server sends an invalid URL for avatarURL.
/// }
/// ```
@propertyWrapper
public struct DecodeOrNil<T: Codable>: Codable {
  public var wrappedValue: T?

  public init(wrappedValue: T?) {
    self.wrappedValue = wrappedValue
  }

  public init(from decoder: Decoder) throws {
    let container = try decoder.singleValueContainer()
    wrappedValue = try? container.decode(T.self)
  }

  public func encode(to encoder: Encoder) throws {
    try wrappedValue.encode(to: encoder)
  }
}

extension DecodeOrNil: Equatable where T: Equatable {}
extension DecodeOrNil: Hashable where T: Hashable {}