Added check for nullable array attributes

README.md

@@ -76,7 +76,7 @@ To create an Xcode project for JSONAPI, run
 - [x] `meta`
 
 ### Entity Validator (using reflection)
-- [ ] Disallow optional array in `Attribute` and `Relationship` (should be empty array, not `null`).
+- [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 `ToManyRelationship` and `ToOneRelationship` within `Relationships` struct.
 

Sources/JSONAPITestLib/EntityCheck.swift

@@ -10,8 +10,9 @@ import JSONAPI
 public enum EntityCheckError: Swift.Error {
 	case attributesNotStruct
 	case relationshipsNotStruct
-	case badAttribute(named: String)
-	case badRelationship(named: String)
+	case nonAttribute(named: String)
+	case nonRelationship(named: String)
+	case nullArray(named: String)
 	case badId
 }
 
@@ -19,10 +20,18 @@ public struct EntityCheckErrors: Swift.Error {
 	let problems: [EntityCheckError]
 }
 
-public protocol OptionalAttributeType {}
-
+private protocol OptionalAttributeType {}
 extension Optional: OptionalAttributeType where Wrapped: AttributeType {}
 
+private protocol OptionalArray {}
+extension Optional: OptionalArray where Wrapped: ArrayType {}
+
+private protocol AttributeTypeWithOptionalArray {}
+extension TransformedAttribute: AttributeTypeWithOptionalArray where RawValue: OptionalArray {}
+
+private protocol OptionalRelationshipType {}
+extension Optional: OptionalRelationshipType where Wrapped: RelationshipType {}
+
 public extension Entity {
 	public static func check(_ entity: Entity) throws {
 		var problems = [EntityCheckError]()
@@ -40,7 +49,10 @@ public extension Entity {
 		for attribute in attributesMirror.children {
 			if attribute.value as? AttributeType == nil,
 				attribute.value as? OptionalAttributeType == nil {
-				problems.append(.badAttribute(named: attribute.label ?? "unnamed"))
+				problems.append(.nonAttribute(named: attribute.label ?? "unnamed"))
+			}
+			if attribute.value as? AttributeTypeWithOptionalArray != nil {
+				problems.append(.nullArray(named: attribute.label ?? "unnamed"))
 			}
 		}
 
@@ -52,7 +64,7 @@ public extension Entity {
 
 		for relationship in relationshipsMirror.children {
 			if relationship.value as? RelationshipType == nil {
-				problems.append(.badRelationship(named: relationship.label ?? "unnamed"))
+				problems.append(.nonRelationship(named: relationship.label ?? "unnamed"))
 			}
 		}
 

Tests/JSONAPITests/TestLib/EntityCheckTests.swift

@@ -36,6 +36,11 @@ class EntityCheckTests: XCTestCase {
 		let entity = BadRelationshipEntity(relationships: .init(x: OkEntity().pointer, y: OkEntity().id))
 		XCTAssertThrowsError(try BadRelationshipEntity.check(entity))
 	}
+
+	func test_failsWithOptionalArrayAttribute() {
+		let entity = OptionalArrayAttributeEntity(attributes: .init(x: ["hello"], y: nil))
+		XCTAssertThrowsError(try OptionalArrayAttributeEntity.check(entity))
+	}
 }
 
 // MARK: - Test types
@@ -121,4 +126,17 @@ extension EntityCheckTests {
 	}
 
 	public typealias BadRelationshipEntity = Entity<BadRelationshipDescription>
+
+	enum OptionalArrayAttributeDescription: EntityDescription {
+		public static var type: String { return "hello" }
+
+		public struct Attributes: JSONAPI.Attributes {
+			let x: Attribute<[String]>
+			let y: Attribute<[String]?>
+		}
+
+		public typealias Relationships = NoRelationships
+	}
+
+	public typealias OptionalArrayAttributeEntity = Entity<OptionalArrayAttributeDescription>
 }

Tests/JSONAPITests/XCTestManifests.swift

@@ -74,6 +74,7 @@ extension EntityCheckTests {
         ("test_failsWithBadRelationship", test_failsWithBadRelationship),
         ("test_failsWithEnumAttributes", test_failsWithEnumAttributes),
         ("test_failsWithEnumRelationships", test_failsWithEnumRelationships),
+        ("test_failsWithOptionalArrayAttribute", test_failsWithOptionalArrayAttribute),
     ]
 }