Restructure files a bit. Make Date handling relatively robust compared to my first pass at it. Make the failure to construct a generic open API node type throw an error rather than silently omit the node.

Sources/JSONAPIOpenAPI/OpenAPI/Date+OpenAPI.swift

@@ -0,0 +1,40 @@
+//
+//  Date+OpenAPI.swift
+//  JSONAPIOpenAPI
+//
+//  Created by Mathew Polzin on 1/24/19.
+//
+
+import Foundation
+
+extension Date: DateOpenAPINodeType {
+	public static func dateOpenAPINodeGuess(using encoder: JSONEncoder) -> JSONNode? {
+
+		switch encoder.dateEncodingStrategy {
+		case .deferredToDate, .custom:
+			// I don't know if we can say anything about this case without
+			// encoding the Date and looking at it, which is what `primitiveGuess()`
+			// does.
+			return nil
+
+		case .secondsSince1970,
+			 .millisecondsSince1970:
+			return .number(.init(format: .double,
+								 required: true),
+						   .init())
+
+		case .iso8601:
+			return .string(.init(format: .dateTime,
+								 required: true),
+						   .init())
+
+		case .formatted(let formatter):
+			let hasTime = formatter.timeStyle != .none
+			let format: JSONTypeFormat.StringFormat = hasTime ? .dateTime : .date
+
+			return .string(.init(format: format,
+								 required: true),
+						   .init())
+		}
+	}
+}

Sources/JSONAPIOpenAPI/OpenAPI/OpenAPITypes.swift

@@ -74,6 +74,12 @@ public protocol GenericOpenAPINodeType {
 	static func genericOpenAPINode(using encoder: JSONEncoder) throws -> JSONNode
 }
 
+/// Anything conforming to `DateOpenAPINodeType` is
+/// able to attempt to represent itself as a date OpenAPINode
+public protocol DateOpenAPINodeType {
+	static func dateOpenAPINodeGuess(using encoder: JSONEncoder) -> JSONNode?
+}
+
 /// Anything conforming to `AnyJSONCaseIterable` can provide a
 /// list of its possible values.
 public protocol AnyJSONCaseIterable {
@@ -603,6 +609,7 @@ public enum OpenAPICodableError: Swift.Error, Equatable {
 	case primitiveGuessFailed
 }
 
-public enum OpenAPITypeError: Swift.Error, Equatable {
+public enum OpenAPITypeError: Swift.Error {
 	case invalidNode
+	case unknownNodeType(Any.Type)
 }