merge w/ master

JSONAPI.playground/Pages/Full Client & Server Example.xcplaygroundpage/Contents.swift

@@ -1,5 +1,6 @@
 import Foundation
 import JSONAPI
+import Poly
 
 // MARK: - Preamble (setup)
 

JSONAPI.playground/Pages/OpenAPI Documentation.xcplaygroundpage/Contents.swift

@@ -16,14 +16,14 @@ print("====")
 print(personSchemaData.map { String(data: $0, encoding: .utf8)! } ?? "Schema Construction Failed")
 print("====")
 
-let dogDocumentSchemaData = try? encoder.encode(SingleDogDocument.openAPINodeWithExample())
+let dogDocumentSchemaData = try? encoder.encode(SingleDogDocument.openAPINodeWithExample(using: encoder))
 
 print("Dog Document Schema")
 print("====")
 print(dogDocumentSchemaData.map { String(data: $0, encoding: .utf8)! } ?? "Schema Construction Failed")
 print("====")
 
-let batchPersonSchemaData = try? encoder.encode(BatchPeopleDocument.openAPINodeWithExample())
+let batchPersonSchemaData = try? encoder.encode(BatchPeopleDocument.openAPINodeWithExample(using: encoder))
 
 print("Batch Person Document Schema")
 print("====")

Package.resolved

@@ -23,9 +23,9 @@
         "package": "Poly",
         "repositoryURL": "https://github.com/mattpolzin/Poly.git",
         "state": {
-          "branch": "master",
+          "branch": null,
           "revision": "77f45b8963a51c02d71fc4075eba5cff47ff0d07",
-          "version": null
+          "version": "1.0.0"
         }
       },
       {

Package.swift

@@ -20,7 +20,7 @@ let package = Package(
             targets: ["JSONAPIOpenAPI"])
     ],
     dependencies: [
-		.package(url: "https://github.com/mattpolzin/Poly.git", .branch("master")),
+		.package(url: "https://github.com/mattpolzin/Poly.git", from: "1.0.0"),
         .package(url: "https://github.com/Flight-School/AnyCodable.git", from: "0.1.0"),
 		.package(url: "https://github.com/typelift/SwiftCheck.git", from: "0.11.0")
     ],

Sources/JSONAPIOpenAPI/JSONAPI/JSONAPIInclude+OpenAPI.swift

@@ -6,6 +6,7 @@
 //
 
 import JSONAPI
+import Foundation
 
 extension Includes: OpenAPINodeType where I: OpenAPINodeType {
 	public static func openAPINode() throws -> JSONNode {

Sources/JSONAPIOpenAPI/JSONAPI/JSONAPITypes+OpenAPI.swift

@@ -6,11 +6,17 @@
 //
 
 import JSONAPI
+import Foundation
 import AnyCodable
 
 private protocol _Optional {}
 extension Optional: _Optional {}
 
+private protocol Wrapper {
+	associatedtype Wrapped
+}
+extension Optional: Wrapper {}
+
 extension Attribute: OpenAPINodeType where RawValue: OpenAPINodeType {
 	static public func openAPINode() throws -> JSONNode {
 		// If the RawValue is not required, we actually consider it
@@ -48,14 +54,26 @@ extension Attribute: WrappedRawOpenAPIType where RawValue: RawOpenAPINodeType {
 }
 
 extension Attribute: AnyJSONCaseIterable where RawValue: CaseIterable, RawValue: Codable {
-	public static var allCases: [AnyCodable] {
-		return (try? allCases(from: Array(RawValue.allCases))) ?? []
+	public static func allCases(using encoder: JSONEncoder) -> [AnyCodable] {
+		return (try? allCases(from: Array(RawValue.allCases), using: encoder)) ?? []
 	}
 }
 
 extension Attribute: AnyWrappedJSONCaseIterable where RawValue: AnyJSONCaseIterable {
-	public static var allCases: [AnyCodable] {
-		return RawValue.allCases
+	public static func allCases(using encoder: JSONEncoder) -> [AnyCodable] {
+		return RawValue.allCases(using: encoder)
+	}
+}
+
+extension Attribute: GenericOpenAPINodeType where RawValue: GenericOpenAPINodeType {
+	public static func genericOpenAPINode(using encoder: JSONEncoder) throws -> JSONNode {
+		return try RawValue.genericOpenAPINode(using: encoder)
+	}
+}
+
+extension Attribute: DateOpenAPINodeType where RawValue: DateOpenAPINodeType {
+	public static func dateOpenAPINodeGuess(using encoder: JSONEncoder) -> JSONNode? {
+		return RawValue.dateOpenAPINodeGuess(using: encoder)
 	}
 }
 
@@ -71,6 +89,8 @@ extension TransformedAttribute: OpenAPINodeType where RawValue: OpenAPINodeType
 	}
 }
 
+// TODO: conform TransformedAttribute to all of the above protocols that Attribute conforms to.
+
 extension RelationshipType {
 	static func relationshipNode(nullable: Bool, jsonType: String) -> JSONNode {
 		let propertiesDict: [String: JSONNode] = [
@@ -121,8 +141,8 @@ extension ToManyRelationship: OpenAPINodeType {
 	}
 }
 
-extension Entity: OpenAPINodeType where Description.Attributes: Sampleable, Description.Relationships: Sampleable {
-	public static func openAPINode() throws -> JSONNode {
+extension Entity: OpenAPIEncodedNodeType where Description.Attributes: Sampleable, Description.Relationships: Sampleable {
+	public static func openAPINode(using encoder: JSONEncoder) throws -> JSONNode {
 		// NOTE: const for json `type` not supported by OpenAPI 3.0
 		//		Will use "enum" with one possible value for now.
 
@@ -141,13 +161,13 @@ extension Entity: OpenAPINodeType where Description.Attributes: Sampleable, Desc
 
 		let attributesNode: JSONNode? = Description.Attributes.self == NoAttributes.self
 			? nil
-			: try Description.Attributes.genericObjectOpenAPINode()
+			: try Description.Attributes.genericOpenAPINode(using: encoder)
 
 		let attributesProperty = attributesNode.map { ("attributes", $0) }
 
 		let relationshipsNode: JSONNode? = Description.Relationships.self == NoRelationships.self
 			? nil
-			: try Description.Relationships.genericObjectOpenAPINode()
+			: try Description.Relationships.genericOpenAPINode(using: encoder)
 
 		let relationshipsProperty = relationshipsNode.map { ("relationships", $0) }
 
@@ -164,26 +184,26 @@ extension Entity: OpenAPINodeType where Description.Attributes: Sampleable, Desc
 	}
 }
 
-extension SingleResourceBody: OpenAPINodeType where Entity: OpenAPINodeType {
-	public static func openAPINode() throws -> JSONNode {
-		return try Entity.openAPINode()
+extension SingleResourceBody: OpenAPIEncodedNodeType where Entity: OpenAPIEncodedNodeType {
+	public static func openAPINode(using encoder: JSONEncoder) throws -> JSONNode {
+		return try Entity.openAPINode(using: encoder)
 	}
 }
 
-extension ManyResourceBody: OpenAPINodeType where Entity: OpenAPINodeType {
-	public static func openAPINode() throws -> JSONNode {
+extension ManyResourceBody: OpenAPIEncodedNodeType where Entity: OpenAPIEncodedNodeType {
+	public static func openAPINode(using encoder: JSONEncoder) throws -> JSONNode {
 		return .array(.init(format: .generic,
 							required: true),
-					  .init(items: try Entity.openAPINode()))
+					  .init(items: try Entity.openAPINode(using: encoder)))
 	}
 }
 
-extension Document: OpenAPINodeType where PrimaryResourceBody: OpenAPINodeType, IncludeType: OpenAPINodeType {
-	public static func openAPINode() throws -> JSONNode {
+extension Document: OpenAPIEncodedNodeType where PrimaryResourceBody: OpenAPIEncodedNodeType, IncludeType: OpenAPINodeType {
+	public static func openAPINode(using encoder: JSONEncoder) throws -> JSONNode {
 		// TODO: metadata, links, api description, errors
 		// TODO: represent data and errors as the two distinct possible outcomes
 
-		let primaryDataNode: JSONNode? = try PrimaryResourceBody.openAPINode()
+		let primaryDataNode: JSONNode? = try PrimaryResourceBody.openAPINode(using: encoder)
 
 		let primaryDataProperty = primaryDataNode.map { ("data", $0) }
 
@@ -191,7 +211,7 @@ extension Document: OpenAPINodeType where PrimaryResourceBody: OpenAPINodeType,
 		do {
 			includeNode = try Includes<Include>.openAPINode()
 		} catch let err as OpenAPITypeError {
-			guard err == .invalidNode else {
+			guard case .invalidNode = err else {
 				throw err
 			}
 			includeNode = nil

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

@@ -17,9 +17,16 @@ public protocol OpenAPINodeType {
 	static func openAPINode() throws -> JSONNode
 }
 
-extension OpenAPINodeType where Self: Sampleable, Self: Encodable {
-	public static func openAPINodeWithExample() throws -> JSONNode {
-		return try openAPINode().with(example: Self.successSample ?? Self.sample)
+/// Anything conforming to `OpenAPIEncodedNodeType` can provide an
+/// OpenAPI schema representing itself but it may need an Encoder
+/// to do its job.
+public protocol OpenAPIEncodedNodeType {
+	static func openAPINode(using encoder: JSONEncoder) throws -> JSONNode
+}
+
+extension OpenAPIEncodedNodeType where Self: Sampleable, Self: Encodable {
+	public static func openAPINodeWithExample(using encoder: JSONEncoder = JSONEncoder()) throws -> JSONNode {
+		return try openAPINode(using: encoder).with(example: Self.successSample ?? Self.sample, using: encoder)
 	}
 }
 
@@ -56,15 +63,27 @@ public protocol DoubleWrappedRawOpenAPIType {
 	static func wrappedOpenAPINode() throws -> JSONNode
 }
 
+/// A GenericOpenAPINodeType can take a stab at
+/// determining its OpenAPINode because it is sampleable.
+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 {
-	static var allCases: [AnyCodable] { get }
+	static func allCases(using encoder: JSONEncoder) -> [AnyCodable]
 }
 
 extension AnyJSONCaseIterable {
 	/// Given an array of Codable values, retrieve an array of AnyCodables.
-	static func allCases<T: Codable>(from input: [T]) throws -> [AnyCodable] {
+	static func allCases<T: Codable>(from input: [T], using encoder: JSONEncoder) throws -> [AnyCodable] {
 		if let alreadyGoodToGo = input as? [AnyCodable] {
 			return alreadyGoodToGo
 		}
@@ -77,7 +96,7 @@ extension AnyJSONCaseIterable {
 		// by AnyCodable, but AnyCodable wants it to actually BE a String
 		// upon initialization.
 
-		guard let arrayOfCodables = try JSONSerialization.jsonObject(with: JSONEncoder().encode(input), options: []) as? [Any] else {
+		guard let arrayOfCodables = try JSONSerialization.jsonObject(with: encoder.encode(input), options: []) as? [Any] else {
 			throw OpenAPICodableError.allCasesArrayNotCodable
 		}
 		return arrayOfCodables.map(AnyCodable.init)
@@ -92,7 +111,7 @@ extension AnyJSONCaseIterable {
 /// The "different" conditions have to do
 /// with Optionality, hence the name of this protocol.
 public protocol AnyWrappedJSONCaseIterable {
-	static var allCases: [AnyCodable] { get }
+	static func allCases(using encoder: JSONEncoder) -> [AnyCodable]
 }
 
 public protocol SwiftTyped {
@@ -284,14 +303,14 @@ public enum JSONNode: Equatable {
 					nullable: Bool = false,
 //					constantValue: Format.SwiftType? = nil,
 					allowedValues: [AnyCodable]? = nil,
-					example: AnyCodable? = nil) {
+					example: (codable: AnyCodable, encoder: JSONEncoder)? = nil) {
 			self.format = format
 			self.required = required
 			self.nullable = nullable
 //			self.constantValue = constantValue
 			self.allowedValues = allowedValues
 			self.example = example
-				.flatMap { try? JSONEncoder().encode($0)}
+				.flatMap { try? $0.encoder.encode($0.codable)}
 				.flatMap { String(data: $0, encoding: .utf8) }
 		}
 
@@ -332,13 +351,13 @@ public enum JSONNode: Equatable {
 		}
 
 		/// Return this context with the given example
-		public func with(example: AnyCodable) -> Context {
+		public func with(example: AnyCodable, using encoder: JSONEncoder) -> Context {
 			return .init(format: format,
 						 required: required,
 						 nullable: nullable,
 //						 constantValue: constantValue,
 						 allowedValues: allowedValues,
-						 example: example)
+						 example: (codable: example, encoder: encoder))
 		}
 	}
 
@@ -552,27 +571,28 @@ public enum JSONNode: Equatable {
 		}
 	}
 
-	public func with<T: Encodable>(example codableExample: T) throws -> JSONNode {
+	public func with<T: Encodable>(example codableExample: T,
+								   using encoder: JSONEncoder) throws -> JSONNode {
 		let example: AnyCodable
 		if let goodToGo = codableExample as? AnyCodable {
 			example = goodToGo
 		} else {
-			example = AnyCodable(try JSONSerialization.jsonObject(with: JSONEncoder().encode(codableExample), options: []))
+			example = AnyCodable(try JSONSerialization.jsonObject(with: encoder.encode(codableExample), options: []))
 		}
 
 		switch self {
 		case .boolean(let context):
-			return .boolean(context.with(example: example))
+			return .boolean(context.with(example: example, using: encoder))
 		case .object(let contextA, let contextB):
-			return .object(contextA.with(example: example), contextB)
+			return .object(contextA.with(example: example, using: encoder), contextB)
 		case .array(let contextA, let contextB):
-			return .array(contextA.with(example: example), contextB)
+			return .array(contextA.with(example: example, using: encoder), contextB)
 		case .number(let context, let contextB):
-			return .number(context.with(example: example), contextB)
+			return .number(context.with(example: example, using: encoder), contextB)
 		case .integer(let context, let contextB):
-			return .integer(context.with(example: example), contextB)
+			return .integer(context.with(example: example, using: encoder), contextB)
 		case .string(let context, let contextB):
-			return .string(context.with(example: example), contextB)
+			return .string(context.with(example: example, using: encoder), contextB)
 		case .all, .one, .any, .not, .reference:
 			return self
 		}
@@ -582,10 +602,12 @@ public enum JSONNode: Equatable {
 public enum OpenAPICodableError: Swift.Error, Equatable {
 	case allCasesArrayNotCodable
 	case exampleNotCodable
+	case primitiveGuessFailed
 }
 
-public enum OpenAPITypeError: Swift.Error, Equatable {
+public enum OpenAPITypeError: Swift.Error {
 	case invalidNode
+	case unknownNodeType(Any.Type)
 }
 
 /// Anything conforming to RefName knows what to call itself

Sources/JSONAPIOpenAPI/OpenAPI/SwiftPrimitiveTypes+OpenAPI.swift

@@ -6,6 +6,7 @@
 //
 
 import AnyCodable
+import Foundation
 
 /**
 
@@ -56,8 +57,8 @@ extension Optional: DoubleWrappedRawOpenAPIType where Wrapped: WrappedRawOpenAPI
 }
 
 extension Optional: AnyJSONCaseIterable where Wrapped: CaseIterable, Wrapped: Codable {
-	public static var allCases: [AnyCodable] {
-		return (try? allCases(from: Array(Wrapped.allCases))) ?? []
+	public static func allCases(using encoder: JSONEncoder) -> [AnyCodable] {
+		return (try? allCases(from: Array(Wrapped.allCases), using: encoder)) ?? []
 	}
 }
 

Sources/JSONAPIOpenAPI/Sampleable.swift

@@ -1,116 +0,0 @@
-//
-//  Sampleable.swift
-//  JSONAPIOpenAPI
-//
-//  Created by Mathew Polzin on 1/15/19.
-//
-
-import JSONAPI
-import AnyCodable
-
-/// A Sampleable type can provide a sample value.
-/// This is useful for reflection.
-public protocol Sampleable {
-	/// Get a sample value of type Self. This can be the
-	/// same value every time, or it can be an arbitrarily random
-	/// value each time.
-	static var sample: Self { get }
-
-	/// Get an example of success, if that is meaningful and
-	/// available. If not, will be nil.
-	static var successSample: Self? { get }
-
-	/// Get an example of failure, if that is meaningful and
-	/// available. If not, will be nil.
-	static var failureSample: Self? { get }
-}
-
-public extension Sampleable {
-	public static var successSample: Self? { return nil }
-
-	public static var failureSample: Self? { return nil }
-}
-
-extension Sampleable {
-	public static func genericObjectOpenAPINode() throws -> JSONNode {
-		let mirror = Mirror(reflecting: Self.sample)
-		let properties: [(String, JSONNode)] = try mirror.children.compactMap { child in
-
-			// see if we can enumerate the possible values
-			let maybeAllCases: [AnyCodable]? = {
-				switch type(of: child.value) {
-				case let valType as AnyJSONCaseIterable.Type:
-					return valType.allCases
-				case let valType as AnyWrappedJSONCaseIterable.Type:
-					return valType.allCases
-				default:
-					return nil
-				}
-			}()
-
-			// try to snag an OpenAPI Node
-			let maybeOpenAPINode: JSONNode? = try {
-				switch type(of: child.value) {
-				case let valType as OpenAPINodeType.Type:
-					return try valType.openAPINode()
-
-				case let valType as RawOpenAPINodeType.Type:
-					return try valType.rawOpenAPINode()
-
-				case let valType as WrappedRawOpenAPIType.Type:
-					return try valType.wrappedOpenAPINode()
-
-				case let valType as DoubleWrappedRawOpenAPIType.Type:
-					return try valType.wrappedOpenAPINode()
-
-				default:
-					return nil
-				}
-			}()
-
-			// put it all together
-			let newNode: JSONNode?
-			if let allCases = maybeAllCases,
-				let openAPINode = maybeOpenAPINode {
-				newNode = try openAPINode.with(allowedValues: allCases)
-			} else {
-				newNode = maybeOpenAPINode
-			}
-
-			return zip(child.label, newNode) { ($0, $1) }
-		}
-
-		// There should not be any duplication of keys since these are
-		// property names, but rather than risk runtime exception, we just
-		// fail to the newer value arbitrarily
-		let propertiesDict = Dictionary(properties) { _, value2 in value2 }
-
-		return .object(.init(format: .generic,
-							 required: true),
-					   .init(properties: propertiesDict))
-	}
-}
-
-extension NoAttributes: Sampleable {
-	public static var sample: NoAttributes {
-		return .none
-	}
-}
-
-extension NoRelationships: Sampleable {
-	public static var sample: NoRelationships {
-		return .none
-	}
-}
-
-extension NoMetadata: Sampleable {
-	public static var sample: NoMetadata {
-		return .none
-	}
-}
-
-extension NoLinks: Sampleable {
-	public static var sample: NoLinks {
-		return .none
-	}
-}

Sources/JSONAPIOpenAPI/Sampleable/Include+Sampleable.swift

@@ -0,0 +1,184 @@
+//
+//  Include+Sampleable.swift
+//  JSONAPIOpenAPI
+//
+//  Created by Mathew Polzin on 1/23/19.
+//
+
+import JSONAPI
+
+extension Includes: Sampleable where I: Sampleable {
+	public static var sample: Includes<I> {
+		guard I.self != NoIncludes.self else {
+			return .none
+		}
+
+		return .init(values: I.samples)
+	}
+}
+
+extension NoIncludes: Sampleable {
+	public static var sample: NoIncludes {
+		return NoIncludes()
+	}
+}
+
+extension Include1: Sampleable where A: Sampleable {
+	public static var sample: Include1<A> {
+		return .init(A.sample)
+	}
+
+	public static var samples: [Include1<A>] {
+		return A.samples.map(Include1<A>.init)
+	}
+}
+
+extension Include2: Sampleable where A: Sampleable, B: Sampleable {
+	public static var sample: Include2<A, B> {
+		let randomChoice = Int.random(in: 0..<samples.count)
+
+		return samples[randomChoice]
+	}
+
+	public static var samples: [Include2<A, B>] {
+		return A.samples.map(Include2<A, B>.init)
+			+ B.samples.map(Include2<A, B>.init)
+	}
+}
+
+extension Include3: Sampleable where A: Sampleable, B: Sampleable, C: Sampleable {
+	public static var sample: Include3<A, B, C> {
+		let randomChoice = Int.random(in: 0..<samples.count)
+
+		return samples[randomChoice]
+	}
+
+	public static var samples: [Include3<A, B, C>] {
+		return A.samples.map(Include3<A, B, C>.init)
+			+ B.samples.map(Include3<A, B, C>.init)
+			+ C.samples.map(Include3<A, B, C>.init)
+	}
+}
+
+extension Include4: Sampleable where A: Sampleable, B: Sampleable, C: Sampleable, D: Sampleable {
+	public static var sample: Include4<A, B, C, D> {
+		let randomChoice = Int.random(in: 0..<samples.count)
+
+		return samples[randomChoice]
+	}
+
+	public static var samples: [Include4<A, B, C, D>] {
+		return A.samples.map(Include4<A, B, C, D>.init)
+			+ B.samples.map(Include4<A, B, C, D>.init)
+			+ C.samples.map(Include4<A, B, C, D>.init)
+			+ D.samples.map(Include4<A, B, C, D>.init)
+	}
+}
+
+extension Include5: Sampleable where A: Sampleable, B: Sampleable, C: Sampleable, D: Sampleable, E: Sampleable {
+	public static var sample: Include5<A, B, C, D, E> {
+		let randomChoice = Int.random(in: 0..<samples.count)
+
+		return samples[randomChoice]
+	}
+
+	public static var samples: [Include5<A, B, C, D, E>] {
+		let set1: [Include5<A, B, C, D, E>] = A.samples.map(Include5<A, B, C, D, E>.init)
+			+ B.samples.map(Include5<A, B, C, D, E>.init)
+			+ C.samples.map(Include5<A, B, C, D, E>.init)
+
+		let set2: [Include5<A, B, C, D, E>] = D.samples.map(Include5<A, B, C, D, E>.init)
+			+ E.samples.map(Include5<A, B, C, D, E>.init)
+
+		return set1 + set2
+	}
+}
+
+extension Include6: Sampleable where A: Sampleable, B: Sampleable, C: Sampleable, D: Sampleable, E: Sampleable, F: Sampleable {
+	public static var sample: Include6<A, B, C, D, E, F> {
+		let randomChoice = Int.random(in: 0..<samples.count)
+
+		return samples[randomChoice]
+	}
+
+	public static var samples: [Include6<A, B, C, D, E, F>] {
+		let set1: [Include6<A, B, C, D, E, F>] = A.samples.map(Include6<A, B, C, D, E, F>.init)
+			+ B.samples.map(Include6<A, B, C, D, E, F>.init)
+			+ C.samples.map(Include6<A, B, C, D, E, F>.init)
+
+		let set2: [Include6<A, B, C, D, E, F>] = D.samples.map(Include6<A, B, C, D, E, F>.init)
+			+ E.samples.map(Include6<A, B, C, D, E, F>.init)
+			+ F.samples.map(Include6<A, B, C, D, E, F>.init)
+
+		return set1 + set2
+	}
+}
+
+extension Include7: Sampleable where A: Sampleable, B: Sampleable, C: Sampleable, D: Sampleable, E: Sampleable, F: Sampleable, G: Sampleable {
+	public static var sample: Include7<A, B, C, D, E, F, G> {
+		let randomChoice = Int.random(in: 0..<samples.count)
+
+		return samples[randomChoice]
+	}
+
+	public static var samples: [Include7<A, B, C, D, E, F, G>] {
+		let set1: [Include7<A, B, C, D, E, F, G>] = A.samples.map(Include7<A, B, C, D, E, F, G>.init)
+			+ B.samples.map(Include7<A, B, C, D, E, F, G>.init)
+			+ C.samples.map(Include7<A, B, C, D, E, F, G>.init)
+
+		let set2: [Include7<A, B, C, D, E, F, G>] = D.samples.map(Include7<A, B, C, D, E, F, G>.init)
+			+ E.samples.map(Include7<A, B, C, D, E, F, G>.init)
+			+ F.samples.map(Include7<A, B, C, D, E, F, G>.init)
+
+		let set3: [Include7<A, B, C, D, E, F, G>] = G.samples.map(Include7<A, B, C, D, E, F, G>.init)
+
+		return set1 + set2 + set3
+	}
+}
+
+extension Include8: Sampleable where A: Sampleable, B: Sampleable, C: Sampleable, D: Sampleable, E: Sampleable, F: Sampleable, G: Sampleable, H: Sampleable {
+	public static var sample: Include8<A, B, C, D, E, F, G, H> {
+		let randomChoice = Int.random(in: 0..<samples.count)
+
+		return samples[randomChoice]
+	}
+
+	public static var samples: [Include8<A, B, C, D, E, F, G, H>] {
+		let set1: [Include8<A, B, C, D, E, F, G, H>] = A.samples.map(Include8<A, B, C, D, E, F, G, H>.init)
+			+ B.samples.map(Include8<A, B, C, D, E, F, G, H>.init)
+			+ C.samples.map(Include8<A, B, C, D, E, F, G, H>.init)
+
+		let set2: [Include8<A, B, C, D, E, F, G, H>] = D.samples.map(Include8<A, B, C, D, E, F, G, H>.init)
+			+ E.samples.map(Include8<A, B, C, D, E, F, G, H>.init)
+			+ F.samples.map(Include8<A, B, C, D, E, F, G, H>.init)
+
+		let set3: [Include8<A, B, C, D, E, F, G, H>] = G.samples.map(Include8<A, B, C, D, E, F, G, H>.init)
+			+ H.samples.map(Include8<A, B, C, D, E, F, G, H>.init)
+
+		return set1 + set2 + set3
+	}
+}
+
+extension Include9: Sampleable where A: Sampleable, B: Sampleable, C: Sampleable, D: Sampleable, E: Sampleable, F: Sampleable, G: Sampleable, H: Sampleable, I: Sampleable {
+	public static var sample: Include9<A, B, C, D, E, F, G, H, I> {
+		let randomChoice = Int.random(in: 0..<samples.count)
+
+		return samples[randomChoice]
+	}
+
+	public static var samples: [Include9<A, B, C, D, E, F, G, H, I>] {
+		let set1: [Include9<A, B, C, D, E, F, G, H, I>] = A.samples.map(Include9<A, B, C, D, E, F, G, H, I>.init)
+			+ B.samples.map(Include9<A, B, C, D, E, F, G, H, I>.init)
+			+ C.samples.map(Include9<A, B, C, D, E, F, G, H, I>.init)
+
+		let set2: [Include9<A, B, C, D, E, F, G, H, I>] = D.samples.map(Include9<A, B, C, D, E, F, G, H, I>.init)
+			+ E.samples.map(Include9<A, B, C, D, E, F, G, H, I>.init)
+			+ F.samples.map(Include9<A, B, C, D, E, F, G, H, I>.init)
+
+		let set3: [Include9<A, B, C, D, E, F, G, H, I>] = G.samples.map(Include9<A, B, C, D, E, F, G, H, I>.init)
+			+ H.samples.map(Include9<A, B, C, D, E, F, G, H, I>.init)
+			+ I.samples.map(Include9<A, B, C, D, E, F, G, H, I>.init)
+
+		return set1 + set2 + set3
+	}
+}

Sources/JSONAPIOpenAPI/Sampleable/JSONAPI+Sampleable.swift

@@ -0,0 +1,68 @@
+//
+//  JSONAPI+Sampleable.swift
+//  JSONAPIOpenAPI
+//
+//  Created by Mathew Polzin on 1/24/19.
+//
+
+import JSONAPI
+
+extension NoAttributes: Sampleable {
+	public static var sample: NoAttributes {
+		return .none
+	}
+}
+
+extension NoRelationships: Sampleable {
+	public static var sample: NoRelationships {
+		return .none
+	}
+}
+
+extension NoMetadata: Sampleable {
+	public static var sample: NoMetadata {
+		return .none
+	}
+}
+
+extension NoLinks: Sampleable {
+	public static var sample: NoLinks {
+		return .none
+	}
+}
+
+extension NoAPIDescription: Sampleable {
+	public static var sample: NoAPIDescription {
+		return .none
+	}
+}
+
+extension UnknownJSONAPIError: Sampleable {
+	public static var sample: UnknownJSONAPIError {
+		return .unknownError
+	}
+}
+
+extension Unidentified: Sampleable {
+	public static var sample: Unidentified {
+		return Unidentified()
+	}
+}
+
+extension Attribute: Sampleable where RawValue: Sampleable {
+	public static var sample: Attribute<RawValue> {
+		return .init(value: RawValue.sample)
+	}
+}
+
+extension SingleResourceBody: Sampleable where Entity: Sampleable {
+	public static var sample: SingleResourceBody<Entity> {
+		return .init(entity: Entity.sample)
+	}
+}
+
+extension ManyResourceBody: Sampleable where Entity: Sampleable {
+	public static var sample: ManyResourceBody<Entity> {
+		return .init(entities: Entity.samples)
+	}
+}

Sources/JSONAPIOpenAPI/Sampleable/Sampleable+OpenAPI.swift

@@ -0,0 +1,161 @@
+//
+//  Sampleable+OpenAPI.swift
+//  JSONAPIOpenAPI
+//
+//  Created by Mathew Polzin on 1/24/19.
+//
+
+import Foundation
+import AnyCodable
+
+public typealias SampleableOpenAPIType = Sampleable & GenericOpenAPINodeType
+
+extension Sampleable where Self: Encodable {
+	public static func genericOpenAPINode(using encoder: JSONEncoder) throws -> JSONNode {
+
+		// short circuit for dates
+		if let dateType = self as? Date.Type,
+			let node = try dateType.dateOpenAPINodeGuess(using: encoder) ?? primitiveGuess(using: encoder) {
+			return node
+		}
+
+		let mirror = Mirror(reflecting: Self.sample)
+		let properties: [(String, JSONNode)] = try mirror.children.compactMap { child in
+
+			// see if we can enumerate the possible values
+			let maybeAllCases: [AnyCodable]? = {
+				switch type(of: child.value) {
+				case let valType as AnyJSONCaseIterable.Type:
+					return valType.allCases(using: encoder)
+				case let valType as AnyWrappedJSONCaseIterable.Type:
+					return valType.allCases(using: encoder)
+				default:
+					return nil
+				}
+			}()
+
+			// try to snag an OpenAPI Node
+			let maybeOpenAPINode: JSONNode? = try {
+				switch type(of: child.value) {
+				case let valType as OpenAPINodeType.Type:
+					return try valType.openAPINode()
+
+				case let valType as RawOpenAPINodeType.Type:
+					return try valType.rawOpenAPINode()
+
+				case let valType as WrappedRawOpenAPIType.Type:
+					return try valType.wrappedOpenAPINode()
+
+				case let valType as DoubleWrappedRawOpenAPIType.Type:
+					return try valType.wrappedOpenAPINode()
+
+				case let valType as GenericOpenAPINodeType.Type:
+					return try valType.genericOpenAPINode(using: encoder)
+
+				case let valType as DateOpenAPINodeType.Type:
+					return valType.dateOpenAPINodeGuess(using: encoder)
+
+				default:
+					throw OpenAPITypeError.unknownNodeType(self)
+//					return nil
+				}
+				}()
+
+			// put it all together
+			let newNode: JSONNode?
+			if let allCases = maybeAllCases,
+				let openAPINode = maybeOpenAPINode {
+				newNode = try openAPINode.with(allowedValues: allCases)
+			} else {
+				newNode = maybeOpenAPINode
+			}
+
+			return zip(child.label, newNode) { ($0, $1) }
+		}
+
+		// if there are no properties, let's see if we are dealing
+		// with a primitive.
+		if properties.count == 0,
+			let primitive = try primitiveGuess(using: encoder) {
+			return primitive
+		}
+
+		// There should not be any duplication of keys since these are
+		// property names, but rather than risk runtime exception, we just
+		// fail to the newer value arbitrarily
+		let propertiesDict = Dictionary(properties) { _, value2 in value2 }
+
+		return .object(.init(format: .generic,
+							 required: true),
+					   .init(properties: propertiesDict))
+	}
+
+	private static func primitiveGuess(using encoder: JSONEncoder) throws -> JSONNode? {
+
+		let data = try encoder.encode(PrimitiveWrapper(primitive: Self.sample))
+		let wrappedValue = try JSONSerialization.jsonObject(with: data, options: [.allowFragments])
+
+		guard let wrapperDict = wrappedValue as? [String: Any],
+			wrapperDict.contains(where: { $0.key == "primitive" }) else {
+				throw OpenAPICodableError.primitiveGuessFailed
+		}
+
+		let value = (wrappedValue as! [String: Any])["primitive"]!
+
+		return try {
+			switch type(of: value) {
+			case let valType as OpenAPINodeType.Type:
+				return try valType.openAPINode()
+
+			case let valType as RawOpenAPINodeType.Type:
+				return try valType.rawOpenAPINode()
+
+			case let valType as WrappedRawOpenAPIType.Type:
+				return try valType.wrappedOpenAPINode()
+
+			case let valType as DoubleWrappedRawOpenAPIType.Type:
+				return try valType.wrappedOpenAPINode()
+
+			case let valType as GenericOpenAPINodeType.Type:
+				return try valType.genericOpenAPINode(using: encoder)
+
+			case let valType as DateOpenAPINodeType.Type:
+				return valType.dateOpenAPINodeGuess(using: encoder)
+
+			default:
+				return nil
+			}
+			}() ?? {
+				switch value {
+				case is String:
+					return .string(.init(format: .generic,
+										 required: true),
+								   .init())
+
+				case is Int:
+					return .integer(.init(format: .generic,
+										  required: true),
+									.init())
+
+				case is Double:
+					return .number(.init(format: .double,
+										 required: true),
+								   .init())
+
+				case is Bool:
+					return .boolean(.init(format: .generic,
+										  required: true))
+
+				default:
+					return nil
+				}
+			}()
+	}
+}
+
+// The following wrapper is only needed because JSONEncoder cannot yet encode
+// JSON fragments. It is a very unfortunate limitation that requires silly
+// workarounds in edge cases like this.
+private struct PrimitiveWrapper<Wrapped: Encodable>: Encodable {
+	let primitive: Wrapped
+}

Sources/JSONAPIOpenAPI/Sampleable/Sampleable.swift

@@ -0,0 +1,102 @@
+//
+//  Sampleable.swift
+//  JSONAPIOpenAPI
+//
+//  Created by Mathew Polzin on 1/15/19.
+//
+
+import Foundation
+
+/// A Sampleable type can provide a sample value.
+/// This is useful for reflection.
+public protocol Sampleable {
+	/// Get a sample value of type Self. This can be the
+	/// same value every time, or it can be an arbitrarily random
+	/// value each time.
+	static var sample: Self { get }
+
+	/// Get an example of success, if that is meaningful and
+	/// available. If not, will be nil.
+	///
+	/// The default implementation returns `nil`.
+	static var successSample: Self? { get }
+
+	/// Get an example of failure, if that is meaningful and
+	/// available. If not, will be nil.
+	///
+	/// The default implementation returns `nil`.
+	static var failureSample: Self? { get }
+
+	/// An array of samples of this Type.
+	///
+	/// The default implementation returns
+	/// an array with just the result of
+	/// `Self.sample` in it.
+	static var samples: [Self] { get }
+}
+
+public extension Sampleable {
+	// default implementation:
+	public static var successSample: Self? { return nil }
+
+	// default implementation:
+	public static var failureSample: Self? { return nil }
+
+	// default implementation:
+	public static var samples: [Self] { return [Self.sample] }
+}
+
+extension Sampleable {
+	public static func samples<S1: Sampleable>(using s1: S1.Type, with constructor: (S1) -> Self) -> [Self] {
+		return S1.samples.map(constructor)
+	}
+
+	public static func samples<S1: Sampleable, S2: Sampleable>(using s1: S1.Type, _ s2: S2.Type, with constructor: (S1, S2) -> Self) -> [Self] {
+		return zip(S1.samples, S2.samples).map(constructor)
+	}
+
+	public static func samples<S1: Sampleable, S2: Sampleable, S3: Sampleable>(using s1: S1.Type, _ s2: S2.Type, _ s3: S3.Type, with constructor: (S1, S2, S3) -> Self) -> [Self] {
+		return zip3(S1.samples, S2.samples, S3.samples).map(constructor)
+	}
+
+	public static func samples<S1: Sampleable, S2: Sampleable, S3: Sampleable, S4: Sampleable>(using s1: S1.Type, _ s2: S2.Type, _ s3: S3.Type, _ s4: S4.Type, with constructor: (S1, S2, S3, S4) -> Self) -> [Self] {
+		return zip4(S1.samples, S2.samples, S3.samples, S4.samples).map(constructor)
+	}
+
+	public static func samples<S1: Sampleable, S2: Sampleable, S3: Sampleable, S4: Sampleable, S5: Sampleable>(using s1: S1.Type, _ s2: S2.Type, _ s3: S3.Type, _ s4: S4.Type, _ s5: S5.Type, with constructor: (S1, S2, S3, S4, S5) -> Self) -> [Self] {
+		return zip5(S1.samples, S2.samples, S3.samples, S4.samples, S5.samples).map(constructor)
+	}
+
+	public static func samples<S1: Sampleable, S2: Sampleable, S3: Sampleable, S4: Sampleable, S5: Sampleable, S6: Sampleable>(using s1: S1.Type, _ s2: S2.Type, _ s3: S3.Type, _ s4: S4.Type, _ s5: S5.Type, _ s6: S6.Type, with constructor: (S1, S2, S3, S4, S5, S6) -> Self) -> [Self] {
+		// the compiler craps out at zip6. breaking it down makes the difference.
+		let firstZip = zip3(S1.samples, S2.samples, S3.samples)
+		let secondZip = zip3(S4.samples, S5.samples, S6.samples)
+		return zip(firstZip, secondZip).map { arg in (arg.0.0, arg.0.1, arg.0.2, arg.1.0, arg.1.1, arg.1.2) }.map(constructor)
+	}
+
+	public static func samples<S1: Sampleable, S2: Sampleable, S3: Sampleable, S4: Sampleable, S5: Sampleable, S6: Sampleable, S7: Sampleable>(using s1: S1.Type, _ s2: S2.Type, _ s3: S3.Type, _ s4: S4.Type, _ s5: S5.Type, _ s6: S6.Type, _ s7: S7.Type, with constructor: (S1, S2, S3, S4, S5, S6, S7) -> Self) -> [Self] {
+		// the compiler craps out at zip6. breaking it down makes the difference.
+		let firstZip = zip3(S1.samples, S2.samples, S3.samples)
+		let secondZip = zip4(S4.samples, S5.samples, S6.samples, S7.samples)
+		return zip(firstZip, secondZip).map { arg in (arg.0.0, arg.0.1, arg.0.2, arg.1.0, arg.1.1, arg.1.2, arg.1.3) }.map(constructor)
+	}
+
+	public static func samples<S1: Sampleable, S2: Sampleable, S3: Sampleable, S4: Sampleable, S5: Sampleable, S6: Sampleable, S7: Sampleable, S8: Sampleable>(using s1: S1.Type, _ s2: S2.Type, _ s3: S3.Type, _ s4: S4.Type, _ s5: S5.Type, _ s6: S6.Type, _ s7: S7.Type, _ s8: S8.Type, with constructor: (S1, S2, S3, S4, S5, S6, S7, S8) -> Self) -> [Self] {
+		// the compiler craps out at zip6. breaking it down makes the difference.
+		let firstZip = zip4(S1.samples, S2.samples, S3.samples, S4.samples)
+		let secondZip = zip4(S5.samples, S6.samples, S7.samples, S8.samples)
+		return zip(firstZip, secondZip).map { arg in (arg.0.0, arg.0.1, arg.0.2, arg.0.3, arg.1.0, arg.1.1, arg.1.2, arg.1.3) }.map(constructor)
+	}
+
+	@inlinable static func zip3<A: Sequence, B: Sequence, C: Sequence>(_ a: A, _ b: B, _ c: C) -> [(A.Element, B.Element, C.Element)] {
+		return zip(a, zip(b, c)).map { arg in (arg.0, arg.1.0, arg.1.1) }
+	}
+
+	@inlinable static func zip4<A: Sequence, B: Sequence, C: Sequence, D: Sequence>(_ a: A, _ b: B, _ c: C, _ d: D) -> [(A.Element, B.Element, C.Element, D.Element)] {
+		return zip(a, zip(b, zip(c, d))).map { arg in (arg.0, arg.1.0, arg.1.1.0, arg.1.1.1) }
+	}
+
+	@inlinable static func zip5<A: Sequence, B: Sequence, C: Sequence, D: Sequence, E: Sequence>(_ a: A, _ b: B, _ c: C, _ d: D, _ e: E) -> [(A.Element, B.Element, C.Element, D.Element, E.Element)] {
+		return zip(a, zip(b, zip(c, zip(d, e)))).map { arg in (arg.0, arg.1.0, arg.1.1.0, arg.1.1.1.0, arg.1.1.1.1) }
+	}
+}

Tests/JSONAPIOpenAPITests/JSONAPIAttributeOpenAPITests.swift

@@ -8,6 +8,7 @@
 import XCTest
 import JSONAPI
 import JSONAPIOpenAPI
+import SwiftCheck
 import AnyCodable
 
 class JSONAPIAttributeOpenAPITests: XCTestCase {
@@ -504,6 +505,361 @@ extension JSONAPIAttributeOpenAPITests {
 	}
 }
 
+// MARK: - Date
+extension JSONAPIAttributeOpenAPITests {
+	func test_DateStringAttribute() {
+		// TEST:
+		// Encoder is set to use
+		// formatter with date
+		// with no time.
+
+		let dateFormatter = DateFormatter()
+		dateFormatter.dateStyle = .medium
+		dateFormatter.timeStyle = .none
+		dateFormatter.locale = Locale(identifier: "en_US")
+
+		let encoder = JSONEncoder()
+		encoder.outputFormatting = .prettyPrinted
+		encoder.dateEncodingStrategy = .formatted(dateFormatter)
+
+		let node = Attribute<Date>.dateOpenAPINodeGuess(using: encoder)
+
+		XCTAssertNotNil(node)
+
+		XCTAssertTrue(node?.required ?? false)
+		XCTAssertEqual(node?.jsonTypeFormat, .string(.date))
+
+		guard case .string(let contextA, let stringContext)? = node else {
+			XCTFail("Expected string Node")
+			return
+		}
+
+		XCTAssertEqual(contextA, .init(format: .date,
+									   required: true,
+									   nullable: false,
+									   allowedValues: nil))
+
+		XCTAssertEqual(stringContext, .init())
+	}
+
+	func test_DateStringAttribute_Sampleable() {
+		// TEST:
+		// Encoder is set to use
+		// formatter with date
+		// with no time.
+
+		let dateFormatter = DateFormatter()
+		dateFormatter.dateStyle = .medium
+		dateFormatter.timeStyle = .none
+		dateFormatter.locale = Locale(identifier: "en_US")
+
+		let encoder = JSONEncoder()
+		encoder.outputFormatting = .prettyPrinted
+		encoder.dateEncodingStrategy = .formatted(dateFormatter)
+
+		let node = try! Attribute<Date>.genericOpenAPINode(using: encoder)
+
+		XCTAssertTrue(node.required)
+		XCTAssertEqual(node.jsonTypeFormat, .string(.date))
+
+		guard case .string(let contextA, let stringContext) = node else {
+			XCTFail("Expected string Node")
+			return
+		}
+
+		XCTAssertEqual(contextA, .init(format: .date,
+									   required: true,
+									   nullable: false,
+									   allowedValues: nil))
+
+		XCTAssertEqual(stringContext, .init())
+	}
+
+	func test_DateTimeStringAttribute() {
+		// TEST:
+		// Encoder is set to use
+		// formatter with date
+		// with time.
+
+		let dateFormatter = DateFormatter()
+		dateFormatter.dateStyle = .medium
+		dateFormatter.timeStyle = .short
+		dateFormatter.locale = Locale(identifier: "en_US")
+
+		let encoder = JSONEncoder()
+		encoder.outputFormatting = .prettyPrinted
+		encoder.dateEncodingStrategy = .formatted(dateFormatter)
+
+		let node = Attribute<Date>.dateOpenAPINodeGuess(using: encoder)
+
+		XCTAssertNotNil(node)
+
+		XCTAssertTrue(node?.required ?? false)
+		XCTAssertEqual(node?.jsonTypeFormat, .string(.dateTime))
+
+		guard case .string(let contextA, let stringContext)? = node else {
+			XCTFail("Expected string Node")
+			return
+		}
+
+		XCTAssertEqual(contextA, .init(format: .dateTime,
+									   required: true,
+									   nullable: false,
+									   allowedValues: nil))
+
+		XCTAssertEqual(stringContext, .init())
+	}
+
+	func test_DateTimeStringAttribute_Sampleable() {
+		// TEST:
+		// Encoder is set to use
+		// formatter with date
+		// with time.
+
+		let dateFormatter = DateFormatter()
+		dateFormatter.dateStyle = .medium
+		dateFormatter.timeStyle = .short
+		dateFormatter.locale = Locale(identifier: "en_US")
+
+		let encoder = JSONEncoder()
+		encoder.outputFormatting = .prettyPrinted
+		encoder.dateEncodingStrategy = .formatted(dateFormatter)
+
+		let node = try! Attribute<Date>.genericOpenAPINode(using: encoder)
+
+		XCTAssertTrue(node.required)
+		XCTAssertEqual(node.jsonTypeFormat, .string(.dateTime))
+
+		guard case .string(let contextA, let stringContext) = node else {
+			XCTFail("Expected string Node")
+			return
+		}
+
+		XCTAssertEqual(contextA, .init(format: .dateTime,
+									   required: true,
+									   nullable: false,
+									   allowedValues: nil))
+
+		XCTAssertEqual(stringContext, .init())
+	}
+
+	func test_8601DateStringAttribute() {
+		if #available(OSX 10.12, *) {
+			// TEST:
+			// Encoder is set to use
+			// iso8601 date format
+
+			let encoder = JSONEncoder()
+			encoder.outputFormatting = .prettyPrinted
+			encoder.dateEncodingStrategy = .iso8601
+
+			let node = Attribute<Date>.dateOpenAPINodeGuess(using: encoder)
+
+			XCTAssertNotNil(node)
+
+			XCTAssertTrue(node?.required ?? false)
+			XCTAssertEqual(node?.jsonTypeFormat, .string(.dateTime))
+
+			guard case .string(let contextA, let stringContext)? = node else {
+				XCTFail("Expected string Node")
+				return
+			}
+
+			XCTAssertEqual(contextA, .init(format: .dateTime,
+										   required: true,
+										   nullable: false,
+										   allowedValues: nil))
+
+			XCTAssertEqual(stringContext, .init())
+		}
+	}
+
+	func test_8601DateStringAttribute_Sampleable() {
+		if #available(OSX 10.12, *) {
+			// TEST:
+			// Encoder is set to use
+			// iso8601 date format
+
+			let encoder = JSONEncoder()
+			encoder.outputFormatting = .prettyPrinted
+			encoder.dateEncodingStrategy = .iso8601
+
+			let node = try! Attribute<Date>.genericOpenAPINode(using: encoder)
+
+			XCTAssertTrue(node.required)
+			XCTAssertEqual(node.jsonTypeFormat, .string(.dateTime))
+
+			guard case .string(let contextA, let stringContext) = node else {
+				XCTFail("Expected string Node")
+				return
+			}
+
+			XCTAssertEqual(contextA, .init(format: .dateTime,
+										   required: true,
+										   nullable: false,
+										   allowedValues: nil))
+
+			XCTAssertEqual(stringContext, .init())
+		}
+	}
+
+	func test_DateNumberAttribute() {
+		// TEST:
+		// Encoder is set to use
+		// seconds since 1970 as
+		// date format
+
+		let encoder = JSONEncoder()
+		encoder.outputFormatting = .prettyPrinted
+		encoder.dateEncodingStrategy = .secondsSince1970
+
+		let node = Attribute<Date>.dateOpenAPINodeGuess(using: encoder)
+
+		XCTAssertNotNil(node)
+
+		XCTAssertTrue(node?.required ?? false)
+		XCTAssertEqual(node?.jsonTypeFormat, .number(.double))
+
+		guard case .number(let contextA, let numberContext)? = node else {
+			XCTFail("Expected string Node")
+			return
+		}
+
+		XCTAssertEqual(contextA, .init(format: .double,
+									   required: true,
+									   nullable: false,
+									   allowedValues: nil))
+
+		XCTAssertEqual(numberContext, .init())
+	}
+
+	func test_DateNumberAttribute_Sampleable() {
+		// TEST:
+		// Encoder is set to use
+		// seconds since 1970 as
+		// date format
+
+		let encoder = JSONEncoder()
+		encoder.outputFormatting = .prettyPrinted
+		encoder.dateEncodingStrategy = .secondsSince1970
+
+		let node = try! Attribute<Date>.genericOpenAPINode(using: encoder)
+
+		XCTAssertTrue(node.required)
+		XCTAssertEqual(node.jsonTypeFormat, .number(.double))
+
+		guard case .number(let contextA, let numberContext) = node else {
+			XCTFail("Expected string Node")
+			return
+		}
+
+		XCTAssertEqual(contextA, .init(format: .double,
+									   required: true,
+									   nullable: false,
+									   allowedValues: nil))
+
+		XCTAssertEqual(numberContext, .init())
+	}
+
+	func test_DateDeferredAttribute() {
+		// TEST:
+		// Encoder is set to use
+		// Date default encoding
+
+		let encoder = JSONEncoder()
+		encoder.outputFormatting = .prettyPrinted
+		encoder.dateEncodingStrategy = .deferredToDate
+
+		let node = Attribute<Date>.dateOpenAPINodeGuess(using: encoder)
+
+		XCTAssertNil(node)
+	}
+
+	func test_DateDeferredAttribute_Sampleable() {
+		// TEST:
+		// Encoder is set to use
+		// Date default encoding
+
+		let encoder = JSONEncoder()
+		encoder.outputFormatting = .prettyPrinted
+		encoder.dateEncodingStrategy = .deferredToDate
+
+		let node = try! Attribute<Date>.genericOpenAPINode(using: encoder)
+
+		XCTAssertTrue(node.required)
+		XCTAssertEqual(node.jsonTypeFormat, .number(.double))
+
+		guard case .number(let contextA, let numberContext) = node else {
+			XCTFail("Expected string Node")
+			return
+		}
+
+		XCTAssertEqual(contextA, .init(format: .double,
+									   required: true,
+									   nullable: false,
+									   allowedValues: nil))
+
+		XCTAssertEqual(numberContext, .init())
+	}
+
+//	func test_NullableEnumAttribute() {
+//		let node = try! Attribute<EnumAttribute?>.wrappedOpenAPINode()
+//
+//		XCTAssertTrue(node.required)
+//		XCTAssertEqual(node.jsonTypeFormat, .string(.generic))
+//
+//		guard case .string(let contextA, let stringContext) = node else {
+//			XCTFail("Expected string Node")
+//			return
+//		}
+//
+//		XCTAssertEqual(contextA, .init(format: .generic,
+//									   required: true,
+//									   nullable: true,
+//									   allowedValues: nil))
+//
+//		XCTAssertEqual(stringContext, .init())
+//	}
+//
+//	func test_OptionalEnumAttribute() {
+//		let node = try! Attribute<EnumAttribute>?.wrappedOpenAPINode()
+//
+//		XCTAssertFalse(node.required)
+//		XCTAssertEqual(node.jsonTypeFormat, .string(.generic))
+//
+//		guard case .string(let contextA, let stringContext) = node else {
+//			XCTFail("Expected string Node")
+//			return
+//		}
+//
+//		XCTAssertEqual(contextA, .init(format: .generic,
+//									   required: false,
+//									   nullable: false,
+//									   allowedValues: nil))
+//
+//		XCTAssertEqual(stringContext, .init())
+//	}
+//
+//	func test_OptionalNullableEnumAttribute() {
+//		let node = try! Attribute<EnumAttribute?>?.wrappedOpenAPINode()
+//
+//		XCTAssertFalse(node.required)
+//		XCTAssertEqual(node.jsonTypeFormat, .string(.generic))
+//
+//		guard case .string(let contextA, let stringContext) = node else {
+//			XCTFail("Expected string Node")
+//			return
+//		}
+//
+//		XCTAssertEqual(contextA, .init(format: .generic,
+//									   required: false,
+//									   nullable: true,
+//									   allowedValues: nil))
+//
+//		XCTAssertEqual(stringContext, .init())
+//	}
+}
+
 // MARK: - Test Types
 extension JSONAPIAttributeOpenAPITests {
 	enum EnumAttribute: String, Codable, CaseIterable {
@@ -511,3 +867,9 @@ extension JSONAPIAttributeOpenAPITests {
 		case two
 	}
 }
+
+extension Date: SampleableOpenAPIType {
+	public static var sample: Date {
+		return TimeInterval.arbitrary.map { Date(timeIntervalSince1970: $0) }.generate
+	}
+}

Tests/JSONAPIOpenAPITests/JSONAPIDocumentOpenAPITests.swift

@@ -6,15 +6,23 @@
 //
 
 import XCTest
+import SwiftCheck
 import JSONAPI
 import JSONAPIOpenAPI
 
 class JSONAPIDocumentOpenAPITests: XCTestCase {
 	func test_SingleResourceDocument() {
-		let node = try! SingleEntityDocument.openAPINode()
+
+		let dateFormatter = DateFormatter()
+		dateFormatter.dateStyle = .medium
+		dateFormatter.timeStyle = .none
+		dateFormatter.locale = Locale(identifier: "en_US")
 
 		let encoder = JSONEncoder()
 		encoder.outputFormatting = .prettyPrinted
+		encoder.dateEncodingStrategy = .formatted(dateFormatter)
+
+		let node = try! SingleEntityDocument.openAPINodeWithExample(using: encoder)
 
 		print(String(data: try! encoder.encode(node), encoding: .utf8)!)
 	}
@@ -27,9 +35,11 @@ extension JSONAPIDocumentOpenAPITests {
 
 		struct Attributes: JSONAPI.Attributes, Sampleable {
 			let name: Attribute<String>
+			let date: Attribute<Date>
 
 			static var sample: Attributes {
-				return .init(name: "hello world")
+				return .init(name: "hello world",
+							 date: .init(value: Date()))
 			}
 		}
 
@@ -40,3 +50,29 @@ extension JSONAPIDocumentOpenAPITests {
 
 	typealias SingleEntityDocument = Document<SingleResourceBody<TestEntity>, NoMetadata, NoLinks, NoIncludes, NoAPIDescription, UnknownJSONAPIError>
 }
+
+extension Id: Sampleable where RawType == String {
+	public static var sample: Id<RawType, IdentifiableType> {
+		return .init(rawValue: String.arbitrary.generate)
+	}
+}
+
+extension JSONAPI.Entity: Sampleable where Description.Attributes: Sampleable, Description.Relationships: Sampleable, MetaType: Sampleable, LinksType: Sampleable, EntityRawIdType == String {
+	public static var sample: JSONAPI.Entity<Description, MetaType, LinksType, EntityRawIdType> {
+		return JSONAPI.Entity(id: .sample,
+							  attributes: .sample,
+							  relationships: .sample,
+							  meta: .sample,
+							  links: .sample)
+	}
+}
+
+extension Document: Sampleable where PrimaryResourceBody: Sampleable, MetaType: Sampleable, LinksType: Sampleable, IncludeType: Sampleable, APIDescription: Sampleable, Error: Sampleable {
+	public static var sample: Document<PrimaryResourceBody, MetaType, LinksType, IncludeType, APIDescription, Error> {
+		return Document(apiDescription: .sample,
+						body: .sample,
+						includes: .sample,
+						meta: .sample,
+						links: .sample)
+	}
+}

Tests/JSONAPIOpenAPITests/JSONAPIEntityOpenAPITests.swift

@@ -12,7 +12,7 @@ import AnyCodable
 
 class JSONAPIEntityOpenAPITests: XCTestCase {
 	func test_EmptyEntity() {
-		let node = try! TestType1.openAPINode()
+		let node = try! TestType1.openAPINode(using: JSONEncoder())
 
 		XCTAssertTrue(node.required)
 		XCTAssertEqual(node.jsonTypeFormat, .object(.generic))
@@ -40,7 +40,16 @@ class JSONAPIEntityOpenAPITests: XCTestCase {
 	}
 
 	func test_AttributesEntity() {
-		let node = try! TestType2.openAPINode()
+
+		let dateFormatter = DateFormatter()
+		dateFormatter.dateStyle = .medium
+		dateFormatter.timeStyle = .short
+		dateFormatter.locale = Locale(identifier: "en_US")
+
+		let encoder = JSONEncoder()
+		encoder.dateEncodingStrategy = .formatted(dateFormatter)
+
+		let node = try! TestType2.openAPINode(using: encoder)
 
 		XCTAssertTrue(node.required)
 		XCTAssertEqual(node.jsonTypeFormat, .object(.generic))
@@ -83,9 +92,9 @@ class JSONAPIEntityOpenAPITests: XCTestCase {
 									   nullable: false,
 									   allowedValues: nil))
 
-		XCTAssertEqual(attributesContext.minProperties, 3)
-		XCTAssertEqual(Set(attributesContext.requiredProperties), Set(["stringProperty", "enumProperty", "nullableProperty"]))
-		XCTAssertEqual(Set(attributesContext.properties.keys), Set(["stringProperty", "enumProperty", "optionalProperty", "nullableProperty", "nullableOptionalProperty"]))
+		XCTAssertEqual(attributesContext.minProperties, 4)
+		XCTAssertEqual(Set(attributesContext.requiredProperties), Set(["stringProperty", "enumProperty", "dateProperty", "nullableProperty"]))
+		XCTAssertEqual(Set(attributesContext.properties.keys), Set(["stringProperty", "enumProperty", "dateProperty", "optionalProperty", "nullableProperty", "nullableOptionalProperty"]))
 
 		XCTAssertEqual(attributesContext.properties["stringProperty"],
 					   .string(.init(format: .generic,
@@ -99,6 +108,13 @@ class JSONAPIEntityOpenAPITests: XCTestCase {
 									 allowedValues: ["one", "two"].map(AnyCodable.init)),
 							   .init()))
 
+		XCTAssertEqual(attributesContext.properties["dateProperty"],
+					   .string(.init(format: .dateTime,
+									 required: true,
+									 nullable: false,
+									 allowedValues: nil),
+							   .init()))
+
 		XCTAssertEqual(attributesContext.properties["optionalProperty"],
 					   .string(.init(format: .generic,
 									 required: false,
@@ -122,7 +138,7 @@ class JSONAPIEntityOpenAPITests: XCTestCase {
 	}
 
 	func test_RelationshipsEntity() {
-		let node = try! TestType3.openAPINode()
+		let node = try! TestType3.openAPINode(using: JSONEncoder())
 
 		XCTAssertTrue(node.required)
 		XCTAssertEqual(node.jsonTypeFormat, .object(.generic))
@@ -268,6 +284,7 @@ extension JSONAPIEntityOpenAPITests {
 		public struct Attributes: JSONAPI.Attributes, Sampleable {
 			let stringProperty: Attribute<String>
 			let enumProperty: Attribute<EnumType>
+			let dateProperty: Attribute<Date>
 			let optionalProperty: Attribute<String>?
 			let nullableProperty: Attribute<String?>
 			let nullableOptionalProperty: Attribute<String?>?
@@ -278,6 +295,7 @@ extension JSONAPIEntityOpenAPITests {
 			public static var sample: Attributes {
 				return Attributes(stringProperty: .init(value: "hello"),
 								  enumProperty: .init(value: .one),
+								  dateProperty: .init(value: Date()),
 								  optionalProperty: nil,
 								  nullableProperty: .init(value: nil),
 								  nullableOptionalProperty: nil)