swiftwasm · kateinoigakukun · Feb 17, 2026 · Feb 17, 2026
diff --git a/Plugins/BridgeJS/Sources/BridgeJSMacros/JSClassMacro.swift b/Plugins/BridgeJS/Sources/BridgeJSMacros/JSClassMacro.swift
@@ -47,6 +47,21 @@ extension JSClassMacro: MemberMacro {
         }
 
         var members: [DeclSyntax] = []
+        guard let structDecl = declaration.as(StructDeclSyntax.self) else { return members }
+
+        if let accessLevel = accessLevel(from: structDecl.modifiers),
+            accessLevel == .private || accessLevel == .fileprivate
+        {
+            context.diagnose(
+                Diagnostic(
+                    node: Syntax(structDecl),
+                    message: JSMacroMessage.jsClassRequiresAtLeastInternal
+                )
+            )
+            return []
+        }
+
+        let memberAccessModifier = synthesizedMemberAccessModifier(for: declaration).map { "\($0) " } ?? ""
 
         let existingMembers = declaration.memberBlock.members
         let hasJSObjectProperty = existingMembers.contains { member in
@@ -57,7 +72,7 @@ extension JSClassMacro: MemberMacro {
         }
 
         if !hasJSObjectProperty {
-            members.append(DeclSyntax("let jsObject: JSObject"))
+            members.append(DeclSyntax("\(raw: memberAccessModifier)let jsObject: JSObject"))
         }
 
         let hasUnsafelyWrappingInit = existingMembers.contains { member in
@@ -73,7 +88,7 @@ extension JSClassMacro: MemberMacro {
             members.append(
                 DeclSyntax(
                     """
-                    init(unsafelyWrapping jsObject: JSObject) {
+                    \(raw: memberAccessModifier)init(unsafelyWrapping jsObject: JSObject) {
                         self.jsObject = jsObject
                     }
                     """
@@ -95,6 +110,11 @@ extension JSClassMacro: ExtensionMacro {
     ) throws -> [ExtensionDeclSyntax] {
         guard let structDecl = declaration.as(StructDeclSyntax.self) else { return [] }
         guard !protocols.isEmpty else { return [] }
+        if let accessLevel = accessLevel(from: structDecl.modifiers),
+            accessLevel == .private || accessLevel == .fileprivate
+        {
+            return []
+        }
 
         // Do not add extension if the struct already conforms to _JSBridgedClass
         if let clause = structDecl.inheritanceClause,
@@ -108,4 +128,37 @@ extension JSClassMacro: ExtensionMacro {
             try ExtensionDeclSyntax("extension \(type.trimmed): \(raw: conformanceList) {}")
         ]
     }
+
+    private static func synthesizedMemberAccessModifier(for declaration: some DeclGroupSyntax) -> String? {
+        guard let structDecl = declaration.as(StructDeclSyntax.self) else { return nil }
+        switch accessLevel(from: structDecl.modifiers) {
+        case .public: return "public"
+        case .package: return "package"
+        case .internal: return "internal"
+        case .fileprivate, .private, .none: return nil
+        }
+    }
+
+    private enum AccessLevel {
+        case `public`
+        case package
+        case `internal`
+        case `fileprivate`
+        case `private`
+    }
+
+    private static func accessLevel(from modifiers: DeclModifierListSyntax?) -> AccessLevel? {
+        guard let modifiers else { return nil }
+        for modifier in modifiers {
+            switch modifier.name.tokenKind {
+            case .keyword(.public): return .public
+            case .keyword(.package): return .package
+            case .keyword(.internal): return .internal
+            case .keyword(.fileprivate): return .fileprivate
+            case .keyword(.private): return .private
+            default: continue
+            }
+        }
+        return nil
+    }
 }
diff --git a/Plugins/BridgeJS/Sources/BridgeJSMacros/JSMacroSupport.swift b/Plugins/BridgeJS/Sources/BridgeJSMacros/JSMacroSupport.swift
@@ -14,6 +14,10 @@ enum JSMacroMessage: String, DiagnosticMessage {
     case setterRequiresThrows = "@JSSetter function must declare throws(JSException)."
     case jsFunctionRequiresThrows = "@JSFunction throws must be declared as throws(JSException)."
     case requiresJSClass = "JavaScript members must be declared inside a @JSClass struct."
+    case jsClassRequiresAtLeastInternal =
+        "@JSClass does not support private/fileprivate access level. Use internal, package, or public."
+    case jsClassMemberRequiresAtLeastInternal =
+        "@JSClass requires jsObject and init(unsafelyWrapping:) to be at least internal."
 
     var message: String { rawValue }
     var diagnosticID: MessageID { MessageID(domain: "JavaScriptKitMacros", id: rawValue) }

diff --git a/Plugins/BridgeJS/Tests/BridgeJSMacrosTests/JSClassMacroTests.swift b/Plugins/BridgeJS/Tests/BridgeJSMacrosTests/JSClassMacroTests.swift
@@ -370,4 +370,102 @@ import BridgeJSMacros
             indentationWidth: indentationWidth
         )
     }
+
+    @Test func publicStructSynthesizesPublicMembers() {
+        TestSupport.assertMacroExpansion(
+            """
+            @JSClass
+            public struct MyClass {
+            }
+            """,
+            expandedSource: """
+                public struct MyClass {
+
+                    public let jsObject: JSObject
+
+                    public init(unsafelyWrapping jsObject: JSObject) {
+                        self.jsObject = jsObject
+                    }
+                }
+
+                extension MyClass: _JSBridgedClass {
+                }
+                """,
+            macroSpecs: macroSpecs,
+            indentationWidth: indentationWidth
+        )
+    }
+
+    @Test func packageStructSynthesizesPackageMembers() {
+        TestSupport.assertMacroExpansion(
+            """
+            @JSClass
+            package struct MyClass {
+            }
+            """,
+            expandedSource: """
+                package struct MyClass {
+
+                    package let jsObject: JSObject
+
+                    package init(unsafelyWrapping jsObject: JSObject) {
+                        self.jsObject = jsObject
+                    }
+                }
+
+                extension MyClass: _JSBridgedClass {
+                }
+                """,
+            macroSpecs: macroSpecs,
+            indentationWidth: indentationWidth
+        )
+    }
+
+    @Test func privateStructIsRejected() {
+        TestSupport.assertMacroExpansion(
+            """
+            @JSClass
+            private struct MyClass {
+            }
+            """,
+            expandedSource: """
+                private struct MyClass {
+                }
+                """,
+            diagnostics: [
+                DiagnosticSpec(
+                    message:
+                        "@JSClass does not support private/fileprivate access level. Use internal, package, or public.",
+                    line: 1,
+                    column: 1
+                )
+            ],
+            macroSpecs: macroSpecs,
+            indentationWidth: indentationWidth
+        )
+    }
+
+    @Test func fileprivateStructIsRejected() {
+        TestSupport.assertMacroExpansion(
+            """
+            @JSClass
+            fileprivate struct MyClass {
+            }
+            """,
+            expandedSource: """
+                fileprivate struct MyClass {
+                }
+                """,
+            diagnostics: [
+                DiagnosticSpec(
+                    message:
+                        "@JSClass does not support private/fileprivate access level. Use internal, package, or public.",
+                    line: 1,
+                    column: 1
+                )
+            ],
+            macroSpecs: macroSpecs,
+            indentationWidth: indentationWidth
+        )
+    }
 }
diff --git a/Tests/BridgeJSRuntimeTests/Generated/BridgeJS.swift b/Tests/BridgeJSRuntimeTests/Generated/BridgeJS.swift
@@ -10156,6 +10156,137 @@ func _$jsTranslatePoint(_ point: Point, _ dx: Int, _ dy: Int) throws(JSException
     return Point.bridgeJSLiftReturn(ret)
 }
 
+#if arch(wasm32)
+@_extern(wasm, module: "BridgeJSRuntimeTests", name: "bjs_MyJSClassInternal_init")
+fileprivate func bjs_MyJSClassInternal_init() -> Int32
+#else
+fileprivate func bjs_MyJSClassInternal_init() -> Int32 {
+    fatalError("Only available on WebAssembly")
+}
+#endif
+
+func _$MyJSClassInternal_init() throws(JSException) -> JSObject {
+    let ret = bjs_MyJSClassInternal_init()
+    if let error = _swift_js_take_exception() {
+        throw error
+    }
+    return JSObject.bridgeJSLiftReturn(ret)
+}
+
+#if arch(wasm32)
+@_extern(wasm, module: "BridgeJSRuntimeTests", name: "bjs_MyJSClassPublic_init")
+fileprivate func bjs_MyJSClassPublic_init() -> Int32
+#else
+fileprivate func bjs_MyJSClassPublic_init() -> Int32 {
+    fatalError("Only available on WebAssembly")
+}
+#endif
+
+func _$MyJSClassPublic_init() throws(JSException) -> JSObject {
+    let ret = bjs_MyJSClassPublic_init()
+    if let error = _swift_js_take_exception() {
+        throw error
+    }
+    return JSObject.bridgeJSLiftReturn(ret)
+}
+
+#if arch(wasm32)
+@_extern(wasm, module: "BridgeJSRuntimeTests", name: "bjs_MyJSClassPackage_init")
+fileprivate func bjs_MyJSClassPackage_init() -> Int32
+#else
+fileprivate func bjs_MyJSClassPackage_init() -> Int32 {
+    fatalError("Only available on WebAssembly")
+}
+#endif
+
+func _$MyJSClassPackage_init() throws(JSException) -> JSObject {
+    let ret = bjs_MyJSClassPackage_init()
+    if let error = _swift_js_take_exception() {
+        throw error
+    }
+    return JSObject.bridgeJSLiftReturn(ret)
+}
+
+#if arch(wasm32)
+@_extern(wasm, module: "BridgeJSRuntimeTests", name: "bjs_jsFunctionWithPackageAccess")
+fileprivate func bjs_jsFunctionWithPackageAccess() -> Void
+#else
+fileprivate func bjs_jsFunctionWithPackageAccess() -> Void {
+    fatalError("Only available on WebAssembly")
+}
+#endif
+
+func _$jsFunctionWithPackageAccess() throws(JSException) -> Void {
+    bjs_jsFunctionWithPackageAccess()
+    if let error = _swift_js_take_exception() {
+        throw error
+    }
+}
+
+#if arch(wasm32)
+@_extern(wasm, module: "BridgeJSRuntimeTests", name: "bjs_jsFunctionWithPublicAccess")
+fileprivate func bjs_jsFunctionWithPublicAccess() -> Void
+#else
+fileprivate func bjs_jsFunctionWithPublicAccess() -> Void {
+    fatalError("Only available on WebAssembly")
+}
+#endif
+
+func _$jsFunctionWithPublicAccess() throws(JSException) -> Void {
+    bjs_jsFunctionWithPublicAccess()
+    if let error = _swift_js_take_exception() {
+        throw error
+    }
+}
+
+#if arch(wasm32)
+@_extern(wasm, module: "BridgeJSRuntimeTests", name: "bjs_jsFunctionWithInternalAccess")
+fileprivate func bjs_jsFunctionWithInternalAccess() -> Void
+#else
+fileprivate func bjs_jsFunctionWithInternalAccess() -> Void {
+    fatalError("Only available on WebAssembly")
+}
+#endif
+
+func _$jsFunctionWithInternalAccess() throws(JSException) -> Void {
+    bjs_jsFunctionWithInternalAccess()
+    if let error = _swift_js_take_exception() {
+        throw error
+    }
+}
+
+#if arch(wasm32)
+@_extern(wasm, module: "BridgeJSRuntimeTests", name: "bjs_jsFunctionWithFilePrivateAccess")
+fileprivate func bjs_jsFunctionWithFilePrivateAccess() -> Void
+#else
+fileprivate func bjs_jsFunctionWithFilePrivateAccess() -> Void {
+    fatalError("Only available on WebAssembly")
+}
+#endif
+
+func _$jsFunctionWithFilePrivateAccess() throws(JSException) -> Void {
+    bjs_jsFunctionWithFilePrivateAccess()
+    if let error = _swift_js_take_exception() {
+        throw error
+    }
+}
+
+#if arch(wasm32)
+@_extern(wasm, module: "BridgeJSRuntimeTests", name: "bjs_jsFunctionWithPrivateAccess")
+fileprivate func bjs_jsFunctionWithPrivateAccess() -> Void
+#else
+fileprivate func bjs_jsFunctionWithPrivateAccess() -> Void {
+    fatalError("Only available on WebAssembly")
+}
+#endif
+
+func _$jsFunctionWithPrivateAccess() throws(JSException) -> Void {
+    bjs_jsFunctionWithPrivateAccess()
+    if let error = _swift_js_take_exception() {
+        throw error
+    }
+}
+
 #if arch(wasm32)
 @_extern(wasm, module: "BridgeJSRuntimeTests", name: "bjs_OptionalSupportImports_jsRoundTripOptionalNumberNull_static")
 fileprivate func bjs_OptionalSupportImports_jsRoundTripOptionalNumberNull_static(_ valueIsSome: Int32, _ valueValue: Int32) -> Void