Add parsing invariant structure even though I do not have a solid enough use-case to implement an invariant fully just yet.

README.md

@@ -67,7 +67,7 @@ Note that Playground support for importing non-system Frameworks is still a bit
 ### JSONAPITestLib
 #### Entity Validator
 - [x] Disallow optional array in `Attribute` (should be empty array, not `null`).
-- [x] Only allow `TransformedAttribute` and its derivatives within `Attributes` struct.
+- [x] Only allow `TransformedAttribute` and its derivatives as stored properties within `Attributes` struct. Computed properties can still be any type because they do not get encoded or decoded.
 - [x] Only allow `ToManyRelationship` and `ToOneRelationship` within `Relationships` struct.
 
 ### Potential Improvements
@@ -273,6 +273,23 @@ public var fullName: Attribute<String> {
 }
 ```
 
+### Copying `Entities`
+`Entity` is a value type, so copying is its default behavior. There are two common mutations you might want to make when copying an `Entity`:
+1. Assigning a new `Identifier` to the copy of an identified `Entity`.
+2. Assigning a new `Identifier` to the copy of an unidentified `Entity`.
+
+The above can be accomplished with code like the following:
+
+```
+// use case 1
+let person1 = person.withNewIdentifier()
+
+// use case 2
+let newlyIdentifiedPerson1 = unidentifiedPerson.identified(byType: String.self)
+
+let newlyIdentifiedPerson2 = unidentifiedPerson.identified(by: "2232")
+```
+
 ### `JSONAPI.Document`
 
 The entirety of a JSON API request or response is encoded or decoded from- or to a `Document`. As an example, a JSON API response containing one `Person` and no included entities could be decoded as follows:

Sources/JSONAPI/Document/Document.swift

@@ -66,8 +66,13 @@ public struct Document<PrimaryResourceBody: JSONAPI.ResourceBody, MetaType: JSON
 			guard case let .errors(errors, meta: _, links: _) = self else { return nil }
 			return errors
 		}
+
+		public var data: Data? {
+			guard case let .data(data) = self else { return nil }
+			return data
+		}
 		
-		public var primaryData: PrimaryResourceBody? {
+		public var primaryResource: PrimaryResourceBody? {
 			guard case let .data(data) = self else { return nil }
 			return data.primary
 		}

Sources/JSONAPI/Invariants/ParsingInvariant.swift

@@ -0,0 +1,76 @@
+//
+//  ParsingInvariant.swift
+//  JSONAPI
+//
+//  Created by Mathew Polzin on 12/24/18.
+//
+
+/// An Error produced when an invariant fails.
+public enum InvariantError: Swift.Error {
+	case failure(description: String)
+}
+
+/// Set a reaction to a particular type of invariant failure.
+/// `Warning` and `Quiet` will take a default strategy for handling
+/// the invariant and parsing will not fail. `Error` will cause parsing
+/// to fail due to the given invariant failing.
+public protocol IReaction {
+	/// Perform the given Invariant strategy.
+	static func trigger(invariant: InvariantType.Type) throws
+}
+
+public enum Invariant {
+	/// Used to indicate an invariant failure shoud be considered an error.
+	/// Parsing will fail if an Error invariant fails.
+	public enum Error: IReaction {
+		public static func trigger(invariant: InvariantType.Type) throws {
+			throw InvariantError.failure(description: String(describing: invariant))
+		}
+	}
+
+	/// Used to indicate an invariant failure should be considered a warning.
+	/// The invariant description will be printed to the console but parsing
+	/// will not fail. A default strategy for addressing the invariant will
+	/// be taken. See the given invariant's documentation for details.
+	public enum Warning: IReaction {
+		public static func trigger(invariant: InvariantType.Type) throws {
+			print("**WARN** \(String(describing: invariant))")
+		}
+	}
+
+	/// Used to indicate an invariant failures should be considered inconsequential.
+	/// Parsing will continue and a default strategy for addressing the invariant
+	/// will be taken. See the given invariant's documentation for details.
+	public enum Quiet: IReaction {
+		public static func trigger(invariant: InvariantType.Type) throws {}
+	}
+
+	/// A strategy pairs an invariant type with the desired reaction.
+	public enum Strategy<IType: InvariantType, IReaction: JSONAPI.IReaction>: IStrategy {}
+}
+
+public protocol InvariantType {}
+
+public protocol IStrategy {
+	associatedtype IType: InvariantType
+	associatedtype IReaction: JSONAPI.IReaction
+}
+
+// TODO: Does this invariant make sense? I can't actually know whether arbitrary
+// Id types are "empty" so I think I started down this path without having fully
+// thought through it. Perhaps there are still other obvious invariants to add
+// though.
+public protocol RelationshipNonEmptyIdInvariant: IStrategy where IType == Invariant.Relationships.NonEmptyId {}
+
+extension Invariant {
+	public enum Relationships {
+
+		/// The Empty Id Invariant holds as long as a relationships's Id
+		/// is not "empty"
+		public enum NonEmptyId: InvariantType {}
+
+		public enum Strategies<NonEmptyId: RelationshipNonEmptyIdInvariant> {}
+	}
+}
+
+// Would be used like `ToOneRelationship<OtherEntity, Invariant.Relationships.Strategies<Invariant.Strategy<Invariant.Relationships.NonEmptyId, Invariant.Error>>>`

Sources/JSONAPI/Resource/Attribute.swift

@@ -11,7 +11,7 @@ public protocol AttributeType: Codable {
 // MARK: TransformedAttribute
 /// A TransformedAttribute takes a Codable type and attempts to turn it into another type.
 public struct TransformedAttribute<RawValue: Codable, Transformer: JSONAPI.Transformer>: AttributeType where Transformer.From == RawValue {
-	private let rawValue: RawValue
+	let rawValue: RawValue
 	
 	public let value: Transformer.To
 	

Sources/JSONAPI/Resource/Entity.swift

@@ -32,21 +32,25 @@ public protocol JSONTyped {
 	static var type: String { get }
 }
 
+/// An `EntityProxyDescription` is an `EntityDescription`
+/// without Codable conformance.
+public protocol EntityProxyDescription: JSONTyped {
+	associatedtype Attributes: Equatable
+	associatedtype Relationships: Equatable
+}
+
 /// An `EntityDescription` describes a JSON API
 /// Resource Object. The Resource Object
 /// itself is encoded and decoded as an
 /// `Entity`, which gets specialized on an
 /// `EntityDescription`.
-public protocol EntityDescription: JSONTyped {
-	associatedtype Attributes: JSONAPI.Attributes
-	associatedtype Relationships: JSONAPI.Relationships
-}
+public protocol EntityDescription: EntityProxyDescription where Attributes: JSONAPI.Attributes, Relationships: JSONAPI.Relationships {}
 
 /// EntityProxy is a protocol that can be used to create
 /// types that _act_ like Entities but cannot be encoded
 /// or decoded as Entities.
 public protocol EntityProxy: Equatable, JSONTyped {
-	associatedtype Description: EntityDescription
+	associatedtype Description: EntityProxyDescription
 	associatedtype EntityRawIdType: JSONAPI.MaybeRawId
 
 	typealias Id = JSONAPI.Id<EntityRawIdType, Self>
@@ -75,7 +79,9 @@ extension EntityProxy {
 /// EntityType is the protocol that Entity conforms to. This
 /// protocol lets other types accept any Entity as a generic
 /// specialization.
-public protocol EntityType: EntityProxy, PrimaryResource {
+public protocol EntityType: EntityProxy, PrimaryResource where Description: EntityDescription {
+	associatedtype Meta: JSONAPI.Meta
+	associatedtype Links: JSONAPI.Links
 }
 
 public protocol IdentifiableEntityType: EntityType, Relatable where EntityRawIdType: JSONAPI.RawIdType {}
@@ -85,6 +91,10 @@ public protocol IdentifiableEntityType: EntityType, Relatable where EntityRawIdT
 /// "Resource Object."
 /// See https://jsonapi.org/format/#document-resource-objects
 public struct Entity<Description: JSONAPI.EntityDescription, MetaType: JSONAPI.Meta, LinksType: JSONAPI.Links, EntityRawIdType: JSONAPI.MaybeRawId>: EntityType {
+
+	public typealias Meta = MetaType
+	public typealias Links = LinksType
+
 	/// The `Entity`'s Id. This can be of type `Unidentified` if
 	/// the entity is being created clientside and the
 	/// server is being asked to create a unique Id. Otherwise,
@@ -377,10 +387,15 @@ extension Entity where MetaType == NoMetadata, LinksType == NoLinks, EntityRawId
 public extension Entity where EntityRawIdType: JSONAPI.RawIdType {
 
 	/// An Entity.Pointer is a `ToOneRelationship` with no metadata or links.
-	/// This is just a convenient way to reference an Entity given that
+	/// This is just a convenient way to reference an Entity so that
 	/// other Entities' Relationships can be built up from it.
 	public typealias Pointer = ToOneRelationship<Entity, NoMetadata, NoLinks>
 
+	/// Entity.Pointers is a `ToManyRelationship` with no metadata or links.
+	/// This is just a convenient way to reference a bunch of Entities so
+	/// that other Entities' Relationships can be built up from them.
+	public typealias Pointers = ToManyRelationship<Entity, NoMetadata, NoLinks>
+
 	/// Get a pointer to this entity that can be used as a
 	/// relationship to another entity.
 	public var pointer: Pointer {
@@ -392,6 +407,27 @@ public extension Entity where EntityRawIdType: JSONAPI.RawIdType {
 	}
 }
 
+// MARK: Identifying Unidentified Entities
+public extension Entity where EntityRawIdType == Unidentified {
+	/// Create a new Entity from this one with a newly created
+	/// unique Id of the given type.
+	public func identified<RawIdType: CreatableRawIdType>(byType: RawIdType.Type) -> Entity<Description, MetaType, LinksType, RawIdType> {
+		return .init(attributes: attributes, relationships: relationships, meta: meta, links: links)
+	}
+
+	/// Create a new Entity from this one with the given Id.
+	public func identified<RawIdType: JSONAPI.RawIdType>(by id: RawIdType) -> Entity<Description, MetaType, LinksType, RawIdType> {
+		return .init(id: Entity<Description, MetaType, LinksType, RawIdType>.Identifier(rawValue: id), attributes: attributes, relationships: relationships, meta: meta, links: links)
+	}
+}
+
+public extension Entity where EntityRawIdType: CreatableRawIdType {
+	/// Create a copy of this Entity with a new unique Id.
+	public func withNewIdentifier() -> Entity {
+		return Entity(attributes: attributes, relationships: relationships, meta: meta, links: links)
+	}
+}
+
 // MARK: Attribute Access
 public extension EntityProxy {
 	/// Access the attribute at the given keypath. This just

Tests/JSONAPITests/Attribute/AttributeTests.swift

@@ -30,6 +30,18 @@ class AttributeTests: XCTestCase {
 		XCTAssertNoThrow(try TransformedAttribute<String, TestTransformer>(transformedValue: 10))
 	}
 
+	func test_EncodedPrimitives() {
+		testEncodedPrimitive(attribute: Attribute<Int>(value: 10))
+		testEncodedPrimitive(attribute: Attribute<Bool>(value: false))
+		testEncodedPrimitive(attribute: Attribute<Double>(value: 10.2))
+
+		testEncodedPrimitive(attribute: try! TransformedAttribute<Int, IntToString>(rawValue: 10))
+		testEncodedPrimitive(attribute: try! TransformedAttribute<Int, IntToInt>(rawValue: 10))
+		testEncodedPrimitive(attribute: try! TransformedAttribute<Int, IntToDouble>(rawValue: 10))
+		testEncodedPrimitive(attribute: try! TransformedAttribute<String, TestTransformer>(rawValue: "10"))
+		testEncodedPrimitive(attribute: try! TransformedAttribute<String?, OptionalToString<String>>(rawValue: "10"))
+	}
+
 	func test_NullableIsNullIfNil() {
 		struct Wrapper: Codable {
 			let dummy: Attribute<String?>
@@ -68,4 +80,28 @@ extension AttributeTests {
 			return String(value)
 		}
 	}
+
+	enum IntToString: Transformer {
+		public static func transform(_ from: Int) -> String {
+			return String(from)
+		}
+	}
+
+	enum IntToInt: Transformer {
+		public static func transform(_ from: Int) -> Int {
+			return from + 100
+		}
+	}
+
+	enum IntToDouble: Transformer {
+		public static func transform(_ from: Int) -> Double {
+			return Double(from)
+		}
+	}
+
+	enum OptionalToString<T>: Transformer {
+		public static func transform(_ from: T?) -> String {
+			return String(describing: from)
+		}
+	}
 }

Tests/JSONAPITests/Document/DocumentTests.swift

@@ -16,9 +16,9 @@ class DocumentTests: XCTestCase {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
+		XCTAssertNotNil(document.body.primaryResource)
 		XCTAssertEqual(document.body.meta, NoMetadata())
-		XCTAssertNil(document.body.primaryData?.value)
+		XCTAssertNil(document.body.primaryResource?.value)
 		XCTAssertEqual(document.body.includes?.count, 0)
 		XCTAssertEqual(document.body.links, NoLinks())
 		XCTAssertEqual(document.apiDescription, .none)
@@ -35,9 +35,9 @@ class DocumentTests: XCTestCase {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
+		XCTAssertNotNil(document.body.primaryResource)
 		XCTAssertEqual(document.body.meta, NoMetadata())
-		XCTAssertNil(document.body.primaryData?.value)
+		XCTAssertNil(document.body.primaryResource?.value)
 		XCTAssertEqual(document.body.includes?.count, 0)
 		XCTAssertEqual(document.body.links, NoLinks())
 		XCTAssertEqual(document.apiDescription.version, "1.0")
@@ -73,7 +73,7 @@ extension DocumentTests {
 
 		XCTAssertTrue(document.body.isError)
 		XCTAssertEqual(document.body.meta, NoMetadata())
-		XCTAssertNil(document.body.primaryData)
+		XCTAssertNil(document.body.primaryResource)
 		XCTAssertNil(document.body.includes)
 
 		guard case let .errors(errors) = document.body else {
@@ -98,7 +98,7 @@ extension DocumentTests {
 
 		XCTAssertTrue(document.body.isError)
 		XCTAssertEqual(document.body.meta, NoMetadata())
-		XCTAssertNil(document.body.primaryData)
+		XCTAssertNil(document.body.primaryResource)
 		XCTAssertNil(document.body.includes)
 		XCTAssertEqual(document.apiDescription.version, "1.0")
 
@@ -123,7 +123,7 @@ extension DocumentTests {
 
 		XCTAssertTrue(document.body.isError)
 		XCTAssertNil(document.body.meta)
-		XCTAssertNil(document.body.primaryData)
+		XCTAssertNil(document.body.primaryResource)
 		XCTAssertNil(document.body.includes)
 
 		guard case let .errors(errors) = document.body else {
@@ -146,7 +146,7 @@ extension DocumentTests {
 
 		XCTAssertTrue(document.body.isError)
 		XCTAssertNil(document.body.meta)
-		XCTAssertNil(document.body.primaryData)
+		XCTAssertNil(document.body.primaryResource)
 		XCTAssertNil(document.body.includes)
 		XCTAssertEqual(document.apiDescription.version, "1.0")
 
@@ -171,7 +171,7 @@ extension DocumentTests {
 
 		XCTAssertTrue(document.body.isError)
 		XCTAssertEqual(document.body.meta, NoMetadata())
-		XCTAssertNil(document.body.primaryData)
+		XCTAssertNil(document.body.primaryResource)
 		XCTAssertNil(document.body.includes)
 
 		guard case let .errors(errors) = document.body else {
@@ -196,7 +196,7 @@ extension DocumentTests {
 
 		XCTAssertTrue(document.body.isError)
 		XCTAssertEqual(document.body.meta, NoMetadata())
-		XCTAssertNil(document.body.primaryData)
+		XCTAssertNil(document.body.primaryResource)
 		XCTAssertNil(document.body.includes)
 		XCTAssertEqual(document.apiDescription.version, "1.0")
 
@@ -222,7 +222,7 @@ extension DocumentTests {
 
 		XCTAssertTrue(document.body.isError)
 		XCTAssertEqual(document.body.meta, TestPageMetadata(total: 70, limit: 40, offset: 10))
-		XCTAssertNil(document.body.primaryData)
+		XCTAssertNil(document.body.primaryResource)
 		XCTAssertNil(document.body.includes)
 
 		guard case let .errors(errors) = document.body else {
@@ -246,7 +246,7 @@ extension DocumentTests {
 
 		XCTAssertTrue(document.body.isError)
 		XCTAssertEqual(document.body.meta, TestPageMetadata(total: 70, limit: 40, offset: 10))
-		XCTAssertNil(document.body.primaryData)
+		XCTAssertNil(document.body.primaryResource)
 		XCTAssertNil(document.body.includes)
 		XCTAssertEqual(document.apiDescription.version, "1.0")
 
@@ -271,7 +271,7 @@ extension DocumentTests {
 
 		XCTAssertTrue(document.body.isError)
 		XCTAssertEqual(document.body.meta, TestPageMetadata(total: 70, limit: 40, offset: 10))
-		XCTAssertNil(document.body.primaryData)
+		XCTAssertNil(document.body.primaryResource)
 		XCTAssertNil(document.body.includes)
 
 		guard case let .errors(errors) = document.body else {
@@ -299,7 +299,7 @@ extension DocumentTests {
 
 		XCTAssertTrue(document.body.isError)
 		XCTAssertEqual(document.body.meta, TestPageMetadata(total: 70, limit: 40, offset: 10))
-		XCTAssertNil(document.body.primaryData)
+		XCTAssertNil(document.body.primaryResource)
 		XCTAssertNil(document.body.includes)
 		XCTAssertEqual(document.apiDescription.version, "1.0")
 
@@ -327,7 +327,7 @@ extension DocumentTests {
 							   data: error_document_with_links)
 
 		XCTAssertTrue(document.body.isError)
-		XCTAssertNil(document.body.primaryData)
+		XCTAssertNil(document.body.primaryResource)
 		XCTAssertNil(document.body.includes)
 
 		guard case let .errors(errors) = document.body else {
@@ -353,7 +353,7 @@ extension DocumentTests {
 							   data: error_document_with_links_with_api_description)
 
 		XCTAssertTrue(document.body.isError)
-		XCTAssertNil(document.body.primaryData)
+		XCTAssertNil(document.body.primaryResource)
 		XCTAssertNil(document.body.includes)
 		XCTAssertEqual(document.apiDescription.version, "1.0")
 
@@ -380,7 +380,7 @@ extension DocumentTests {
 							   data: error_document_no_metadata)
 
 		XCTAssertTrue(document.body.isError)
-		XCTAssertNil(document.body.primaryData)
+		XCTAssertNil(document.body.primaryResource)
 		XCTAssertNil(document.body.includes)
 
 		guard case let .errors(errors) = document.body else {
@@ -403,7 +403,7 @@ extension DocumentTests {
 							   data: error_document_no_metadata_with_api_description)
 
 		XCTAssertTrue(document.body.isError)
-		XCTAssertNil(document.body.primaryData)
+		XCTAssertNil(document.body.primaryResource)
 		XCTAssertNil(document.body.includes)
 		XCTAssertEqual(document.apiDescription.version, "1.0")
 
@@ -523,8 +523,8 @@ extension DocumentTests {
 		
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.value.id.rawValue, "1")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.value.id.rawValue, "1")
 		XCTAssertEqual(document.body.includes?.count, 0)
 		XCTAssertEqual(document.body.meta, NoMetadata())
 	}
@@ -540,8 +540,8 @@ extension DocumentTests {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.value.id.rawValue, "1")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.value.id.rawValue, "1")
 		XCTAssertEqual(document.body.includes?.count, 0)
 		XCTAssertEqual(document.body.meta, NoMetadata())
 		XCTAssertEqual(document.apiDescription.version, "1.0")
@@ -558,8 +558,8 @@ extension DocumentTests {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.value?.id.rawValue, "1")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.value?.id.rawValue, "1")
 		XCTAssertEqual(document.body.includes?.count, 0)
 		XCTAssertEqual(document.body.meta, NoMetadata())
 	}
@@ -575,8 +575,8 @@ extension DocumentTests {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.value?.id.rawValue, "1")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.value?.id.rawValue, "1")
 		XCTAssertEqual(document.body.includes?.count, 0)
 		XCTAssertEqual(document.body.meta, NoMetadata())
 		XCTAssertEqual(document.apiDescription.version, "1.0")
@@ -593,8 +593,8 @@ extension DocumentTests {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.value.id.rawValue, "1")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.value.id.rawValue, "1")
 		XCTAssertEqual(document.body.includes?.count, 0)
 		XCTAssertEqual(document.body.meta, TestPageMetadata(total: 70, limit: 40, offset: 10))
 	}
@@ -610,8 +610,8 @@ extension DocumentTests {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.value.id.rawValue, "1")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.value.id.rawValue, "1")
 		XCTAssertEqual(document.body.includes?.count, 0)
 		XCTAssertEqual(document.body.meta, TestPageMetadata(total: 70, limit: 40, offset: 10))
 		XCTAssertEqual(document.apiDescription.version, "1.0")
@@ -628,8 +628,8 @@ extension DocumentTests {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.value.id.rawValue, "1")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.value.id.rawValue, "1")
 		XCTAssertEqual(document.body.includes?.count, 0)
 		XCTAssertEqual(document.body.meta, NoMetadata())
 		XCTAssertEqual(document.body.links?.link.url, "https://website.com")
@@ -650,8 +650,8 @@ extension DocumentTests {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.value.id.rawValue, "1")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.value.id.rawValue, "1")
 		XCTAssertEqual(document.body.includes?.count, 0)
 		XCTAssertEqual(document.body.meta, NoMetadata())
 		XCTAssertEqual(document.body.links?.link.url, "https://website.com")
@@ -673,8 +673,8 @@ extension DocumentTests {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.value.id.rawValue, "1")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.value.id.rawValue, "1")
 		XCTAssertEqual(document.body.includes?.count, 0)
 		XCTAssertEqual(document.body.meta, TestPageMetadata(total: 70, limit: 40, offset: 10))
 		XCTAssertEqual(document.body.links?.link.url, "https://website.com")
@@ -695,8 +695,8 @@ extension DocumentTests {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.value.id.rawValue, "1")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.value.id.rawValue, "1")
 		XCTAssertEqual(document.body.includes?.count, 0)
 		XCTAssertEqual(document.body.meta, TestPageMetadata(total: 70, limit: 40, offset: 10))
 		XCTAssertEqual(document.body.links?.link.url, "https://website.com")
@@ -726,8 +726,8 @@ extension DocumentTests {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.value.id.rawValue, "1")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.value.id.rawValue, "1")
 		XCTAssertEqual(document.body.includes?.count, 1)
 		XCTAssertEqual(document.body.includes?[Author.self].count, 1)
 		XCTAssertEqual(document.body.includes?[Author.self][0].id.rawValue, "33")
@@ -744,8 +744,8 @@ extension DocumentTests {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.value.id.rawValue, "1")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.value.id.rawValue, "1")
 		XCTAssertEqual(document.body.includes?.count, 1)
 		XCTAssertEqual(document.body.includes?[Author.self].count, 1)
 		XCTAssertEqual(document.body.includes?[Author.self][0].id.rawValue, "33")
@@ -763,8 +763,8 @@ extension DocumentTests {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.value.id.rawValue, "1")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.value.id.rawValue, "1")
 		XCTAssertEqual(document.body.includes?.count, 1)
 		XCTAssertEqual(document.body.includes?[Author.self].count, 1)
 		XCTAssertEqual(document.body.includes?[Author.self][0].id.rawValue, "33")
@@ -782,8 +782,8 @@ extension DocumentTests {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.value.id.rawValue, "1")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.value.id.rawValue, "1")
 		XCTAssertEqual(document.body.includes?.count, 1)
 		XCTAssertEqual(document.body.includes?[Author.self].count, 1)
 		XCTAssertEqual(document.body.includes?[Author.self][0].id.rawValue, "33")
@@ -802,8 +802,8 @@ extension DocumentTests {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.value.id.rawValue, "1")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.value.id.rawValue, "1")
 		XCTAssertEqual(document.body.meta, TestPageMetadata(total: 70, limit: 40, offset: 10))
 		XCTAssertEqual(document.body.links?.link.url, "https://website.com")
 		XCTAssertEqual(document.body.links?.link.meta, NoMetadata())
@@ -825,8 +825,8 @@ extension DocumentTests {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.value.id.rawValue, "1")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.value.id.rawValue, "1")
 		XCTAssertEqual(document.body.meta, TestPageMetadata(total: 70, limit: 40, offset: 10))
 		XCTAssertEqual(document.body.links?.link.url, "https://website.com")
 		XCTAssertEqual(document.body.links?.link.meta, NoMetadata())
@@ -850,8 +850,8 @@ extension DocumentTests {
 		let article = Article(id: Id(rawValue: "1"), attributes: .none, relationships: .init(author: ToOneRelationship(id: Id(rawValue: "33"))), meta: .none, links: .none)
 		let document = decoded(type: Document<SingleResourceBody<Poly2<Article, Author>>, NoMetadata, NoLinks, NoIncludes, NoAPIDescription, UnknownJSONAPIError>.self, data: single_document_no_includes)
 
-		XCTAssertEqual(document.body.primaryData?.value[Article.self], article)
-		XCTAssertNil(document.body.primaryData?.value[Author.self])
+		XCTAssertEqual(document.body.primaryResource?.value[Article.self], article)
+		XCTAssertNil(document.body.primaryResource?.value[Author.self])
 	}
 
 	func test_singleDocument_PolyPrimaryResource_encode() {
@@ -862,8 +862,8 @@ extension DocumentTests {
 		let article = Article(id: Id(rawValue: "1"), attributes: .none, relationships: .init(author: ToOneRelationship(id: Id(rawValue: "33"))), meta: .none, links: .none)
 		let document = decoded(type: Document<SingleResourceBody<Poly2<Article, Author>>, NoMetadata, NoLinks, NoIncludes, TestAPIDescription, UnknownJSONAPIError>.self, data: single_document_no_includes_with_api_description)
 
-		XCTAssertEqual(document.body.primaryData?.value[Article.self], article)
-		XCTAssertNil(document.body.primaryData?.value[Author.self])
+		XCTAssertEqual(document.body.primaryResource?.value[Article.self], article)
+		XCTAssertNil(document.body.primaryResource?.value[Author.self])
 		XCTAssertEqual(document.apiDescription.version, "1.0")
 	}
 
@@ -880,11 +880,11 @@ extension DocumentTests {
 		
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.values.count, 3)
-		XCTAssertEqual(document.body.primaryData?.values[0].id.rawValue, "1")
-		XCTAssertEqual(document.body.primaryData?.values[1].id.rawValue, "2")
-		XCTAssertEqual(document.body.primaryData?.values[2].id.rawValue, "3")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.values.count, 3)
+		XCTAssertEqual(document.body.primaryResource?.values[0].id.rawValue, "1")
+		XCTAssertEqual(document.body.primaryResource?.values[1].id.rawValue, "2")
+		XCTAssertEqual(document.body.primaryResource?.values[2].id.rawValue, "3")
 		XCTAssertEqual(document.body.includes?.count, 0)
 	}
 
@@ -899,11 +899,11 @@ extension DocumentTests {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.values.count, 3)
-		XCTAssertEqual(document.body.primaryData?.values[0].id.rawValue, "1")
-		XCTAssertEqual(document.body.primaryData?.values[1].id.rawValue, "2")
-		XCTAssertEqual(document.body.primaryData?.values[2].id.rawValue, "3")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.values.count, 3)
+		XCTAssertEqual(document.body.primaryResource?.values[0].id.rawValue, "1")
+		XCTAssertEqual(document.body.primaryResource?.values[1].id.rawValue, "2")
+		XCTAssertEqual(document.body.primaryResource?.values[2].id.rawValue, "3")
 		XCTAssertEqual(document.body.includes?.count, 0)
 		XCTAssertEqual(document.apiDescription.version, "1.0")
 	}
@@ -919,11 +919,11 @@ extension DocumentTests {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.values.count, 3)
-		XCTAssertEqual(document.body.primaryData?.values[0].id.rawValue, "1")
-		XCTAssertEqual(document.body.primaryData?.values[1].id.rawValue, "2")
-		XCTAssertEqual(document.body.primaryData?.values[2].id.rawValue, "3")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.values.count, 3)
+		XCTAssertEqual(document.body.primaryResource?.values[0].id.rawValue, "1")
+		XCTAssertEqual(document.body.primaryResource?.values[1].id.rawValue, "2")
+		XCTAssertEqual(document.body.primaryResource?.values[2].id.rawValue, "3")
 		XCTAssertEqual(document.body.includes?.count, 3)
 		XCTAssertEqual(document.body.includes?[Author.self].count, 3)
 		XCTAssertEqual(document.body.includes?[Author.self][0].id.rawValue, "33")
@@ -942,11 +942,11 @@ extension DocumentTests {
 
 		XCTAssertFalse(document.body.isError)
 		XCTAssertNil(document.body.errors)
-		XCTAssertNotNil(document.body.primaryData)
-		XCTAssertEqual(document.body.primaryData?.values.count, 3)
-		XCTAssertEqual(document.body.primaryData?.values[0].id.rawValue, "1")
-		XCTAssertEqual(document.body.primaryData?.values[1].id.rawValue, "2")
-		XCTAssertEqual(document.body.primaryData?.values[2].id.rawValue, "3")
+		XCTAssertNotNil(document.body.primaryResource)
+		XCTAssertEqual(document.body.primaryResource?.values.count, 3)
+		XCTAssertEqual(document.body.primaryResource?.values[0].id.rawValue, "1")
+		XCTAssertEqual(document.body.primaryResource?.values[1].id.rawValue, "2")
+		XCTAssertEqual(document.body.primaryResource?.values[2].id.rawValue, "3")
 		XCTAssertEqual(document.body.includes?.count, 3)
 		XCTAssertEqual(document.body.includes?[Author.self].count, 3)
 		XCTAssertEqual(document.body.includes?[Author.self][0].id.rawValue, "33")

Tests/JSONAPITests/Entity/EntityTests.swift

@@ -26,7 +26,10 @@ class EntityTests: XCTestCase {
 	}
 
 	func test_optional_relationship_operator_access() {
-		
+		let entity1 = TestEntity1(attributes: .none, relationships: .none, meta: .none, links: .none)
+		let entity = TestEntity9(attributes: .none, relationships: .init(one: entity1.pointer, nullableOne: .init(entity: entity1, meta: .none, links: .none), optionalOne: .init(entity: entity1, meta: .none, links: .none), optionalNullableOne: nil, optionalMany: .init(entities: [entity1, entity1], meta: .none, links: .none)), meta: .none, links: .none)
+
+		XCTAssertEqual(entity ~> \.optionalOne, entity1.id)
 	}
 	
 	func test_toMany_relationship_operator_access() {
@@ -39,7 +42,10 @@ class EntityTests: XCTestCase {
 	}
 
 	func test_optionalToMany_relationship_opeartor_access() {
+		let entity1 = TestEntity1(attributes: .none, relationships: .none, meta: .none, links: .none)
+		let entity = TestEntity9(attributes: .none, relationships: .init(one: entity1.pointer, nullableOne: .init(entity: entity1, meta: .none, links: .none), optionalOne: nil, optionalNullableOne: nil, optionalMany: .init(entities: [entity1, entity1], meta: .none, links: .none)), meta: .none, links: .none)
 
+		XCTAssertEqual(entity ~> \.optionalMany, [entity1.id, entity1.id])
 	}
 	
 	func test_relationshipIds() {
@@ -59,6 +65,12 @@ class EntityTests: XCTestCase {
 		XCTAssertEqual(pointer.links.link1.url, "ok")
 	}
 
+	func test_unidentifiedEntityAttributeAccess() {
+		let entity = UnidentifiedTestEntity(attributes: .init(me: "hello"), relationships: .none, meta: .none, links: .none)
+
+		XCTAssertEqual(entity[\.me], "hello")
+	}
+
 	func test_initialization() {
 		let entity1 = TestEntity1(id: .init(rawValue: "wow"), attributes: .none, relationships: .none, meta: .none, links: .none)
 		let entity2 = TestEntity2(id: .init(rawValue: "cool"), attributes: .none, relationships: .init(other: .init(entity: entity1)), meta: .none, links: .none)
@@ -73,6 +85,7 @@ class EntityTests: XCTestCase {
 		XCTAssertNoThrow(try TestEntity8(id: .init(rawValue: "8"), attributes: .init(string: .init(value: "hello"), int: .init(value: 10), stringFromInt: .init(rawValue: 20), plus: .init(rawValue: 30), doubleFromInt: .init(rawValue: 32), omitted: nil, nullToString: .init(rawValue: nil)), relationships: .none, meta: .none, links: .none))
 		let _ = TestEntity9(id: .init(rawValue: "9"), attributes: .none, relationships: .init(one: entity1.pointer, nullableOne: nil, optionalOne: nil, optionalNullableOne: nil, optionalMany: nil), meta: .none, links: .none)
 		let _ = TestEntity9(id: .init(rawValue: "9"), attributes: .none, relationships: .init(one: entity1.pointer, nullableOne: .init(entity: nil), optionalOne: nil, optionalNullableOne: nil, optionalMany: nil), meta: .none, links: .none)
+		let _ = TestEntity9(id: .init(rawValue: "9"), attributes: .none, relationships: .init(one: entity1.pointer, nullableOne: .init(id: nil), optionalOne: nil, optionalNullableOne: nil, optionalMany: nil), meta: .none, links: .none)
 		let _ = TestEntity9(id: .init(rawValue: "9"), attributes: .none, relationships: .init(one: entity1.pointer, nullableOne: .init(entity: entity1, meta: .none, links: .none), optionalOne: nil, optionalNullableOne: nil, optionalMany: nil), meta: .none, links: .none)
 		let _ = TestEntity9(id: .init(rawValue: "9"), attributes: .none, relationships: .init(one: entity1.pointer, nullableOne: nil, optionalOne: entity1.pointer, optionalNullableOne: nil, optionalMany: nil), meta: .none, links: .none)
 		let _ = TestEntity9(id: .init(rawValue: "9"), attributes: .none, relationships: .init(one: entity1.pointer, nullableOne: nil, optionalOne: nil, optionalNullableOne: .init(entity: entity1, meta: .none, links: .none), optionalMany: nil), meta: .none, links: .none)
@@ -88,6 +101,36 @@ class EntityTests: XCTestCase {
 	}
 }
 
+// MARK: - Identifying entity copies
+extension EntityTests {
+	func test_copyIdentifiedByType() {
+		let unidentifiedEntity = UnidentifiedTestEntity(attributes: .init(me: .init(value: "hello")), relationships: .none, meta: .none, links: .none)
+
+		let identifiedCopy = unidentifiedEntity.identified(byType: String.self)
+
+		XCTAssertEqual(unidentifiedEntity.attributes, identifiedCopy.attributes)
+		XCTAssertEqual(unidentifiedEntity.relationships, identifiedCopy.relationships)
+	}
+
+	func test_copyIdentifiedByValue() {
+		let unidentifiedEntity = UnidentifiedTestEntity(attributes: .init(me: .init(value: "hello")), relationships: .none, meta: .none, links: .none)
+
+		let identifiedCopy = unidentifiedEntity.identified(by: "hello")
+
+		XCTAssertEqual(unidentifiedEntity.attributes, identifiedCopy.attributes)
+		XCTAssertEqual(unidentifiedEntity.relationships, identifiedCopy.relationships)
+		XCTAssertEqual(identifiedCopy.id, "hello")
+	}
+
+	func test_copyWithNewId() {
+		let identifiedEntity = TestEntity1(attributes: .none, relationships: .none, meta: .none, links: .none)
+
+		let identifiedCopy = identifiedEntity.withNewIdentifier()
+
+		XCTAssertNotEqual(identifiedEntity.id, identifiedCopy.id)
+	}
+}
+
 // MARK: - Encode/Decode
 extension EntityTests {
 
@@ -98,6 +141,8 @@ extension EntityTests {
 		XCTAssert(type(of: entity.relationships) == NoRelationships.self)
 		XCTAssert(type(of: entity.attributes) == NoAttributes.self)
 		XCTAssertNoThrow(try TestEntity1.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_EntityNoRelationshipsNoAttributes_encode() {
@@ -113,6 +158,8 @@ extension EntityTests {
 
 		XCTAssertEqual(entity[\.floater], 123.321)
 		XCTAssertNoThrow(try TestEntity5.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_EntityNoRelationshipsSomeAttributes_encode() {
@@ -128,6 +175,8 @@ extension EntityTests {
 		
 		XCTAssertEqual((entity ~> \.others).map { $0.rawValue }, ["364B3B69-4DF1-467F-B52E-B0C9E44F666E"])
 		XCTAssertNoThrow(try TestEntity3.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_EntitySomeRelationshipsNoAttributes_encode() {
@@ -143,6 +192,8 @@ extension EntityTests {
 		XCTAssertEqual(entity[\.number], 992299)
 		XCTAssertEqual((entity ~> \.other).rawValue, "2DF03B69-4B0A-467F-B52E-B0C9E44FCECF")
 		XCTAssertNoThrow(try TestEntity4.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_EntitySomeRelationshipsSomeAttributes_encode() {
@@ -162,6 +213,8 @@ extension EntityTests {
 		XCTAssertNil(entity[\.maybeHere])
 		XCTAssertEqual(entity[\.maybeNull], "World")
 		XCTAssertNoThrow(try TestEntity6.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_entityOneOmittedAttribute_encode() {
@@ -177,6 +230,8 @@ extension EntityTests {
 		XCTAssertEqual(entity[\.maybeHere], "World")
 		XCTAssertNil(entity[\.maybeNull])
 		XCTAssertNoThrow(try TestEntity6.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_entityOneNullAttribute_encode() {
@@ -192,6 +247,8 @@ extension EntityTests {
 		XCTAssertEqual(entity[\.maybeHere], "World")
 		XCTAssertEqual(entity[\.maybeNull], "!")
 		XCTAssertNoThrow(try TestEntity6.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_entityAllAttribute_encode() {
@@ -208,7 +265,7 @@ extension EntityTests {
 		XCTAssertNil(entity[\.maybeNull])
 		XCTAssertNoThrow(try TestEntity6.check(entity))
 
-		print(encodable: entity)
+		testEncoded(entity: entity)
 	}
 
 	func test_entityOneNullAndOneOmittedAttribute_encode() {
@@ -229,7 +286,7 @@ extension EntityTests {
 		XCTAssertNil(entity[\.maybeHereMaybeNull])
 		XCTAssertNoThrow(try TestEntity7.check(entity))
 
-		print(encodable: entity)
+		testEncoded(entity: entity)
 	}
 
 	func test_NullOptionalNullableAttribute_encode() {
@@ -244,6 +301,8 @@ extension EntityTests {
 		XCTAssertEqual(entity[\.here], "Hello")
 		XCTAssertEqual(entity[\.maybeHereMaybeNull], "World")
 		XCTAssertNoThrow(try TestEntity7.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_NonNullOptionalNullableAttribute_encode() {
@@ -265,6 +324,8 @@ extension EntityTests {
 		XCTAssertEqual(entity[\.doubleFromInt], 22.0)
 		XCTAssertEqual(entity[\.nullToString], "nil")
 		XCTAssertNoThrow(try TestEntity8.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_IntToString_encode() {
@@ -299,6 +360,8 @@ extension EntityTests {
 		XCTAssertNil(entity ~> \.optionalOne)
 		XCTAssertEqual((entity ~> \.optionalNullableOne)?.rawValue, "1229")
 		XCTAssertNoThrow(try TestEntity9.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_nullableRelationshipNotNullOrOmitted_encode() {
@@ -314,6 +377,8 @@ extension EntityTests {
 		XCTAssertEqual((entity ~> \.one).rawValue, "4459")
 		XCTAssertNil(entity ~> \.optionalNullableOne)
 		XCTAssertNoThrow(try TestEntity9.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_nullableRelationshipNotNull_encode() {
@@ -329,6 +394,8 @@ extension EntityTests {
 		XCTAssertEqual((entity ~> \.one).rawValue, "4459")
 		XCTAssertNil(entity ~> \.optionalNullableOne)
 		XCTAssertNoThrow(try TestEntity9.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_optionalNullableRelationshipNulled_encode() {
@@ -344,6 +411,8 @@ extension EntityTests {
 		XCTAssertEqual((entity ~> \.one).rawValue, "4452")
 		XCTAssertNil(entity ~> \.optionalNullableOne)
 		XCTAssertNoThrow(try TestEntity9.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_nullableRelationshipIsNull_encode() {
@@ -360,6 +429,8 @@ extension EntityTests {
 		XCTAssertEqual((entity ~> \.optionalMany)?[0].rawValue, "332223")
 		XCTAssertNil(entity ~> \.optionalNullableOne)
 		XCTAssertNoThrow(try TestEntity9.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_optionalToManyIsNotOmitted_encode() {
@@ -377,6 +448,8 @@ extension EntityTests {
 
 		XCTAssertEqual((entity ~> \.selfRef).rawValue, "1")
 		XCTAssertNoThrow(try TestEntity10.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_RleationshipsOfSameType_encode() {
@@ -395,6 +468,8 @@ extension EntityTests {
 		XCTAssertNil(entity[\.me])
 		XCTAssertEqual(entity.id, .unidentified)
 		XCTAssertNoThrow(try UnidentifiedTestEntity.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_UnidentifiedEntity_encode() {
@@ -409,6 +484,8 @@ extension EntityTests {
 		XCTAssertEqual(entity[\.me], "unknown")
 		XCTAssertEqual(entity.id, .unidentified)
 		XCTAssertNoThrow(try UnidentifiedTestEntity.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_UnidentifiedEntityWithAttributes_encode() {
@@ -429,6 +506,8 @@ extension EntityTests {
 		XCTAssertEqual(entity.meta.x, "world")
 		XCTAssertEqual(entity.meta.y, 5)
 		XCTAssertNoThrow(try UnidentifiedTestEntityWithMeta.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_UnidentifiedEntityWithAttributesAndMeta_encode() {
@@ -444,6 +523,8 @@ extension EntityTests {
 		XCTAssertEqual(entity.id, .unidentified)
 		XCTAssertEqual(entity.links.link1, .init(url: "https://image.com/image.png"))
 		XCTAssertNoThrow(try UnidentifiedTestEntityWithLinks.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_UnidentifiedEntityWithAttributesAndLinks_encode() {
@@ -461,6 +542,8 @@ extension EntityTests {
 		XCTAssertEqual(entity.meta.y, 5)
 		XCTAssertEqual(entity.links.link1, .init(url: "https://image.com/image.png"))
 		XCTAssertNoThrow(try UnidentifiedTestEntityWithMetaAndLinks.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_UnidentifiedEntityWithAttributesAndMetaAndLinks_encode() {
@@ -478,6 +561,8 @@ extension EntityTests {
 		XCTAssertEqual(entity.meta.x, "world")
 		XCTAssertEqual(entity.meta.y, 5)
 		XCTAssertNoThrow(try TestEntity4WithMeta.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_EntitySomeRelationshipsSomeAttributesWithMeta_encode() {
@@ -494,6 +579,8 @@ extension EntityTests {
 		XCTAssertEqual((entity ~> \.other).rawValue, "2DF03B69-4B0A-467F-B52E-B0C9E44FCECF")
 		XCTAssertEqual(entity.links.link1, .init(url: "https://image.com/image.png"))
 		XCTAssertNoThrow(try TestEntity4WithLinks.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_EntitySomeRelationshipsSomeAttributesWithLinks_encode() {
@@ -512,6 +599,8 @@ extension EntityTests {
 		XCTAssertEqual(entity.meta.y, 5)
 		XCTAssertEqual(entity.links.link1, .init(url: "https://image.com/image.png"))
 		XCTAssertNoThrow(try TestEntity4WithMetaAndLinks.check(entity))
+
+		testEncoded(entity: entity)
 	}
 
 	func test_EntitySomeRelationshipsSomeAttributesWithMetaAndLinks_encode() {

Tests/JSONAPITests/Poly/PolyProxyTests.swift

@@ -23,6 +23,7 @@ public class PolyProxyTests: XCTestCase {
 		XCTAssertEqual(polyUserA[\.name], "Ken Moore")
 		XCTAssertEqual(polyUserA.id, "1")
 		XCTAssertEqual(polyUserA.relationships, .none)
+		XCTAssertEqual(polyUserA[\.x], .init(x: "y"))
 	}
 
 	func test_UserAAndBEncodeEquality() {
@@ -57,6 +58,7 @@ public class PolyProxyTests: XCTestCase {
 		XCTAssertEqual(polyUserB[\.name], "Ken Less")
 		XCTAssertEqual(polyUserB.id, "2")
 		XCTAssertEqual(polyUserB.relationships, .none)
+		XCTAssertEqual(polyUserB[\.x], .init(x: "y"))
 	}
 }
 
@@ -111,9 +113,9 @@ extension Poly2: EntityProxy, JSONTyped where A == PolyProxyTests.UserA, B == Po
 	public var attributes: SharedUserDescription.Attributes {
 		switch self {
 		case .a(let a):
-			return .init(name: .init(value: "\(a[\.firstName]) \(a[\.lastName])"))
+			return .init(name: .init(value: "\(a[\.firstName]) \(a[\.lastName])"), x: .init(x: "y"))
 		case .b(let b):
-			return .init(name: .init(value: b[\.name].joined(separator: " ")))
+			return .init(name: .init(value: b[\.name].joined(separator: " ")), x: .init(x: "y"))
 		}
 	}
 
@@ -121,14 +123,19 @@ extension Poly2: EntityProxy, JSONTyped where A == PolyProxyTests.UserA, B == Po
 		return .none
 	}
 
-	public enum SharedUserDescription: EntityDescription {
+	public enum SharedUserDescription: EntityProxyDescription {
 		public static var type: String { return A.type }
 
-		public struct Attributes: JSONAPI.Attributes {
+		public struct Attributes: Equatable {
 			let name: Attribute<String>
+			let x: SomeRandomThingThatIsNotCodable
 		}
 
 		public typealias Relationships = NoRelationships
+
+		public struct SomeRandomThingThatIsNotCodable: Equatable {
+			let x: String
+		}
 	}
 
 	public typealias Description = SharedUserDescription

Tests/JSONAPITests/Test Helpers/EncodedAttributeTest.swift

@@ -0,0 +1,34 @@
+//
+//  EncodedAttributeTest.swift
+//  JSONAPITests
+//
+//  Created by Mathew Polzin on 12/21/18.
+//
+
+import Foundation
+import XCTest
+@testable import JSONAPI
+import JSONAPITestLib
+
+private struct Wrapper<Value: Equatable & Codable, Transform: Transformer>: Codable where Value == Transform.From {
+	let x: TransformedAttribute<Value, Transform>
+
+	init(x: TransformedAttribute<Value, Transform>) {
+		self.x = x
+	}
+}
+
+/// This function attempts to just cast to the type, so it only works
+/// for Attributes of primitive types (primitive to JSON).
+func testEncodedPrimitive<Value: Equatable & Codable, Transform: Transformer>(attribute: TransformedAttribute<Value, Transform>) {
+	let encodedAttributeData = encoded(value: Wrapper<Value, Transform>(x: attribute))
+	let wrapperObject = try! JSONSerialization.jsonObject(with: encodedAttributeData, options: []) as! [String: Any]
+	let jsonObject = wrapperObject["x"]
+
+	guard let jsonAttribute = jsonObject as? Transform.From else {
+		XCTFail("Attribute did not encode to the correct type")
+		return
+	}
+
+	XCTAssertEqual(attribute.rawValue, jsonAttribute)
+}

Tests/JSONAPITests/Test Helpers/EncodedEntityPropertyTest.swift

@@ -0,0 +1,63 @@
+//
+//  EncodedEntityPropertyTest.swift
+//  JSONAPITests
+//
+//  Created by Mathew Polzin on 12/21/18.
+//
+
+import Foundation
+import XCTest
+import JSONAPI
+import JSONAPITestLib
+
+func testEncoded<E: EntityType>(entity: E) {
+	let encodedEntityData = encoded(value: entity)
+	let jsonObject = try! JSONSerialization.jsonObject(with: encodedEntityData, options: [])
+	let jsonDict = jsonObject as? [String: Any]
+
+	XCTAssertNotNil(jsonDict)
+
+	let jsonId = jsonDict?["id"]
+
+	if E.EntityRawIdType.self == Unidentified.self {
+		XCTAssertNil(jsonId)
+	} else {
+		XCTAssertNotNil(jsonId)
+	}
+
+	let jsonType = jsonDict?["type"] as? String
+
+	XCTAssertEqual(jsonType, E.type)
+
+	let jsonAttributes = jsonDict?["attributes"] as? [String: Any]
+
+	if E.Attributes.self == NoAttributes.self {
+		XCTAssertNil(jsonAttributes)
+	} else {
+		XCTAssertNotNil(jsonAttributes)
+	}
+
+	let jsonRelationships = jsonDict?["relationships"] as? [String: Any]
+
+	if E.Relationships.self == NoRelationships.self {
+		XCTAssertNil(jsonRelationships)
+	} else {
+		XCTAssertNotNil(jsonRelationships)
+	}
+
+	let jsonMeta = jsonDict?["meta"] as? [String: Any]
+
+	if E.Meta.self == NoMetadata.self {
+		XCTAssertNil(jsonMeta)
+	} else {
+		XCTAssertNotNil(jsonMeta)
+	}
+
+	let jsonLinks = jsonDict?["links"] as? [String: Any]
+
+	if E.Links.self == NoLinks.self {
+		XCTAssertNil(jsonLinks)
+	} else {
+		XCTAssertNotNil(jsonLinks)
+	}
+}

Tests/JSONAPITests/XCTestManifests.swift

@@ -15,6 +15,7 @@ extension AttributeTests {
     static let __allTests = [
         ("test_AttributeIsTransformedAttribute", test_AttributeIsTransformedAttribute),
         ("test_AttributeNonThrowingConstructor", test_AttributeNonThrowingConstructor),
+        ("test_EncodedPrimitives", test_EncodedPrimitives),
         ("test_NullableIsEqualToNonNullableIfNotNil", test_NullableIsEqualToNonNullableIfNotNil),
         ("test_NullableIsNullIfNil", test_NullableIsNullIfNil),
         ("test_TransformedAttributeNoThrow", test_TransformedAttributeNoThrow),
@@ -181,6 +182,9 @@ extension EntityCheckTests {
 
 extension EntityTests {
     static let __allTests = [
+        ("test_copyIdentifiedByType", test_copyIdentifiedByType),
+        ("test_copyIdentifiedByValue", test_copyIdentifiedByValue),
+        ("test_copyWithNewId", test_copyWithNewId),
         ("test_entityAllAttribute", test_entityAllAttribute),
         ("test_entityAllAttribute_encode", test_entityAllAttribute_encode),
         ("test_entityBrokenNullableOmittedAttribute", test_entityBrokenNullableOmittedAttribute),
@@ -235,6 +239,7 @@ extension EntityTests {
         ("test_toMany_relationship_operator_access", test_toMany_relationship_operator_access),
         ("test_UnidentifiedEntity", test_UnidentifiedEntity),
         ("test_UnidentifiedEntity_encode", test_UnidentifiedEntity_encode),
+        ("test_unidentifiedEntityAttributeAccess", test_unidentifiedEntityAttributeAccess),
         ("test_UnidentifiedEntityWithAttributes", test_UnidentifiedEntityWithAttributes),
         ("test_UnidentifiedEntityWithAttributes_encode", test_UnidentifiedEntityWithAttributes_encode),
         ("test_UnidentifiedEntityWithAttributesAndLinks", test_UnidentifiedEntityWithAttributesAndLinks),