Bind @SharedObject members directly into the JS object via _decorateSharedObject (#22)

Author: tsapeta

apple/Sources/ExpoModulesMacros/DecorateModuleBuilder.swift

@@ -244,55 +244,3 @@ private func hasAppContextInitializer(_ classDecl: ClassDeclSyntax) -> Bool {
   }
   return false
 }
-
-// MARK: - Member builders
-
-private func collectProperties(
-  varDecl: VariableDeclSyntax,
-  attribute: AttributeSyntax
-) -> [JSProperty] {
-  let jsNameOverride = jsNameArgument(of: attribute)
-  // A `let` is never settable; only `var` bindings can carry a setter.
-  let isVar = varDecl.bindingSpecifier.tokenKind == .keyword(.var)
-
-  return varDecl.bindings.compactMap { binding in
-    guard let ident = binding.pattern.as(IdentifierPatternSyntax.self) else {
-      return nil
-    }
-    let swiftName = ident.identifier.text
-    // Prefer the explicit annotation; recover the type from a literal default (`var x = false`)
-    // when there's none. `nil` falls back to inference at the use site.
-    let valueType = binding.typeAnnotation?.type.trimmedDescription
-      ?? binding.initializer.flatMap { inferredLiteralType(of: $0.value) }
-    return JSProperty(
-      swiftName: swiftName,
-      jsName: jsNameOverride ?? swiftName,
-      valueType: valueType,
-      isSettable: isVar && bindingIsSettable(binding)
-    )
-  }
-}
-
-/// Whether a `var` binding is settable from JS. A stored property (no accessor block) is settable;
-/// a computed property is settable only when it declares an explicit `set` accessor. A getter-only
-/// computed property (`{ get }` or a single getter body) stays read-only. `willSet`/`didSet`
-/// observers imply stored storage, which is also settable.
-private func bindingIsSettable(_ binding: PatternBindingSyntax) -> Bool {
-  guard let accessorBlock = binding.accessorBlock else {
-    return true
-  }
-  switch accessorBlock.accessors {
-  case .accessors(let accessors):
-    return accessors.contains { accessor in
-      switch accessor.accessorSpecifier.tokenKind {
-      case .keyword(.set), .keyword(.willSet), .keyword(.didSet):
-        return true
-      default:
-        return false
-      }
-    }
-  case .getter:
-    return false
-  }
-}
-

apple/Sources/ExpoModulesMacros/ExpoModuleMacro.swift

@@ -0,0 +1,60 @@
+import SwiftSyntax
+
+/// A `@JS init` collected for direct JSI binding. A shared-object type has at most one (JS classes
+/// have a single constructor). Instead of a `Constructor { … }` DSL entry, the macro synthesizes a
+/// static `_constructSharedObject(...)` that decodes the JS arguments and returns a fresh instance;
+/// unlike the method/property bindings it produces the native instance rather than recovering one.
+internal struct JSConstructor {
+  let parameters: [FunctionParameterSyntax]
+
+  init(initDecl: InitializerDeclSyntax) {
+    self.parameters = Array(initDecl.signature.parameterClause.parameters)
+  }
+
+  /// The body statements, indented with `indent`: arity guard, per-argument decode (primitives via a
+  /// typed accessor, others via the dynamic converter), then `return <Type>(label: arg0, …)`.
+  private func bodyStatements(typeName: String, indent: String) -> String {
+    var lines: [String] = []
+
+    lines.append(
+      """
+      guard arguments.count == \(parameters.count) else {
+        throw Exceptions.ArgumentsRangeMismatch((functionName: "\(typeName)", received: arguments.count, required: \(parameters.count), maximum: \(parameters.count)))
+      }
+      """)
+
+    var callArguments: [String] = []
+    for (index, parameter) in parameters.enumerated() {
+      let type = parameter.type.trimmedDescription
+
+      if let accessor = fastDecodeAccessor(for: type) {
+        lines.append("let arg\(index) = try arguments.unownedValue(at: \(index)).\(accessor)()")
+      } else {
+        let exprType = expressionType(type)
+        lines.append(
+          "let arg\(index) = try \(exprType).getDynamicType().cast(jsValue: arguments[\(index)], appContext: appContext) as! \(exprType)")
+      }
+
+      let label = parameter.firstName.text
+      callArguments.append(label == "_" ? "arg\(index)" : "\(label): arg\(index)")
+    }
+
+    lines.append("return \(typeName)(\(callArguments.joined(separator: ", ")))")
+
+    return lines
+      .flatMap { $0.split(separator: "\n", omittingEmptySubsequences: false) }
+      .map { indent + $0 }
+      .joined(separator: "\n")
+  }
+
+  /// The static `_constructSharedObject` entry point the runtime calls to build an instance from JS
+  /// arguments, returning the concrete type. `this`/`appContext` may go unreferenced, which is harmless.
+  func buildConstructor(typeName: String) -> DeclSyntax {
+    return """
+      @JavaScriptActor
+      public static func _constructSharedObject(this: JavaScriptValue, arguments: borrowing JavaScriptValuesBuffer, in runtime: JavaScriptRuntime, appContext: AppContext) throws -> \(raw: typeName) {
+      \(raw: bodyStatements(typeName: typeName, indent: "  "))
+      }
+      """
+  }
+}

apple/Sources/ExpoModulesMacros/JSConstructor.swift

@@ -256,3 +256,76 @@ internal func expressionType(_ type: String) -> String {
   }
   return type.dropLast() + "?"
 }
+
+// MARK: - @JS property collection
+
+/// Collects the `@JS var` bindings of a declaration into `JSProperty` values for direct JSI binding.
+/// Shared between `@ExpoModule` and `@SharedObject` — the resulting properties are receiver-agnostic;
+/// the decorator that emits them picks the receiver (module `self` vs. shared-object `_self`).
+internal func collectProperties(
+  varDecl: VariableDeclSyntax,
+  attribute: AttributeSyntax
+) -> [JSProperty] {
+  let jsNameOverride = jsNameArgument(of: attribute)
+  // A `let` is never settable; only `var` bindings can carry a setter.
+  let isVar = varDecl.bindingSpecifier.tokenKind == .keyword(.var)
+
+  return varDecl.bindings.compactMap { binding in
+    guard let ident = binding.pattern.as(IdentifierPatternSyntax.self) else {
+      return nil
+    }
+    let swiftName = ident.identifier.text
+    // Prefer the explicit annotation; recover the type from a literal default (`var x = false`)
+    // when there's none. `nil` falls back to inference at the use site.
+    let valueType = binding.typeAnnotation?.type.trimmedDescription
+      ?? binding.initializer.flatMap { inferredLiteralType(of: $0.value) }
+    return JSProperty(
+      swiftName: swiftName,
+      jsName: jsNameOverride ?? swiftName,
+      valueType: valueType,
+      isSettable: isVar && bindingIsSettable(binding)
+    )
+  }
+}
+
+/// Whether a `var` binding is settable from JS. A stored property (no accessor block) is settable;
+/// a computed property is settable only when it declares an explicit `set` accessor. A getter-only
+/// computed property (`{ get }` or a single getter body) stays read-only. `willSet`/`didSet`
+/// observers imply stored storage, which is also settable.
+private func bindingIsSettable(_ binding: PatternBindingSyntax) -> Bool {
+  guard let accessorBlock = binding.accessorBlock else {
+    return true
+  }
+  switch accessorBlock.accessors {
+  case .accessors(let accessors):
+    return accessors.contains { accessor in
+      switch accessor.accessorSpecifier.tokenKind {
+      case .keyword(.set), .keyword(.willSet), .keyword(.didSet):
+        return true
+      default:
+        return false
+      }
+    }
+  case .getter:
+    return false
+  }
+}
+
+/// The throwing `JavaScriptUnownedValue` accessor that decodes the given primitive type directly
+/// (`asDouble()` for `Double`, etc.), bypassing the dynamic-type converter. Returns `nil` for types
+/// without a dedicated accessor (arrays, records, optionals, shared objects, other numeric widths),
+/// which decode through `getDynamicType().cast(...)`.
+func fastDecodeAccessor(for type: String) -> String? {
+  switch type {
+  case "Bool":
+    return "asBool"
+  case "Int":
+    return "asInt"
+  case "Double":
+    return "asDouble"
+  case "String":
+    return "asString"
+  default:
+    return nil
+  }
+}

apple/Sources/ExpoModulesMacros/MacroHelpers.swift

@@ -0,0 +1,58 @@
+import SwiftSyntax
+
+/// Where a directly-bound closure gets the Swift value it calls into. A module is a singleton, so its
+/// bindings call `self` and ignore the JS `this`; a shared object has a distinct native instance per JS
+/// object, so its bindings recover the typed receiver from `this`.
+internal enum Receiver {
+  /// The module singleton; the closure captures `self` strong.
+  case module
+  /// A shared object of the given concrete type; the closure captures nothing and recovers the receiver
+  /// from `this` per call.
+  case sharedObject(typeName: String)
+
+  /// The expression the body calls members on: `self` for a module, `_self` (bound by `unwrapStatement`)
+  /// for a shared object. The leading underscore avoids colliding with a user member like `var owner`.
+  var callee: String {
+    switch self {
+    case .module:
+      return "self"
+    case .sharedObject:
+      return "_self"
+    }
+  }
+
+  /// The JS object the decorator binds members onto, matching its first parameter: `object` for a
+  /// module (its own JS object), `prototype` for a shared object (the shared class prototype).
+  var decoratedObject: String {
+    switch self {
+    case .module:
+      return "object"
+    case .sharedObject:
+      return "prototype"
+    }
+  }
+
+  /// The leading body line binding the receiver, or `nil` for a module (it reads `self` directly). For a
+  /// shared object, `native(from:as:)` recovers the typed instance from the borrowed `this`, throwing on
+  /// a foreign object or a type mismatch.
+  var unwrapStatement: String? {
+    switch self {
+    case .module:
+      return nil
+    case .sharedObject(let typeName):
+      return "let _self = try SharedObject.native(from: this.asObject(in: runtime), as: \(typeName).self)"
+    }
+  }
+
+  /// The capture-clause fragment (with a trailing space, or empty when nothing is captured). A module
+  /// captures `self` strong; a shared object captures nothing of the instance. `appContext`, when used,
+  /// is captured weak in both cases.
+  func captureClause(usesAppContext: Bool) -> String {
+    switch self {
+    case .module:
+      return usesAppContext ? "[weak appContext, self] " : "[self] "
+    case .sharedObject:
+      return usesAppContext ? "[weak appContext] " : ""
+    }
+  }
+}