BridgeJS: allow @js structs to copy from JSObject

Add struct-level helpers for copying values out of a backing JS object and raising a new JS object from a Swift struct.

This makes it possible to round-trip JSON-style plain objects without manual field mapping, while keeping the default value semantics of exported structs.

Author: kateinoigakukun

Benchmarks/Sources/Generated/BridgeJS.swift

@@ -267,7 +267,49 @@ extension SimpleStruct: _BridgedSwiftStruct {
         _swift_js_push_f32(self.rate)
         _swift_js_push_f64(self.precise)
     }
+
+    init(unsafelyCopying jsObject: JSObject) {
+        let __bjs_cleanupId = _SimpleStructHelpers.lower(jsObject)
+        defer {
+            _swift_js_struct_cleanup(__bjs_cleanupId)
+        }
+        self = Self.bridgeJSLiftParameter()
+    }
+
+    func toJSObject() -> JSObject {
+        var __bjs_self = self
+        __bjs_self.bridgeJSLowerReturn()
+        return _SimpleStructHelpers.raise()
+    }
+}
+
+fileprivate enum _SimpleStructHelpers {
+    static func lower(_ jsObject: JSObject) -> Int32 {
+        return _bjs_struct_lower_SimpleStruct(jsObject.bridgeJSLowerParameter())
+    }
+
+    static func raise() -> JSObject {
+        return JSObject(id: UInt32(bitPattern: _bjs_struct_raise_SimpleStruct()))
+    }
+}
+
+#if arch(wasm32)
+@_extern(wasm, module: "bjs", name: "swift_js_struct_lower_SimpleStruct")
+fileprivate func _bjs_struct_lower_SimpleStruct(_ objectId: Int32) -> Int32
+#else
+fileprivate func _bjs_struct_lower_SimpleStruct(_ objectId: Int32) -> Int32 {
+    fatalError("Only available on WebAssembly")
 }
+#endif
+
+#if arch(wasm32)
+@_extern(wasm, module: "bjs", name: "swift_js_struct_raise_SimpleStruct")
+fileprivate func _bjs_struct_raise_SimpleStruct() -> Int32
+#else
+fileprivate func _bjs_struct_raise_SimpleStruct() -> Int32 {
+    fatalError("Only available on WebAssembly")
+}
+#endif
 
 extension Address: _BridgedSwiftStruct {
     @_spi(BridgeJS) @_transparent public static func bridgeJSLiftParameter() -> Address {
@@ -288,7 +330,49 @@ extension Address: _BridgedSwiftStruct {
         }
         _swift_js_push_int(Int32(self.zipCode))
     }
+
+    init(unsafelyCopying jsObject: JSObject) {
+        let __bjs_cleanupId = _AddressHelpers.lower(jsObject)
+        defer {
+            _swift_js_struct_cleanup(__bjs_cleanupId)
+        }
+        self = Self.bridgeJSLiftParameter()
+    }
+
+    func toJSObject() -> JSObject {
+        var __bjs_self = self
+        __bjs_self.bridgeJSLowerReturn()
+        return _AddressHelpers.raise()
+    }
+}
+
+fileprivate enum _AddressHelpers {
+    static func lower(_ jsObject: JSObject) -> Int32 {
+        return _bjs_struct_lower_Address(jsObject.bridgeJSLowerParameter())
+    }
+
+    static func raise() -> JSObject {
+        return JSObject(id: UInt32(bitPattern: _bjs_struct_raise_Address()))
+    }
+}
+
+#if arch(wasm32)
+@_extern(wasm, module: "bjs", name: "swift_js_struct_lower_Address")
+fileprivate func _bjs_struct_lower_Address(_ objectId: Int32) -> Int32
+#else
+fileprivate func _bjs_struct_lower_Address(_ objectId: Int32) -> Int32 {
+    fatalError("Only available on WebAssembly")
 }
+#endif
+
+#if arch(wasm32)
+@_extern(wasm, module: "bjs", name: "swift_js_struct_raise_Address")
+fileprivate func _bjs_struct_raise_Address() -> Int32
+#else
+fileprivate func _bjs_struct_raise_Address() -> Int32 {
+    fatalError("Only available on WebAssembly")
+}
+#endif
 
 extension Person: _BridgedSwiftStruct {
     @_spi(BridgeJS) @_transparent public static func bridgeJSLiftParameter() -> Person {
@@ -315,7 +399,49 @@ extension Person: _BridgedSwiftStruct {
         }
         _swift_js_push_int(__bjs_isSome_email ? 1 : 0)
     }
+
+    init(unsafelyCopying jsObject: JSObject) {
+        let __bjs_cleanupId = _PersonHelpers.lower(jsObject)
+        defer {
+            _swift_js_struct_cleanup(__bjs_cleanupId)
+        }
+        self = Self.bridgeJSLiftParameter()
+    }
+
+    func toJSObject() -> JSObject {
+        var __bjs_self = self
+        __bjs_self.bridgeJSLowerReturn()
+        return _PersonHelpers.raise()
+    }
+}
+
+fileprivate enum _PersonHelpers {
+    static func lower(_ jsObject: JSObject) -> Int32 {
+        return _bjs_struct_lower_Person(jsObject.bridgeJSLowerParameter())
+    }
+
+    static func raise() -> JSObject {
+        return JSObject(id: UInt32(bitPattern: _bjs_struct_raise_Person()))
+    }
+}
+
+#if arch(wasm32)
+@_extern(wasm, module: "bjs", name: "swift_js_struct_lower_Person")
+fileprivate func _bjs_struct_lower_Person(_ objectId: Int32) -> Int32
+#else
+fileprivate func _bjs_struct_lower_Person(_ objectId: Int32) -> Int32 {
+    fatalError("Only available on WebAssembly")
 }
+#endif
+
+#if arch(wasm32)
+@_extern(wasm, module: "bjs", name: "swift_js_struct_raise_Person")
+fileprivate func _bjs_struct_raise_Person() -> Int32
+#else
+fileprivate func _bjs_struct_raise_Person() -> Int32 {
+    fatalError("Only available on WebAssembly")
+}
+#endif
 
 extension ComplexStruct: _BridgedSwiftStruct {
     @_spi(BridgeJS) @_transparent public static func bridgeJSLiftParameter() -> ComplexStruct {
@@ -345,7 +471,49 @@ extension ComplexStruct: _BridgedSwiftStruct {
             _swift_js_push_string(ptr.baseAddress, Int32(ptr.count))
         }
     }
+
+    init(unsafelyCopying jsObject: JSObject) {
+        let __bjs_cleanupId = _ComplexStructHelpers.lower(jsObject)
+        defer {
+            _swift_js_struct_cleanup(__bjs_cleanupId)
+        }
+        self = Self.bridgeJSLiftParameter()
+    }
+
+    func toJSObject() -> JSObject {
+        var __bjs_self = self
+        __bjs_self.bridgeJSLowerReturn()
+        return _ComplexStructHelpers.raise()
+    }
+}
+
+fileprivate enum _ComplexStructHelpers {
+    static func lower(_ jsObject: JSObject) -> Int32 {
+        return _bjs_struct_lower_ComplexStruct(jsObject.bridgeJSLowerParameter())
+    }
+
+    static func raise() -> JSObject {
+        return JSObject(id: UInt32(bitPattern: _bjs_struct_raise_ComplexStruct()))
+    }
+}
+
+#if arch(wasm32)
+@_extern(wasm, module: "bjs", name: "swift_js_struct_lower_ComplexStruct")
+fileprivate func _bjs_struct_lower_ComplexStruct(_ objectId: Int32) -> Int32
+#else
+fileprivate func _bjs_struct_lower_ComplexStruct(_ objectId: Int32) -> Int32 {
+    fatalError("Only available on WebAssembly")
 }
+#endif
+
+#if arch(wasm32)
+@_extern(wasm, module: "bjs", name: "swift_js_struct_raise_ComplexStruct")
+fileprivate func _bjs_struct_raise_ComplexStruct() -> Int32
+#else
+fileprivate func _bjs_struct_raise_ComplexStruct() -> Int32 {
+    fatalError("Only available on WebAssembly")
+}
+#endif
 
 @_expose(wasm, "bjs_run")
 @_cdecl("bjs_run")

Plugins/BridgeJS/Sources/BridgeJSCore/ExportSwift.swift

@@ -74,7 +74,7 @@ public class ExportSwift {
 
         let structCodegen = StructCodegen()
         for structDef in skeleton.structs {
-            decls.append(structCodegen.renderStructHelpers(structDef))
+            decls.append(contentsOf: structCodegen.renderStructHelpers(structDef))
             decls.append(contentsOf: try renderSingleExportedStruct(struct: structDef))
         }
 
@@ -1147,12 +1147,19 @@ struct EnumCodegen {
 struct StructCodegen {
     private let stackCodegen = StackCodegen()
 
-    func renderStructHelpers(_ structDef: ExportedStruct) -> DeclSyntax {
+    func renderStructHelpers(_ structDef: ExportedStruct) -> [DeclSyntax] {
         let typeName = structDef.swiftCallName
         let liftCode = generateStructLiftCode(structDef: structDef)
         let lowerCode = generateStructLowerCode(structDef: structDef)
+        let accessControl = structDef.explicitAccessControl.map { "\($0) " } ?? ""
 
-        return """
+        let helpersTypeName = "_\(structDef.name)Helpers"
+        let lowerExternName = "swift_js_struct_lower_\(structDef.name)"
+        let raiseExternName = "swift_js_struct_raise_\(structDef.name)"
+        let lowerFunctionName = "_bjs_struct_lower_\(structDef.name)"
+        let raiseFunctionName = "_bjs_struct_raise_\(structDef.name)"
+
+        let bridgedStructExtension: DeclSyntax = """
             extension \(raw: typeName): _BridgedSwiftStruct {
                 @_spi(BridgeJS) @_transparent public static func bridgeJSLiftParameter() -> \(raw: typeName) {
                     \(raw: liftCode.joined(separator: "\n"))
@@ -1161,8 +1168,83 @@ struct StructCodegen {
                 @_spi(BridgeJS) @_transparent public consuming func bridgeJSLowerReturn() {
                     \(raw: lowerCode.joined(separator: "\n"))
                 }
+
+                \(raw: accessControl)init(unsafelyCopying jsObject: JSObject) {
+                    let __bjs_cleanupId = \(raw: helpersTypeName).lower(jsObject)
+                    defer { _swift_js_struct_cleanup(__bjs_cleanupId) }
+                    self = Self.bridgeJSLiftParameter()
+                }
+
+                \(raw: accessControl)func toJSObject() -> JSObject {
+                    var __bjs_self = self
+                    __bjs_self.bridgeJSLowerReturn()
+                    return \(raw: helpersTypeName).raise()
+                }
             }
             """
+
+        let helpersType: DeclSyntax = """
+            fileprivate enum \(raw: helpersTypeName) {
+                static func lower(_ jsObject: JSObject) -> Int32 {
+                    return \(raw: lowerFunctionName)(jsObject.bridgeJSLowerParameter())
+                }
+
+                static func raise() -> JSObject {
+                    return JSObject(id: UInt32(bitPattern: \(raw: raiseFunctionName)()))
+                }
+            }
+            """
+
+        let lowerExternDecl = Self.renderStructExtern(
+            externName: lowerExternName,
+            functionName: lowerFunctionName,
+            signature: SwiftSignatureBuilder.buildABIFunctionSignature(
+                abiParameters: [("objectId", .i32)],
+                returnType: .i32
+            )
+        )
+        let raiseExternDecl = Self.renderStructExtern(
+            externName: raiseExternName,
+            functionName: raiseFunctionName,
+            signature: SwiftSignatureBuilder.buildABIFunctionSignature(
+                abiParameters: [],
+                returnType: .i32
+            )
+        )
+
+        return [bridgedStructExtension, helpersType, lowerExternDecl, raiseExternDecl]
+    }
+
+    private static func renderStructExtern(
+        externName: String,
+        functionName: String,
+        signature: FunctionSignatureSyntax
+    ) -> DeclSyntax {
+        let externFuncDecl = SwiftCodePattern.buildExternFunctionDecl(
+            moduleName: "bjs",
+            abiName: externName,
+            functionName: functionName,
+            signature: signature
+        )
+
+        let stubFuncDecl = FunctionDeclSyntax(
+            modifiers: DeclModifierListSyntax {
+                DeclModifierSyntax(name: .keyword(.fileprivate))
+            },
+            funcKeyword: .keyword(.func),
+            name: .identifier(functionName),
+            signature: signature,
+            body: CodeBlockSyntax {
+                "fatalError(\"Only available on WebAssembly\")"
+            }
+        )
+
+        return DeclSyntax(
+            SwiftCodePattern.buildWasmConditionalCompilationDecls(
+                wasmDecl: DeclSyntax(externFuncDecl),
+                elseDecl: DeclSyntax(stubFuncDecl)
+            )
+        )
     }
 
     private func generateStructLiftCode(structDef: ExportedStruct) -> [String] {

Plugins/BridgeJS/Sources/BridgeJSLink/BridgeJSLink.swift

@@ -245,6 +245,7 @@ public struct BridgeJSLink {
             "let \(JSGlueVariableScope.reservedTmpParamF64s) = [];",
             "let \(JSGlueVariableScope.reservedTmpRetPointers) = [];",
             "let \(JSGlueVariableScope.reservedTmpParamPointers) = [];",
+            "let \(JSGlueVariableScope.reservedTmpStructCleanups) = [];",
             "const \(JSGlueVariableScope.reservedEnumHelpers) = {};",
             "const \(JSGlueVariableScope.reservedStructHelpers) = {};",
             "",
@@ -295,6 +296,7 @@ public struct BridgeJSLink {
 
     private func generateAddImports() -> CodeFragmentPrinter {
         let printer = CodeFragmentPrinter()
+        let allStructs = skeletons.compactMap { $0.exported?.structs }.flatMap { $0 }
         printer.write("return {")
         printer.indent {
             printer.write(lines: [
@@ -427,6 +429,53 @@ public struct BridgeJSLink {
                     printer.write("return \(JSGlueVariableScope.reservedTmpParamPointers).pop();")
                 }
                 printer.write("}")
+
+                printer.write("bjs[\"swift_js_struct_cleanup\"] = function(cleanupId) {")
+                printer.indent {
+                    printer.write("if (cleanupId === 0) { return; }")
+                    printer.write("const index = (cleanupId | 0) - 1;")
+                    printer.write("const cleanup = \(JSGlueVariableScope.reservedTmpStructCleanups)[index];")
+                    printer.write("\(JSGlueVariableScope.reservedTmpStructCleanups)[index] = null;")
+                    printer.write("if (cleanup) { cleanup(); }")
+                    printer.write(
+                        "while (\(JSGlueVariableScope.reservedTmpStructCleanups).length > 0 && \(JSGlueVariableScope.reservedTmpStructCleanups)[\(JSGlueVariableScope.reservedTmpStructCleanups).length - 1] == null) {"
+                    )
+                    printer.indent {
+                        printer.write("\(JSGlueVariableScope.reservedTmpStructCleanups).pop();")
+                    }
+                    printer.write("}")
+                }
+                printer.write("}")
+
+                if !allStructs.isEmpty {
+                    for structDef in allStructs {
+                        printer.write("bjs[\"swift_js_struct_lower_\(structDef.name)\"] = function(objectId) {")
+                        printer.indent {
+                            printer.write(
+                                "const { cleanup: cleanup } = \(JSGlueVariableScope.reservedStructHelpers).\(structDef.name).lower(\(JSGlueVariableScope.reservedSwift).memory.getObject(objectId));"
+                            )
+                            printer.write("if (cleanup) {")
+                            printer.indent {
+                                printer.write(
+                                    "return \(JSGlueVariableScope.reservedTmpStructCleanups).push(cleanup);"
+                                )
+                            }
+                            printer.write("}")
+                            printer.write("return 0;")
+                        }
+                        printer.write("}")
+
+                        printer.write("bjs[\"swift_js_struct_raise_\(structDef.name)\"] = function() {")
+                        printer.indent {
+                            printer.write(
+                                "const value = \(JSGlueVariableScope.reservedStructHelpers).\(structDef.name).raise(\(JSGlueVariableScope.reservedTmpRetStrings), \(JSGlueVariableScope.reservedTmpRetInts), \(JSGlueVariableScope.reservedTmpRetF32s), \(JSGlueVariableScope.reservedTmpRetF64s), \(JSGlueVariableScope.reservedTmpRetPointers));"
+                            )
+                            printer.write("return \(JSGlueVariableScope.reservedSwift).memory.retain(value);")
+                        }
+                        printer.write("}")
+                    }
+                }
+
                 printer.write("bjs[\"swift_js_return_optional_bool\"] = function(isSome, value) {")
                 printer.indent {
                     printer.write("if (isSome === 0) {")