feat: added actor support

Author: soumyamahunt

Sources/CodableMacroPlugin/Attributes/Codable/Codable+Expansion.swift

@@ -70,10 +70,16 @@ extension Codable: MemberMacro, ExtensionMacro {
         in context: some MacroExpansionContext
     ) throws -> [DeclSyntax] {
         guard
-            let exp = AttributeExpander(for: declaration, in: context),
-            let decl = declaration.as(ClassDeclSyntax.self),
-            case let type = IdentifierTypeSyntax(name: decl.name)
+            let exp = AttributeExpander(for: declaration, in: context)
         else { return [] }
+        let type: IdentifierTypeSyntax
+        if let decl = declaration.as(ClassDeclSyntax.self) {
+            type = .init(name: decl.name)
+        } else if let decl = declaration.as(ActorDeclSyntax.self) {
+            type = .init(name: decl.name)
+        } else {
+            return []
+        }
         let exts = exp.codableExpansion(for: type, to: protocols, in: context)
         return exts.flatMap { `extension` in
             `extension`.memberBlock.members.map { DeclSyntax($0.decl) }
@@ -120,7 +126,9 @@ extension Codable: MemberMacro, ExtensionMacro {
             let exp = AttributeExpander(for: declaration, in: context)
         else { return [] }
         var exts = exp.codableExpansion(for: type, to: protocols, in: context)
-        if declaration.is(ClassDeclSyntax.self) {
+        if declaration.is(ClassDeclSyntax.self)
+            || declaration.is(ActorDeclSyntax.self)
+        {
             for (index, var `extension`) in exts.enumerated() {
                 `extension`.memberBlock = .init(members: [])
                 exts[index] = `extension`

Sources/CodableMacroPlugin/Attributes/Codable/Codable.swift

@@ -48,7 +48,7 @@ struct Codable: Attribute {
         return AggregatedDiagnosticProducer {
             expect(
                 syntaxes: StructDeclSyntax.self, ClassDeclSyntax.self,
-                EnumDeclSyntax.self
+                EnumDeclSyntax.self, ActorDeclSyntax.self
             )
             cantDuplicate()
         }

Sources/CodableMacroPlugin/Attributes/MemberInit/MemberInit.swift

@@ -39,7 +39,7 @@ struct MemberInit: Attribute {
     /// - Returns: The built diagnoser instance.
     func diagnoser() -> DiagnosticProducer {
         return AggregatedDiagnosticProducer {
-            expect(syntaxes: StructDeclSyntax.self)
+            expect(syntaxes: StructDeclSyntax.self, ActorDeclSyntax.self)
             cantDuplicate()
         }
     }

Sources/CodableMacroPlugin/Variables/ComposedVariable.swift

@@ -137,3 +137,21 @@ where Self: EnumCaseVariable, Wrapped: EnumCaseVariable {
     /// Provides associated variables of the underlying variable value.
     var variables: [any AssociatedVariable] { base.variables }
 }
+
+extension ComposedVariable where Self: TypeVariable, Wrapped: TypeVariable {
+    /// Provides the syntax for `CodingKeys` declarations.
+    ///
+    /// Provides members generated by the underlying variable value.
+    ///
+    /// - Parameters:
+    ///   - protocols: The protocols for which conformance generated.
+    ///   - context: The context in which to perform the macro expansion.
+    ///
+    /// - Returns: The `CodingKeys` declarations.
+    func codingKeys(
+        confirmingTo protocols: [TypeSyntax],
+        in context: some MacroExpansionContext
+    ) -> MemberBlockItemListSyntax {
+        return base.codingKeys(confirmingTo: protocols, in: context)
+    }
+}

Sources/CodableMacroPlugin/Variables/Syntax/MemberGroupSyntax.swift

@@ -92,6 +92,13 @@ extension ClassDeclSyntax: MemberGroupSyntax, VariableSyntax {
     typealias Variable = ClassVariable
 }
 
+extension ActorDeclSyntax: MemberGroupSyntax, VariableSyntax {
+    /// The `Variable` type this syntax represents.
+    ///
+    /// The actor variable type used with current declaration.
+    typealias Variable = ActorVariable
+}
+
 extension EnumDeclSyntax: MemberGroupSyntax, VariableSyntax {
     /// The `Variable` type this syntax represents.
     ///

Sources/CodableMacroPlugin/Variables/Type/ActorVariable.swift

@@ -0,0 +1,53 @@
+@_implementationOnly import SwiftSyntax
+@_implementationOnly import SwiftSyntaxMacros
+
+/// A `TypeVariable` that provides `Codable` conformance
+/// for an `actor` type.
+///
+/// This type can be used for `actor`s for `Decodable` conformance and
+/// `Encodable` implementation without conformance.
+struct ActorVariable: TypeVariable, DeclaredVariable, ComposedVariable,
+    InitializableVariable
+{
+    /// The initialization type of this variable.
+    ///
+    /// Initialization type is the same as underlying member group variable.
+    typealias Initialization = MemberGroup<ActorDeclSyntax>.Initialization
+    /// The member group used to generate conformance implementations.
+    let base: MemberGroup<ActorDeclSyntax>
+
+    /// Creates a new variable from declaration and expansion context.
+    ///
+    /// Uses the actor declaration with member group to generate conformances.
+    ///
+    /// - Parameters:
+    ///   - decl: The declaration to read from.
+    ///   - context: The context in which the macro expansion performed.
+    init(from decl: ActorDeclSyntax, in context: some MacroExpansionContext) {
+        self.base = .init(from: decl, in: context)
+    }
+
+    /// Provides the syntax for encoding at the provided location.
+    ///
+    /// Uses member group to generate syntax, the implementation is added
+    /// while not conforming to `Encodable` protocol.
+    ///
+    /// - Parameters:
+    ///   - context: The context in which to perform the macro expansion.
+    ///   - location: The encoding location.
+    ///
+    /// - Returns: The generated encoding syntax.
+    func encoding(
+        in context: some MacroExpansionContext,
+        to location: TypeCodingLocation
+    ) -> TypeGenerated? {
+        guard
+            let generated = base.encoding(in: context, to: location)
+        else { return nil }
+        return .init(
+            code: generated.code, modifiers: generated.modifiers,
+            whereClause: generated.whereClause,
+            inheritanceClause: nil
+        )
+    }
+}

Sources/CodableMacroPlugin/Variables/Type/Data/ConstraintGenerator.swift

@@ -122,3 +122,4 @@ protocol GenericTypeDeclSyntax {
 extension StructDeclSyntax: GenericTypeDeclSyntax {}
 extension ClassDeclSyntax: GenericTypeDeclSyntax {}
 extension EnumDeclSyntax: GenericTypeDeclSyntax {}
+extension ActorDeclSyntax: GenericTypeDeclSyntax {}

Sources/MetaCodable/Codable/Codable.swift

@@ -1,5 +1,5 @@
-/// Generate `Codable` implementation of `struct`, `class`, `enum` types
-/// by leveraging custom attributes provided on variable declarations.
+/// Generate `Codable` implementation of `struct`, `class`, `enum`, `actor`
+/// types by leveraging custom attributes provided on variable declarations.
 ///
 /// # Usage
 /// By default the field name is used as `CodingKey` for the field value during
@@ -38,8 +38,8 @@
 ///   * If attached declaration already conforms to `Codable` this macro expansion
 ///     is skipped.
 ///
-/// - Important: The attached declaration must be of a `struct`, `class`
-///   or `enum` type. [See the limitations for this macro](<doc:Limitations>).
+/// - Important: The attached declaration must be of a `struct`, `class`, `enum`
+///   or `actor` type. [See the limitations for this macro](<doc:Limitations>).
 @attached(
     extension, conformances: Decodable, Encodable,
     names: named(CodingKeys), named(DecodingKeys),

Sources/MetaCodable/CodedAt.swift

@@ -76,13 +76,35 @@
 ///   }
 ///   ```
 ///
+/// * For enums, this attribute can be used along with ``TaggedAt(_:_:)``
+///   to support adjacently tagged enums. The path provided represents the path
+///   where associated values of each case is decoded/encoded.
+///   i.e. for JSON with following format:
+///   ```json
+///   {"t": "para", "c": [{...}, {...}]}
+///   ```
+///   ```json
+///   {"t": "str", "c": "the string"}
+///   ```
+///   enum representation can be created:
+///   ```swift
+///   @Codable
+///   @TaggedAt("t")
+///   @CodedAt("c")
+///   enum Block {
+///       case para([Inline]),
+///       case str(String),
+///   }
+///   ```
+///
 /// - Parameter path: The `CodingKey` path value located at.
 ///
 /// - Note: This macro on its own only validates if attached declaration
 ///   is a variable declaration. ``Codable()`` macro uses this macro
 ///   when generating final implementations.
 ///
-/// - Important: The field type must confirm to `Codable`.
+/// - Important: When applied to fields, the field type must confirm to
+///   `Codable`.
 @attached(peer)
 @available(swift 5.9)
 public macro CodedAt(_ path: StaticString...) =

Sources/MetaCodable/MetaCodable.docc/Limitations.md

@@ -31,3 +31,40 @@ struct Model {
 The ability to pass conformance data to macro for classes when performing member attribute expansion was introduced in [`Swift 5.9.2`](https://github.com/apple/swift-evolution/blob/main/proposals/0407-member-macro-conformances.md). Please make sure to upgrade to this version to have this working.
 
 Even with this it is unable for ``Codable()`` to get clear indication where conformance to `Codable` is implemented by current class or the super class. ``Codable()`` checks current class for the conformance implementation by checking implementation functions and the check will not work if some `typealias` used for `Decoder`/`Encoder` in implementation function definition.
+
+### Why enum-case associated values decoding/encoding are not customizable?
+
+The goal of ``MetaCodable`` is to allow same level of customization for enum-case associated values as it is allowed for `struct`/`class`/`actor` member properties. Unfortunately, as of now, `Swift` doesn't allow macro attributes (or any attributes) to be attached per enum-case arguments.
+
+[A pitch has been created to allow this support in `Swift`](https://forums.swift.org/t/attached-macro-support-for-enum-case-arguments/67952), you can support this pitch on `Swift` forum if this feature will benefit you.
+
+The current workaround is to extract enum-case arguments to separate `struct` and have the customization options in the `struct` itself. i.e. since following isn't possible:
+
+```swift
+@Codable
+enum SomeEnum {
+    case string(@CodedAt("data") String)
+}
+```
+
+you can convert it to:
+
+```swift
+@Codable
+enum SomeEnum {
+    case string(StringData)
+
+    @Codable
+    struct StringData {
+        let data: String
+    }
+}
+```
+
+### Why `actor` conformance to `Encodable` not generated?
+
+For `actor`s ``Codable()`` generates `Decodable` conformance, while `Encodable` conformance isn't generated, only `encode(to:)` method implementation is generated which is isolated to `actor`.
+
+To generate `Encodable` conformance, the `encode(to:)` method must be `nonisolated` to `actor`, and since `encode(to:)` method must be synchronous making it `nonisolated` will prevent accessing mutable properties.
+
+Due to these limitations, `Encodable` conformance isn't generated, users has to implement the conformance manually.