BridgeJS: Enforce throws(JSException) for @js protocol properties

Author: krodak

Plugins/BridgeJS/Sources/BridgeJSCore/ClosureCodegen.swift

@@ -61,6 +61,11 @@ public struct ClosureCodegen {
 
         // Generate the call and return value lifting
         try builder.call(returnType: signature.returnType)
+
+        if signature.isThrows {
+            builder.body.append("if let error = _swift_js_take_exception() { throw error }")
+        }
+
         try builder.liftReturnValue(returnType: signature.returnType)
 
         // Get the body code

Plugins/BridgeJS/Sources/BridgeJSCore/ExportSwift.swift

@@ -1447,7 +1447,7 @@ struct ProtocolCodegen {
         let getterBuilder = ImportTS.CallJSEmission(
             moduleName: moduleName,
             abiName: getterAbiName,
-            context: .exportSwift
+            context: property.effects.isThrows ? .exportSwiftProtocol : .exportSwift
         )
         try getterBuilder.lowerParameter(param: Parameter(label: nil, name: "jsObject", type: .jsObject(nil)))
         try getterBuilder.call(returnType: property.type)
@@ -1466,6 +1466,12 @@ struct ProtocolCodegen {
         )
 
         if property.isReadonly {
+            // Build effect specifiers for getter if property throws
+            let getterEffects =
+                property.effects.isThrows || property.effects.isAsync
+                ? ImportTS.buildAccessorEffect(throws: property.effects.isThrows, async: property.effects.isAsync)
+                : nil
+
             let propertyDecl = VariableDeclSyntax(
                 bindingSpecifier: .keyword(.var),
                 bindings: PatternBindingListSyntax {
@@ -1479,6 +1485,7 @@ struct ProtocolCodegen {
                                 AccessorDeclListSyntax {
                                     AccessorDeclSyntax(
                                         accessorSpecifier: .keyword(.get),
+                                        effectSpecifiers: getterEffects,
                                         body: getterBuilder.getBody()
                                     )
                                 }

Plugins/BridgeJS/Sources/BridgeJSCore/SwiftToSkeleton.swift

@@ -1057,6 +1057,29 @@ private final class ExportSwiftAPICollector: SyntaxAnyVisitor {
         return Effects(isAsync: isAsync, isThrows: isThrows, isStatic: isStatic)
     }
 
+    private func collectEffectsFromAccessor(_ accessor: AccessorDeclSyntax) -> Effects? {
+        let isAsync = accessor.effectSpecifiers?.asyncSpecifier != nil
+        var isThrows = false
+        if let throwsClause = accessor.effectSpecifiers?.throwsClause {
+            guard let thrownType = throwsClause.type else {
+                diagnose(
+                    node: throwsClause,
+                    message: "Thrown type is not specified, only JSException is supported for now"
+                )
+                return nil
+            }
+            guard thrownType.trimmedDescription == "JSException" else {
+                diagnose(
+                    node: throwsClause,
+                    message: "Only JSException is supported for thrown type, got \(thrownType.trimmedDescription)"
+                )
+                return nil
+            }
+            isThrows = true
+        }
+        return Effects(isAsync: isAsync, isThrows: isThrows, isStatic: false)
+    }
+
     private func extractNamespace(
         from jsAttribute: AttributeSyntax
     ) -> [String]? {
@@ -1654,18 +1677,62 @@ private final class ExportSwiftAPICollector: SyntaxAnyVisitor {
             guard let accessorBlock = binding.accessorBlock else {
                 diagnose(
                     node: binding,
-                    message: "Protocol property must specify { get } or { get set }",
-                    hint: "Add { get } for readonly or { get set } for readwrite property"
+                    message: "Protocol property must specify { get throws(JSException) }",
+                    hint: "Add { get throws(JSException) } for the property accessor"
                 )
                 continue
             }
 
-            let isReadonly = hasOnlyGetter(accessorBlock)
+            // Find the getter accessor
+            let getterAccessor: AccessorDeclSyntax?
+            switch accessorBlock.accessors {
+            case .accessors(let accessors):
+                getterAccessor = accessors.first { $0.accessorSpecifier.tokenKind == .keyword(.get) }
+            case .getter:
+                diagnose(
+                    node: accessorBlock,
+                    message: "@JS protocol property getter must declare throws(JSException)",
+                    hint: "Use { get throws(JSException) } syntax"
+                )
+                continue
+            }
+
+            guard let getter = getterAccessor else {
+                diagnose(node: accessorBlock, message: "Protocol property must have a getter")
+                continue
+            }
+
+            // Check for setter - not allowed with throwing getter
+            if case .accessors(let accessors) = accessorBlock.accessors {
+                if accessors.contains(where: { $0.accessorSpecifier.tokenKind == .keyword(.set) }) {
+                    diagnose(
+                        node: accessorBlock,
+                        message: "@JS protocol cannot have { get set } properties",
+                        hint:
+                            "Use readonly property with setter method: var \(propertyName): \(typeAnnotation.type.trimmedDescription) { get throws(JSException) } and func set\(propertyName.capitalized)(_ value: \(typeAnnotation.type.trimmedDescription)) throws(JSException)"
+                    )
+                    continue
+                }
+            }
+
+            guard let effects = collectEffectsFromAccessor(getter) else {
+                continue
+            }
+
+            guard effects.isThrows else {
+                diagnose(
+                    node: getter,
+                    message: "@JS protocol property getter must be throws",
+                    hint: "Declare the getter as 'get throws(JSException)'"
+                )
+                continue
+            }
 
             let exportedProperty = ExportedProtocolProperty(
                 name: propertyName,
                 type: propertyType,
-                isReadonly: isReadonly
+                isReadonly: true,  // Always readonly since { get set } with throws is not allowed
+                effects: effects
             )
 
             if var currentProtocol = exportedProtocolByName[protocolKey] {

Plugins/BridgeJS/Sources/BridgeJSLink/BridgeJSLink.swift

@@ -3281,14 +3281,40 @@ extension BridgeJSLink {
         for param in method.parameters {
             try thunkBuilder.liftParameter(param: param)
         }
-        let returnExpr = try thunkBuilder.callMethod(name: method.name, returnType: method.returnType)
+
+        // Check if this is a setter method (setFoo pattern with single parameter and void return)
+        // If so, convert to property assignment for JavaScript compatibility
+        let returnExpr: String?
+        if let propertyName = extractSetterPropertyName(from: method.name),
+            method.parameters.count == 1,
+            method.returnType == .void
+        {
+            thunkBuilder.callPropertySetter(name: propertyName, returnType: method.returnType)
+            returnExpr = nil
+        } else {
+            returnExpr = try thunkBuilder.callMethod(name: method.name, returnType: method.returnType)
+        }
+
         let funcLines = thunkBuilder.renderFunction(
             name: method.abiName,
             returnExpr: returnExpr,
             returnType: method.returnType
         )
         importObjectBuilder.assignToImportObject(name: method.abiName, function: funcLines)
     }
+
+    /// Extracts property name from a setter method name (e.g., "setFoo" -> "foo")
+    /// Returns nil if the method name doesn't match the setter pattern
+    private func extractSetterPropertyName(from methodName: String) -> String? {
+        guard methodName.hasPrefix("set"), methodName.count > 3 else {
+            return nil
+        }
+        let propertyName = String(methodName.dropFirst(3))
+        guard !propertyName.isEmpty else {
+            return nil
+        }
+        return propertyName.prefix(1).lowercased() + propertyName.dropFirst()
+    }
 }
 
 /// Utility enum for generating default value representations in JavaScript/TypeScript

Plugins/BridgeJS/Sources/BridgeJSSkeleton/BridgeJSSkeleton.swift

@@ -406,15 +406,18 @@ public struct ExportedProtocolProperty: Codable, Equatable, Sendable {
     public let name: String
     public let type: BridgeType
     public let isReadonly: Bool
+    public let effects: Effects
 
     public init(
         name: String,
         type: BridgeType,
-        isReadonly: Bool
+        isReadonly: Bool,
+        effects: Effects
     ) {
         self.name = name
         self.type = type
         self.isReadonly = isReadonly
+        self.effects = effects
     }
 }
 

Plugins/BridgeJS/Tests/BridgeJSToolTests/Inputs/MacroSwift/Protocol.swift

@@ -36,17 +36,27 @@ import JavaScriptKit
 }
 
 @JS protocol MyViewControllerDelegate {
-    var eventCount: Int { get set }
-    var delegateName: String { get }
-    var optionalName: String? { get set }
-    var optionalRawEnum: ExampleEnum? { get set }
-    var rawStringEnum: ExampleEnum { get set }
-    var result: Result { get set }
-    var optionalResult: Result? { get set }
-    var direction: Direction { get set }
-    var directionOptional: Direction? { get set }
-    var priority: Priority { get set }
-    var priorityOptional: Priority? { get set }
+    var eventCount: Int { get throws(JSException) }
+    var delegateName: String { get throws(JSException) }
+    var optionalName: String? { get throws(JSException) }
+    var optionalRawEnum: ExampleEnum? { get throws(JSException) }
+    var rawStringEnum: ExampleEnum { get throws(JSException) }
+    var result: Result { get throws(JSException) }
+    var optionalResult: Result? { get throws(JSException) }
+    var direction: Direction { get throws(JSException) }
+    var directionOptional: Direction? { get throws(JSException) }
+    var priority: Priority { get throws(JSException) }
+    var priorityOptional: Priority? { get throws(JSException) }
+    func setEventCount(_ value: Int) throws(JSException)
+    func setOptionalName(_ value: String?) throws(JSException)
+    func setOptionalRawEnum(_ value: ExampleEnum?) throws(JSException)
+    func setRawStringEnum(_ value: ExampleEnum) throws(JSException)
+    func setResult(_ value: Result) throws(JSException)
+    func setOptionalResult(_ value: Result?) throws(JSException)
+    func setDirection(_ value: Direction) throws(JSException)
+    func setDirectionOptional(_ value: Direction?) throws(JSException)
+    func setPriority(_ value: Priority) throws(JSException)
+    func setPriorityOptional(_ value: Priority?) throws(JSException)
     func onSomethingHappened() throws(JSException)
     func onValueChanged(_ value: String) throws(JSException)
     func onCountUpdated(count: Int) throws(JSException) -> Bool