Add support for 'const' via OpenAPI 3.0 workaround suggested by others: Use 'enum' with one value. Add Sampleable support for requesting samples representing 'success' and 'failure' if available.

Sources/JSONAPIOpenAPI/JSONAPITypes+OpenAPI.swift

@@ -72,13 +72,14 @@ extension TransformedAttribute: OpenAPINodeType where RawValue: OpenAPINodeType
 }
 
 extension RelationshipType {
-	static func relationshipNode(nullable: Bool) -> JSONNode {
+	static func relationshipNode(nullable: Bool, jsonType: String) -> JSONNode {
 		let propertiesDict: [String: JSONNode] = [
 			"id": .string(.init(format: .generic,
 								required: true),
 						  .init()),
 			"type": .string(.init(format: .generic,
-								  required: true),
+								  required: true,
+								  allowedValues: [.init(jsonType)]),
 							.init())
 		]
 
@@ -97,7 +98,7 @@ extension ToOneRelationship: OpenAPINodeType {
 		return .object(.init(format: .generic,
 							 required: true),
 					   .init(properties: [
-						"data": ToOneRelationship.relationshipNode(nullable: nullable)
+						"data": ToOneRelationship.relationshipNode(nullable: nullable, jsonType: Identifiable.jsonType)
 						]))
 	}
 }
@@ -111,14 +112,16 @@ extension ToManyRelationship: OpenAPINodeType {
 					   .init(properties: [
 						"data": .array(.init(format: .generic,
 											 required: true),
-									   .init(items: ToManyRelationship.relationshipNode(nullable: false)))
+									   .init(items: ToManyRelationship.relationshipNode(nullable: false, jsonType: Relatable.jsonType)))
 						]))
 	}
 }
 
 extension Entity: OpenAPINodeType where Description.Attributes: Sampleable, Description.Relationships: Sampleable {
 	public static func openAPINode() throws -> JSONNode {
-		// TODO: const for json `type`
+		// NOTE: const for json `type` not supported by OpenAPI 3.0
+		//		Will use "enum" with one possible value for now.
+
 		// TODO: metadata, links
 
 		let idNode = JSONNode.string(.init(format: .generic,
@@ -127,7 +130,8 @@ extension Entity: OpenAPINodeType where Description.Attributes: Sampleable, Desc
 		let idProperty = ("id", idNode)
 
 		let typeNode = JSONNode.string(.init(format: .generic,
-											 required: true),
+											 required: true,
+											 allowedValues: [.init(Entity.jsonType)]),
 									   .init())
 		let typeProperty = ("type", typeNode)
 

Sources/JSONAPIOpenAPI/OpenAPITypes+Codable.swift

@@ -13,6 +13,7 @@ extension JSONNode.Context: Encodable {
 		case allowedValues = "enum"
 		case nullable
 		case example
+//		case constantValue = "const"
 	}
 
 	public func encode(to encoder: Encoder) throws {
@@ -28,6 +29,10 @@ extension JSONNode.Context: Encodable {
 			try container.encode(allowedValues, forKey: .allowedValues)
 		}
 
+//		if constantValue != nil {
+//			try container.encode(constantValue, forKey: .constantValue)
+//		}
+
 		try container.encode(nullable, forKey: .nullable)
 
 		if example != nil {

Sources/JSONAPIOpenAPI/OpenAPITypes.swift

@@ -18,7 +18,7 @@ public protocol OpenAPINodeType {
 
 extension OpenAPINodeType where Self: Sampleable, Self: Encodable {
 	public static func openAPINodeWithExample() throws -> JSONNode {
-		return try openAPINode().with(example: Self.sample)
+		return try openAPINode().with(example: Self.successSample ?? Self.sample)
 	}
 }
 
@@ -255,6 +255,10 @@ public enum JSONNode: Equatable {
 		public let required: Bool
 		public let nullable: Bool
 
+		// NOTE: "const" is supported by the newest JSON Schema spec but not
+		// yet by OpenAPI. Instead, will use "enum" with one possible value for now.
+//		public let constantValue: Format.SwiftType?
+
 		/// The OpenAPI spec calls this "enum"
 		/// If not specified, it is assumed that any
 		/// value of the given format is allowed.
@@ -276,11 +280,13 @@ public enum JSONNode: Equatable {
 		public init(format: Format,
 					required: Bool,
 					nullable: Bool = false,
+//					constantValue: Format.SwiftType? = nil,
 					allowedValues: [AnyCodable]? = nil,
 					example: AnyCodable? = nil) {
 			self.format = format
 			self.required = required
 			self.nullable = nullable
+//			self.constantValue = constantValue
 			self.allowedValues = allowedValues
 			self.example = example
 				.flatMap { try? JSONEncoder().encode($0)}
@@ -292,6 +298,7 @@ public enum JSONNode: Equatable {
 			return .init(format: format,
 						 required: false,
 						 nullable: nullable,
+//						 constantValue: constantValue,
 						 allowedValues: allowedValues)
 		}
 
@@ -300,6 +307,7 @@ public enum JSONNode: Equatable {
 			return .init(format: format,
 						 required: true,
 						 nullable: nullable,
+//						 constantValue: constantValue,
 						 allowedValues: allowedValues)
 		}
 
@@ -308,6 +316,7 @@ public enum JSONNode: Equatable {
 			return .init(format: format,
 						 required: required,
 						 nullable: true,
+//						 constantValue: constantValue,
 						 allowedValues: allowedValues)
 		}
 
@@ -316,6 +325,7 @@ public enum JSONNode: Equatable {
 			return .init(format: format,
 						 required: required,
 						 nullable: nullable,
+//						 constantValue: constantValue,
 						 allowedValues: allowedValues)
 		}
 
@@ -324,6 +334,7 @@ public enum JSONNode: Equatable {
 			return .init(format: format,
 						 required: required,
 						 nullable: nullable,
+//						 constantValue: constantValue,
 						 allowedValues: allowedValues,
 						 example: example)
 		}

Sources/JSONAPIOpenAPI/Sampleable.swift

@@ -15,6 +15,20 @@ public protocol Sampleable {
 	/// 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 {