feat(minor): [sc-24016] enable isolation specification in generated equatable confomance (#29)

Author: supersonicbyte

Package.resolved

@@ -15,7 +15,7 @@ let package = Package(
         )
     ],
     dependencies: [
-        .package(url: "https://github.com/swiftlang/swift-syntax.git", "600.0.0"..<"602.0.0")
+        .package(url: "https://github.com/swiftlang/swift-syntax.git", "602.0.0" ..< "603.0.0")
     ],
     targets: [
         // Targets are the basic building blocks of a package, defining a module or a test suite.

Package.swift

@@ -76,6 +76,75 @@ extension ProfileView: Equatable {
         lhs.id == rhs.id && lhs.username == rhs.username
     }
 }
+```
+
+ ## Isolation
+`Equatable` macro supports generating the conformance with different isolation levels by using the `isolation` parameter.
+The parameter accepts three values: `.nonisolated` (default), `.isolated`, and `.main` (requires Swift 6.2 or later).
+The chosen isolation level will be applied to the generated conformances for both `Equatable` and `Hashable` (if applicable).
+
+### Nonisolated (default)
+The generated `Equatable` conformance is `nonisolated`, meaning it can be called from any context without isolation guarantees.
+```swift
+@Equatable(isolation: .nonisolated) (also omitting the parameter uses this mode)
+struct Person {
+    let name: String
+    let age: Int
+}
+```
+
+expands to:
+```swift
+extension Person: Equatable {
+nonisolated public static func == (lhs: Person, rhs: Person) -> Bool {
+    lhs.name == rhs.name && lhs.age == rhs.age
+}
+}
+```
+
+### Isolated
+The generated `Equatable` conformance is `isolated`, meaning it can only be called from within the actor's context.
+```swift
+@Equatable(isolation: .isolated)
+struct Person {
+    let name: String
+    let age: Int
+}
+```
+
+expands to:
+```swift
+extension Person: Equatable {
+public static func == (lhs: Person, rhs: Person) -> Bool {
+    lhs.name == rhs.name && lhs.age == rhs.age
+}
+}
+```
+
+### Main (requires Swift 6.2 or later)
+A common case is to have a `@MainActor` isolated type, SwiftUI views being a common example. Previously, the generated `Equatable` conformance had to be `nonisolated` in order to satisfy the protocol requirement.
+This would then restrict us to access only nonisolated properties of the type in the generated `Equatable` function — which meant that we had to ignore all `@MainActor` isolated properties in the equality comparison.
+Swift 6.2 introduced [isolated conformances](https://docs.swift.org/compiler/documentation/diagnostics/isolated-conformances/) allowing us to generate `Equatable` conformances
+which are bound to the `@MainActor`. In this way the generated `Equatable` conformance can access `@MainActor` isolated properties of the type synchronously and the compiler will guarantee that the conformance
+will be called only from the `@MainActor` context.
+
+We can do so by specifying `@Equatable(isolation: .main)`, e.g:
+```swift
+@Equatable(isolation: .main)
+@MainActor
+struct Person {
+    let name: String
+    let age: Int
+}
+```
+
+expands to:
+```swift
+extension Person: Equatable {
+    public static func == (lhs: Person, rhs: Person) -> Bool {
+        lhs.name == rhs.name && lhs.age == rhs.age
+    }
+}
 ```
 
 ## Safety Considerations
@@ -148,9 +217,8 @@ import Equatable
 @Equatable
 struct User: Hashable {
 
-let id: Int
-
-@EquatableIgnored var name = ""
+    let id: Int
+    @EquatableIgnored var name = ""
 }
 ```
 

README.md

@@ -67,8 +67,91 @@
 ///     }
 /// }
 /// ```
+///
+///
+/// ## Isolation
+/// `Equatable` macro supports generating the conformance with different isolation levels by using the `isolation` parameter.
+///  The parameter accepts three values: `.nonisolated` (default), `.isolated`, and `.main` (requires Swift 6.2 or later).
+///  The chosen isolation level will be applied to the generated conformances for both `Equatable` and `Hashable` (if applicable).
+///
+///  ### Nonisolated (default)
+///  The generated `Equatable` conformance is `nonisolated`, meaning it can be called from any context without isolation guarantees.
+///  ```swift
+///  @Equatable(isolation: .nonisolated) (also ommiting the parameter uses this mode)
+///    struct Person {
+///     let name: String
+///     let age: Int
+///   }
+///  ```
+///
+///  expands to:
+///  ```swift
+///  extension Person: Equatable {
+///   nonisolated public static func == (lhs: Person, rhs: Person) -> Bool {
+///     lhs.name == rhs.name && lhs.age == rhs.age
+///    }
+///  }
+///  ```
+///
+///  ### Isolated
+///  The generated `Equatable` conformance is `isolated`, meaning it can only be called from within the actor's context.
+///  ```swift
+///  @Equatable(isolation: .isolated)
+///  struct Person {
+///     let name: String
+///     let age: Int
+///  }
+///  ```
+///
+///  expands to:
+///  ```swift
+///  extension Person: Equatable {
+///   public static func == (lhs: Person, rhs: Person) -> Bool {
+///     lhs.name == rhs.name && lhs.age == rhs.age
+///    }
+///  }
+///  ```
+///
+///  ### Main (requires Swift 6.2 or later)
+///  A common case  is to have a `@MainActor` isolated type, SwiftUI views being a common example. Previously, the generated `Equatable` conformance had to be `nonisolated` in order to satisfy the protocol requirement.
+///  This would then restrict us to access only nonisolated properties of the type in the generated `Equatable` function — which ment that we had to ignore all `@MainActor` isolated properties in the equality comparison.
+///  Swift 6.2 introduced [isolated confomances](https://docs.swift.org/compiler/documentation/diagnostics/isolated-conformances/) allowing us to generate  `Equatable` confomances
+///  which are bound to the `@MainActor`. In this way the generated `Equatable` conformance can access `@MainActor` isolated properties of the type synchonously and the compiler will guarantee that the confomance
+///  will be called only from the `@MainActor` context.
+///
+///  We can do so by specifying `@Equatable(isolation: .main)`, e.g:
+///  ```swift
+///  @Equatable(isolation: .main)
+///  @MainActor
+///  struct Person {
+///     let name: String
+///     let age: Int
+///  }
+///  ```
+///
+///  expands to:
+///  ```swift
+///  extension Person: Equatable {
+///     public static func == (lhs: Person, rhs: Person) -> Bool {
+///         lhs.name == rhs.name && lhs.age == rhs.age
+///     }
+///  }
+///  ```
+///
 @attached(extension, conformances: Equatable, Hashable, names: named(==), named(hash(into:)))
-public macro Equatable() = #externalMacro(module: "EquatableMacros", type: "EquatableMacro")
+public macro Equatable(isolation: Isolation = .nonisolated) = #externalMacro(module: "EquatableMacros", type: "EquatableMacro")
+
+/// Isolation level for the generated Equatable functions.
+public enum Isolation {
+    /// The generated `Equatable` conformance is `nonisolated`.
+    case nonisolated
+    /// The generated `Equatable` conformance is`isolated`.
+    case isolated
+    #if swift(>=6.2)
+        /// The generated `Equatable` conformance is `@MainActor` isolated.
+        case main
+    #endif
+}
 
 /// A peer macro that marks properties to be ignored in `Equatable` conformance generation.
 ///