Delete @singleton macro. The value is too murky given the complexity …

…of the system

Sources/SafeDI/ExternalMacros.swift

@@ -23,9 +23,9 @@
 
 #else
 
-/// Marks a `class`, `struct`, or `actor` as capable of having properties that conform to this type decorated with `@Instantiated` or `@Singleton`.
+/// Marks a `class`, `struct`, or `actor` as capable of having properties that conform to this type decorated with `@Instantiated`
 ///
-/// - Parameter fulfillingAdditionalTypes: The types (in addition to the type decorated with this macro) that can be decorated with `@Instantiated` or `@Singleton` and yield a result of this type. The types provided *must* be either superclasses of this type or protocols to which this type conforms.
+/// - Parameter fulfillingAdditionalTypes: The types (in addition to the type decorated with this macro) that can be decorated with `@Instantiated` and yield a result of this type. The types provided *must* be either superclasses of this type or protocols to which this type conforms.
 @attached(member, names: arbitrary) public macro Instantiable(fulfillingAdditionalTypes: [Any.Type] = []) = #externalMacro(module: "SafeDIMacros", type: "InstantiableMacro")
 
 /// Marks a SafeDI dependency that is instantiated when its parent object is instantiated.
@@ -34,9 +34,6 @@
 /// Marks a SafeDI dependency that is instantiated by an object higher up in the dependency tree.
 @attached(peer) public macro Inherited() = #externalMacro(module: "SafeDIMacros", type: "InjectableMacro")
 
-/// Marks a SafeDI dependency that will only ever have one instance instantiated at a given time. Singleton dependencies may deallocate when all of the objects that use it deallocate. Singleton dependencies can not be marked with @Instantiated.
-@attached(peer) public macro Singleton() = #externalMacro(module: "SafeDIMacros", type: "InjectableMacro")
-
 /// Marks a SafeDI dependency that is injected into the parent object's initializer and forwarded to objects further down in the dependency tree.
 @attached(peer) public macro Forwarded() = #externalMacro(module: "SafeDIMacros", type: "InjectableMacro")
 

Sources/SafeDICore/Errors/DependencyTreeGeneratorError.swift

@@ -22,17 +22,14 @@ enum DependencyTreeGeneratorError: Error, CustomStringConvertible {
 
  case noInstantiableFound(TypeDescription)
  case noRootInstantiableFound
- case unsatisfiableSingletons([Property], roots: [TypeDescription])
  case unfulfillableProperties([UnfulfillableProperty])
 
  var description: String {
  switch self {
  case let .noInstantiableFound(typeDescription):
- "No `@\(InstantiableVisitor.macroName)`-decorated type found to fulfill `@\(Dependency.Source.instantiated.rawValue)`, `@\(Dependency.Source.lazyInstantiated.rawValue)`, or `@\(Dependency.Source.singleton.rawValue)`-decorated property with type '\(typeDescription.asSource)'"
+ "No `@\(InstantiableVisitor.macroName)`-decorated type found to fulfill `@\(Dependency.Source.instantiated.rawValue)` or  `@\(Dependency.Source.lazyInstantiated.rawValue)`-decorated property with type '\(typeDescription.asSource)'"
  case .noRootInstantiableFound:
- "All `@\(InstantiableVisitor.macroName)`-decorated types were found on a @\(Dependency.Source.instantiated.rawValue)`, `@\(Dependency.Source.lazyInstantiated.rawValue)`, or `@\(Dependency.Source.singleton.rawValue)`-decorated property. There must be at least one `@\(InstantiableVisitor.macroName)`-decorated types that is not instantiated by another `@\(InstantiableVisitor.macroName)`-decorated type"
- case let .unsatisfiableSingletons(properties, roots):
- "All `@\(Dependency.Source.singleton.rawValue)`-decorated properties must be in the same dependency tree to ensure they are singletons. Found multiple root `@\(InstantiableVisitor.macroName)`-decorated types: \(roots.map(\.asSource).joined(separator: ", ")). The following `@\(Dependency.Source.singleton.rawValue)`-decorated properties were found across multiple roots: \(properties.map(\.asSource).joined(separator: ", "))."
+ "All `@\(InstantiableVisitor.macroName)`-decorated types were found on a @\(Dependency.Source.instantiated.rawValue)` or `@\(Dependency.Source.lazyInstantiated.rawValue)`-decorated property. There must be at least one `@\(InstantiableVisitor.macroName)`-decorated types that is not instantiated by another `@\(InstantiableVisitor.macroName)`-decorated type"
  case let .unfulfillableProperties(unfulfillableProperties):
  """
  The following inherited properties were never instantiated:

Sources/SafeDICore/Errors/FixableInstantiableError.swift

@@ -29,7 +29,7 @@ public enum FixableInstantiableError: DiagnosticError {
  public var description: String {
  switch self {
  case .dependencyHasTooManyAttributes:
- return "Dependency can have at most one of @\(Dependency.Source.instantiated), @\(Dependency.Source.inherited), @\(Dependency.Source.singleton), or @\(Dependency.Source.forwarded) attached macro"
+ return "Dependency can have at most one of @\(Dependency.Source.instantiated), @\(Dependency.Source.inherited), or @\(Dependency.Source.forwarded) attached macro"
  case .dependencyHasInitializer:
  return "Dependency must not have hand-written initializer"
  case .missingPublicOrOpenAttribute:

Sources/SafeDICore/Generators/DependencyTreeGenerator.swift

@@ -35,10 +35,8 @@ public final class DependencyTreeGenerator {
  public func generate() async throws -> String {
  try validateReachableTypeDescriptions()
  try validateAtLeastOneRootFound()
- // showstopper TODO: Validate that all @Singleton properties are never @Constructed (or @Inherited??)
 
  let typeDescriptionToScopeMap = try createTypeDescriptionToScopeMapping()
- try assignSingletonsToScopes(typeDescriptionToScopeMap: typeDescriptionToScopeMap)
  try propagateUndeclaredInheritedProperties(typeDescriptionToScopeMap: typeDescriptionToScopeMap)
  let rootScopes = rootInstantiableTypes.compactMap({ typeDescriptionToScopeMap[$0] })
  _ = rootScopes
@@ -69,7 +67,6 @@ public final class DependencyTreeGenerator {
 
  /// A collection of `@Instantiable`-decorated types that do not explicitly inherit dependencies.
  /// - Note: These are not necessarily roots in the build graph, since these types may be instantiated by another `@Instantiable`.
- /// These types may also inherit (rather than construct) a `@Singleton` dependency.
  private lazy var possibleRootInstantiableTypes: Set<TypeDescription> = Set(
  typeDescriptionToFulfillingInstantiableMap
  .values
@@ -180,69 +177,9 @@ public final class DependencyTreeGenerator {
  }
  scope.propertiesToInstantiate.append(contentsOf: additionalPropertiesToInstantiate)
  }
- // Note: Singletons have not been assigned to scopes yet!
  return typeDescriptionToScopeMap
  }
 
- private func assignSingletonsToScopes(typeDescriptionToScopeMap: [TypeDescription: Scope]) throws {
- /// A mapping of singleton properties to the scopes that require this property.
- var singletonPropertyToScopesCountMap: [Property: Int] = typeDescriptionToScopeMap
- .values
- .reduce(into: [Property: Int]()) { partialResult, scope in
- for property in scope.instantiable.singletonProperties {
- partialResult[property, default: 0] += 1
- }
- }
- var scopeIdentifierToSingletonPropertyToScopesInTreeCount = [ObjectIdentifier: [Property: Int]]()
- func recordSingletonPropertiesOnScope(_ scope: Scope, parentScopes: [Scope]) {
- let scopes = [scope] + parentScopes // parentScopes has root scope as last.
- for singletonProperty in scope.instantiable.singletonProperties {
- for (index, scope) in scopes.enumerated() {
- let scopesInTreeUtilizingSingletonProperty = (scopeIdentifierToSingletonPropertyToScopesInTreeCount[ObjectIdentifier(scope)]?[singletonProperty] ?? 0) + 1
- defer {
- scopeIdentifierToSingletonPropertyToScopesInTreeCount[ObjectIdentifier(scope), default: [Property: Int]()][singletonProperty] = scopesInTreeUtilizingSingletonProperty
- }
- if
- singletonPropertyToScopesCountMap[singletonProperty] == scopesInTreeUtilizingSingletonProperty,
- let singletonPropertyScope = typeDescriptionToScopeMap[singletonProperty.typeDescription.asInstantiatedType]
- {
- scope.propertiesToInstantiate.append(Scope.PropertyToInstantiate(
- property: singletonProperty,
- instantiable: singletonPropertyScope.instantiable,
- scope: singletonPropertyScope,
- type: singletonProperty.nonLazyPropertyType // Singletons can not be lazy
- ))
- // Remove the singleton property from our tracker so we can find orphaned singletons later.
- singletonPropertyToScopesCountMap[singletonProperty] = nil
- // Visit the scope we just placed.
- recordSingletonPropertiesOnScope(singletonPropertyScope, parentScopes: Array(scopes.dropFirst(index)))
- // We don't need to keep traversing up the tree because we found what we're looking for.
- break
- }
- }
- }
- for childScope in scope.propertiesToInstantiate.map(\.scope) {
- guard !parentScopes.contains(where: { $0 === childScope }) else {
- // We've previously visited this child scope.
- // There is a cycle in our scope tree. Do not re-enter it.
- continue
- }
- recordSingletonPropertiesOnScope(childScope, parentScopes: scopes)
- }
- }
-
- let rootScopes = rootInstantiableTypes.compactMap({ typeDescriptionToScopeMap[$0] })
- for rootScope in rootScopes {
- recordSingletonPropertiesOnScope(rootScope, parentScopes: [])
- }
- if !singletonPropertyToScopesCountMap.isEmpty {
- throw DependencyTreeGeneratorError.unsatisfiableSingletons(
- Array(singletonPropertyToScopesCountMap.keys),
- roots: rootScopes.map(\.instantiable.concreteInstantiableType)
- )
- }
- }
-
  private func propagateUndeclaredInheritedProperties(typeDescriptionToScopeMap: [TypeDescription: Scope]) throws {
  var unfulfillableProperties = [DependencyTreeGeneratorError.UnfulfillableProperty]()
  func propagateUndeclaredInheritedProperties(on scope: Scope, parentScopes: [Scope]) {
@@ -320,7 +257,7 @@ public final class DependencyTreeGenerator {
 extension Dependency {
  fileprivate var isInstantiated: Bool {
  switch source {
- case .instantiated, .lazyInstantiated, .singleton:
+ case .instantiated, .lazyInstantiated:
  return true
  case .forwarded, .inherited:
  return false

Sources/SafeDICore/Models/Dependency.swift

@@ -21,7 +21,7 @@
 import SwiftSyntax
 
 /// A representation of a dependency.
-/// e.g. `@Singleton let mySingleton: MySingleton`
+/// e.g. `@Instantiated let myService: MyService`
 public struct Dependency: Codable, Hashable {
 
  // MARK: Public
@@ -31,7 +31,7 @@ public struct Dependency: Codable, Hashable {
 
  public var isForwarded: Bool {
  switch source {
- case .instantiated, .lazyInstantiated, .inherited, .singleton:
+ case .instantiated, .lazyInstantiated, .inherited:
  return false
  case .forwarded:
  return true
@@ -42,7 +42,6 @@ public struct Dependency: Codable, Hashable {
  case instantiated = "Instantiated"
  case lazyInstantiated = "LazyInstantiated"
  case inherited = "Inherited"
- case singleton = "Singleton"
  case forwarded = "Forwarded"
 
  public var description: String {
@@ -62,7 +61,7 @@ public struct Dependency: Codable, Hashable {
  /// The label by which this property is referenced in an initializer.
  var initializerArgumentLabel: String {
  switch source {
- case .instantiated, .inherited, .singleton, .forwarded:
+ case .instantiated, .inherited, .forwarded:
  return property.label
  case .lazyInstantiated:
  return "\(property.label)\(Self.instantiatorType)"
@@ -72,7 +71,7 @@ public struct Dependency: Codable, Hashable {
  /// The type description by which this property is referenced in an initializer.
  var initializerArgumentTypeDescription: TypeDescription {
  switch source {
- case .instantiated, .inherited, .singleton, .forwarded:
+ case .instantiated, .inherited, .forwarded:
  return property.typeDescription
  case .lazyInstantiated:
  // TODO: fully qualify this type with `SafeDI.` member prefix

Sources/SafeDICore/Models/Initializer.swift

@@ -199,7 +199,6 @@ public struct Initializer: Codable, Equatable {
  switch dependency.source {
  case .instantiated,
  .inherited,
- .singleton,
  .forwarded:
  CodeBlockItemSyntax(
  item: .expr(ExprSyntax(InfixOperatorExprSyntax(

Sources/SafeDICore/Models/Instantiable.swift

@@ -54,11 +54,6 @@ public struct Instantiable: Codable, Hashable {
  .filter { $0.source == .lazyInstantiated }
  .map(\.property)
  }
- var singletonProperties: [Property] {
- dependencies
- .filter { $0.source == .singleton }
- .map(\.property)
- }
  var forwardedProperties: [Property] {
  dependencies
  .filter { $0.source == .forwarded }

Sources/SafeDICore/Models/Scope.swift

@@ -73,9 +73,9 @@ final class Scope {
  }
  }
 
- var instantiatedProperties = Set<Property>()
- var lazyInstantiatedProperties = Set<Property>()
- lazy var inheritedProperties = calculateInheritedProperties()
+ private(set) var instantiatedProperties = Set<Property>()
+ private(set) var lazyInstantiatedProperties = Set<Property>()
+ private(set) lazy var inheritedProperties = calculateInheritedProperties()
 
  var allInheritedProperties: Set<Property> {
  inheritedProperties.union(undeclaredInheritedProperties)
@@ -93,13 +93,11 @@ final class Scope {
  .instantiated,
  .lazyInstantiated:
  return false
- case .inherited,
- // We will subtract out singletons created on this scope next.
- .singleton:
+ case .inherited:
  return true
  }
  }
  .map(\.property)
- ).subtracting(Set(propertiesToInstantiate.map(\.property)))
+ )
  }
 }

Tests/SafeDICoreTests/InitializerTests.swift

@@ -544,7 +544,7 @@ final class InitializerTests: XCTestCase {
  label: "invariantC",
  typeDescription: .simple(name: "InvariantC")
  ),
- source: .singleton
+ source: .instantiated
  )
  ],
  typeIsClass: false,

Tests/SafeDIMacrosTests/InjectableMacroTests.swift

@@ -34,7 +34,6 @@ final class InjectableMacroTests: XCTestCase {
  let testMacros: [String: Macro.Type] = [
  Dependency.Source.instantiated.rawValue: InjectableMacro.self,
  Dependency.Source.inherited.rawValue: InjectableMacro.self,
- Dependency.Source.singleton.rawValue: InjectableMacro.self,
  Dependency.Source.forwarded.rawValue: InjectableMacro.self,
  ]
 

Tests/SafeDIMacrosTests/InstantiableMacroTests.swift

@@ -33,7 +33,6 @@ final class InstantiableMacroTests: XCTestCase {
  InstantiableVisitor.macroName: InstantiableMacro.self,
  Dependency.Source.instantiated.rawValue: InjectableMacro.self,
  Dependency.Source.inherited.rawValue: InjectableMacro.self,
- Dependency.Source.singleton.rawValue: InjectableMacro.self,
  Dependency.Source.forwarded.rawValue: InjectableMacro.self,
  ]
 
@@ -175,7 +174,7 @@ final class InstantiableMacroTests: XCTestCase {
  public let invariantA: InvariantA
  @Inherited
  let invariantB: InvariantB
- @Singleton
+ @Instantiated
  private let invariantC: InvariantC
  }
  """,
@@ -292,7 +291,7 @@ final class InstantiableMacroTests: XCTestCase {
  private let invariantA: invariantA
  @Inherited
  private let invariantB: InvariantB
- @Singleton
+ @Instantiated
  private let invariantC: InvariantC
  }
  """,
@@ -417,7 +416,7 @@ final class InstantiableMacroTests: XCTestCase {
  let variantB: VariantB
  @Instantiated
  private let invariantA: InvariantA
- @Singleton
+ @Instantiated
  public let invariantB: InvariantB
  }
  """,
@@ -487,7 +486,7 @@ final class InstantiableMacroTests: XCTestCase {
  }
 
  @Inherited
- ╰─ 🛑 Dependency can have at most one of @Instantiated, @Inherited, @Singleton, or @Forwarded attached macro
+ ╰─ 🛑 Dependency can have at most one of @Instantiated, @Inherited, or @Forwarded attached macro
  ✏️ Remove excessive attached macros
  @Instantiated
  let invariantA: InvariantA