BridgeJS: Support generic functions on imported JS APIs

Author: krodak

Benchmarks/Sources/Generated/BridgeJS.swift

@@ -2179,6 +2179,34 @@ fileprivate func _bjs_ArrayRoundtrip_wrap_extern(_ pointer: UnsafeMutableRawPoin
     return _bjs_ArrayRoundtrip_wrap_extern(pointer)
 }
 
+extension SimpleStruct: BridgedSwiftGenericBridgeable {
+    @_spi(BridgeJS) public static let bridgeJSTypeHandle = SimpleStruct.bridgeJSMakeTypeHandle()
+}
+
+extension Address: BridgedSwiftGenericBridgeable {
+    @_spi(BridgeJS) public static let bridgeJSTypeHandle = Address.bridgeJSMakeTypeHandle()
+}
+
+extension Person: BridgedSwiftGenericBridgeable {
+    @_spi(BridgeJS) public static let bridgeJSTypeHandle = Person.bridgeJSMakeTypeHandle()
+}
+
+extension ComplexStruct: BridgedSwiftGenericBridgeable {
+    @_spi(BridgeJS) public static let bridgeJSTypeHandle = ComplexStruct.bridgeJSMakeTypeHandle()
+}
+
+extension Point: BridgedSwiftGenericBridgeable {
+    @_spi(BridgeJS) public static let bridgeJSTypeHandle = Point.bridgeJSMakeTypeHandle()
+}
+
+extension APIResult: BridgedSwiftGenericBridgeable {
+    @_spi(BridgeJS) public static let bridgeJSTypeHandle = APIResult.bridgeJSMakeTypeHandle()
+}
+
+extension ComplexResult: BridgedSwiftGenericBridgeable {
+    @_spi(BridgeJS) public static let bridgeJSTypeHandle = ComplexResult.bridgeJSMakeTypeHandle()
+}
+
 #if arch(wasm32)
 @_extern(wasm, module: "Benchmarks", name: "bjs_benchmarkHelperNoop")
 fileprivate func bjs_benchmarkHelperNoop_extern() -> Void
@@ -2238,4 +2266,40 @@ func _$benchmarkRunner(_ name: String, _ body: JSObject) throws(JSException) ->
     if let error = _swift_js_take_exception() {
         throw error
     }
-}
+}
+
+#if arch(wasm32)
+@_extern(wasm, module: "bjs", name: "bjs_Benchmarks_register_type_handles")
+fileprivate func _bjs_Benchmarks_register_type_handles_extern(_ base: UnsafePointer<Int32>?, _ count: Int32)
+
+@_expose(wasm, "bjs_Benchmarks_register_type_handles")
+public func _bjs_Benchmarks_register_type_handles() {
+    let typeIds: [Int32] = [
+        Bool.bridgeJSTypeID,
+        Int.bridgeJSTypeID,
+        Int8.bridgeJSTypeID,
+        UInt8.bridgeJSTypeID,
+        Int16.bridgeJSTypeID,
+        UInt16.bridgeJSTypeID,
+        Int32.bridgeJSTypeID,
+        UInt32.bridgeJSTypeID,
+        UInt.bridgeJSTypeID,
+        Int64.bridgeJSTypeID,
+        UInt64.bridgeJSTypeID,
+        Float.bridgeJSTypeID,
+        Double.bridgeJSTypeID,
+        String.bridgeJSTypeID,
+        JSValue.bridgeJSTypeID,
+        SimpleStruct.bridgeJSTypeID,
+        Address.bridgeJSTypeID,
+        Person.bridgeJSTypeID,
+        ComplexStruct.bridgeJSTypeID,
+        Point.bridgeJSTypeID,
+        APIResult.bridgeJSTypeID,
+        ComplexResult.bridgeJSTypeID,
+    ]
+    typeIds.withUnsafeBufferPointer { buffer in
+        _bjs_Benchmarks_register_type_handles_extern(buffer.baseAddress, Int32(buffer.count))
+    }
+}
+#endif

Examples/Embedded/Package.swift

@@ -16,6 +16,9 @@ let package = Package(
             swiftSettings: [
                 .enableExperimentalFeature("Extern")
             ],
+            plugins: [
+                .plugin(name: "BridgeJS", package: "JavaScriptKit")
+            ]
         )
     ],
     swiftLanguageModes: [.v5]

Examples/Embedded/Sources/EmbeddedApp/main.swift

@@ -1,5 +1,15 @@
 import JavaScriptKit
 
+// BridgeJS generic imports work under Embedded Swift: `echoValue` is
+// implemented in JavaScript (see index.html) and a single piece of generated
+// glue serves every conforming type, selected by a runtime type ID.
+@JS struct CounterLabel {
+    var count: Int
+    var text: String
+}
+
+@JSFunction func echoValue<T: BridgedSwiftGenericBridgeable>(_ value: T) throws(JSException) -> T
+
 let alert = JSObject.global.alert.object!
 let document = JSObject.global.document
 
@@ -46,6 +56,17 @@ _ = encoderContainer.appendChild(textInputElement)
 _ = encoderContainer.appendChild(encodeResultElement)
 _ = document.body.appendChild(encoderContainer)
 
+let genericResultElement = document.createElement("pre")
+do {
+    let number = try echoValue(42)
+    let text = try echoValue("hello")
+    let label = try echoValue(CounterLabel(count: number, text: text))
+    genericResultElement.innerText = .string("Generic import round-trip: \(label.text) \(label.count)")
+} catch {
+    genericResultElement.innerText = "Generic import round-trip failed"
+}
+_ = document.body.appendChild(genericResultElement)
+
 func print(_ message: String) {
     _ = JSObject.global.console.log(message)
 }

Examples/Embedded/index.html

@@ -8,7 +8,14 @@
 <body>
   <script type="module">
     import { init } from "./.build/plugins/PackageToJS/outputs/Package/index.js";
-    init();
+    init({
+      getImports() {
+        return {
+          // Implements the generic `echoValue` imported by main.swift.
+          echoValue: (value) => value,
+        };
+      },
+    });
   </script>
 </body>
 

Examples/PlayBridgeJS/Sources/PlayBridgeJS/Generated/BridgeJS.swift

@@ -231,6 +231,18 @@ fileprivate func _bjs_PlayBridgeJS_wrap_extern(_ pointer: UnsafeMutableRawPointe
     return _bjs_PlayBridgeJS_wrap_extern(pointer)
 }
 
+extension PlayBridgeJSOutput: BridgedSwiftGenericBridgeable {
+    @_spi(BridgeJS) public static let bridgeJSTypeHandle = PlayBridgeJSOutput.bridgeJSMakeTypeHandle()
+}
+
+extension PlayBridgeJSDiagnostic: BridgedSwiftGenericBridgeable {
+    @_spi(BridgeJS) public static let bridgeJSTypeHandle = PlayBridgeJSDiagnostic.bridgeJSMakeTypeHandle()
+}
+
+extension PlayBridgeJSResult: BridgedSwiftGenericBridgeable {
+    @_spi(BridgeJS) public static let bridgeJSTypeHandle = PlayBridgeJSResult.bridgeJSMakeTypeHandle()
+}
+
 #if arch(wasm32)
 @_extern(wasm, module: "PlayBridgeJS", name: "bjs_createTS2Swift")
 fileprivate func bjs_createTS2Swift_extern() -> Int32
@@ -274,4 +286,36 @@ func _$TS2Swift_convert(_ self: JSObject, _ ts: String) throws(JSException) -> S
         throw error
     }
     return String.bridgeJSLiftReturn(ret)
-}
+}
+
+#if arch(wasm32)
+@_extern(wasm, module: "bjs", name: "bjs_PlayBridgeJS_register_type_handles")
+fileprivate func _bjs_PlayBridgeJS_register_type_handles_extern(_ base: UnsafePointer<Int32>?, _ count: Int32)
+
+@_expose(wasm, "bjs_PlayBridgeJS_register_type_handles")
+public func _bjs_PlayBridgeJS_register_type_handles() {
+    let typeIds: [Int32] = [
+        Bool.bridgeJSTypeID,
+        Int.bridgeJSTypeID,
+        Int8.bridgeJSTypeID,
+        UInt8.bridgeJSTypeID,
+        Int16.bridgeJSTypeID,
+        UInt16.bridgeJSTypeID,
+        Int32.bridgeJSTypeID,
+        UInt32.bridgeJSTypeID,
+        UInt.bridgeJSTypeID,
+        Int64.bridgeJSTypeID,
+        UInt64.bridgeJSTypeID,
+        Float.bridgeJSTypeID,
+        Double.bridgeJSTypeID,
+        String.bridgeJSTypeID,
+        JSValue.bridgeJSTypeID,
+        PlayBridgeJSOutput.bridgeJSTypeID,
+        PlayBridgeJSDiagnostic.bridgeJSTypeID,
+        PlayBridgeJSResult.bridgeJSTypeID,
+    ]
+    typeIds.withUnsafeBufferPointer { buffer in
+        _bjs_PlayBridgeJS_register_type_handles_extern(buffer.baseAddress, Int32(buffer.count))
+    }
+}
+#endif

Plugins/BridgeJS/README.md

@@ -98,7 +98,7 @@ graph LR
 | `Dictionary<K, V>` | `Record<K, V>` | - | [#495](https://github.com/swiftwasm/JavaScriptKit/issues/495) |
 | `Set<T>` | `Set<T>` | - | [#397](https://github.com/swiftwasm/JavaScriptKit/issues/397) |
 | `Foundation.URL` | `string` | - | [#496](https://github.com/swiftwasm/JavaScriptKit/issues/496) |
-| Generics | - | - | [#398](https://github.com/swiftwasm/JavaScriptKit/issues/398) |
+| Generic function or method (`T`, `[T]`, `T?`, `[String: T]`) | `<T>(value: T): T` | Depends on `T` | ✅ imports only ([#398](https://github.com/swiftwasm/JavaScriptKit/issues/398) for exports) |
 
 ### Import-specific (TypeScript -> Swift)
 

Plugins/BridgeJS/Sources/BridgeJSCore/ExportSwift.swift

@@ -91,6 +91,15 @@ public class ExportSwift {
             }
         }
 
+        withSpan("Render Generic Bridgeable Conformances") { [self] in
+            // Emitted unconditionally: a module cannot know whether a dependent
+            // module passes its types to a generic imported function.
+            let genericConformanceCodegen = GenericConformanceCodegen()
+            for entry in skeleton.genericBridgeableTypeEntries {
+                decls.append(contentsOf: genericConformanceCodegen.renderConformance(typeName: entry.swiftName))
+            }
+        }
+
         try withSpan("Render Async Promise Helpers") { [self] in
             let asyncResolveTypes = skeleton.asyncPromiseResolveReturnTypes
             if !asyncResolveTypes.isEmpty {
@@ -875,6 +884,63 @@ public class ExportSwift {
     }
 }
 
+// MARK: - GenericConformanceCodegen
+
+/// Renders `BridgedSwiftGenericBridgeable` conformances for `@JS` types so they
+/// can be used as the generic argument of a generic imported `@JSFunction`.
+struct GenericConformanceCodegen {
+    func renderConformance(typeName: String) -> [DeclSyntax] {
+        let printer = CodeFragmentPrinter()
+        printer.write("extension \(typeName): BridgedSwiftGenericBridgeable {")
+        printer.indent {
+            printer.write(
+                "@_spi(BridgeJS) public static let bridgeJSTypeHandle = \(typeName).bridgeJSMakeTypeHandle()"
+            )
+        }
+        printer.write("}")
+        return ["\(raw: printer.lines.joined(separator: "\n"))"]
+    }
+}
+
+// MARK: - GenericTypeRegistrationCodegen
+
+/// Renders the `bjs_<Module>_register_type_handles` wasm export: it lowers each
+/// registered type's `bridgeJSTypeID` into a buffer, in the canonical order of
+/// `BridgeJSSkeleton.typeRegistrationEntries`, and passes it to the JS import
+/// hook of the same name, which pairs the IDs with its codec array by index.
+public struct GenericTypeRegistrationCodegen {
+    public init() {}
+
+    public func render(for skeleton: BridgeJSSkeleton) -> String? {
+        guard let entries = skeleton.typeRegistrationEntries else { return nil }
+        let abiName = ABINameGenerator.typeRegistrationFunctionName(moduleName: skeleton.moduleName)
+        let printer = CodeFragmentPrinter()
+        printer.write("#if arch(wasm32)")
+        printer.write("@_extern(wasm, module: \"bjs\", name: \"\(abiName)\")")
+        printer.write("fileprivate func _\(abiName)_extern(_ base: UnsafePointer<Int32>?, _ count: Int32)")
+        printer.nextLine()
+        printer.write("@_expose(wasm, \"\(abiName)\")")
+        printer.write("public func _\(abiName)() {")
+        printer.indent {
+            printer.write("let typeIds: [Int32] = [")
+            printer.indent {
+                for entry in entries {
+                    printer.write("\(entry.swiftName).bridgeJSTypeID,")
+                }
+            }
+            printer.write("]")
+            printer.write("typeIds.withUnsafeBufferPointer { buffer in")
+            printer.indent {
+                printer.write("_\(abiName)_extern(buffer.baseAddress, Int32(buffer.count))")
+            }
+            printer.write("}")
+        }
+        printer.write("}")
+        printer.write("#endif")
+        return printer.lines.joined(separator: "\n")
+    }
+}
+
 // MARK: - StackCodegen
 
 /// Helper for stack-based lifting and lowering operations.
@@ -896,6 +962,10 @@ struct StackCodegen {
             return "JSObject.bridgeJSStackPop()"
         case .void, .namespaceEnum:
             return "()"
+        case .generic:
+            fatalError(
+                "Generic parameters are only supported on imported declarations, not exported concrete-type codegen"
+            )
         }
     }
 
@@ -908,7 +978,7 @@ struct StackCodegen {
             return "\(raw: typeName)<\(raw: wrappedType.swiftType)>.bridgeJSStackPop()"
         case .jsObject(let className?):
             return "\(raw: typeName)<JSObject>.bridgeJSStackPop().map { \(raw: className)(unsafelyWrapping: $0) }"
-        case .nullable, .void, .namespaceEnum, .closure, .unsafePointer, .swiftProtocol:
+        case .nullable, .void, .namespaceEnum, .closure, .unsafePointer, .swiftProtocol, .generic:
             fatalError("Invalid nullable wrapped type: \(wrappedType)")
         }
     }
@@ -941,6 +1011,10 @@ struct StackCodegen {
             return lowerArrayStatements(elementType: elementType, accessor: accessor, varPrefix: varPrefix)
         case .dictionary(let valueType):
             return lowerDictionaryStatements(valueType: valueType, accessor: accessor, varPrefix: varPrefix)
+        case .generic:
+            fatalError(
+                "Generic parameters are only supported on imported declarations, not exported concrete-type codegen"
+            )
         }
     }
 
@@ -1596,12 +1670,34 @@ extension BridgeType {
         case .associatedValueEnum:
             return ["_BridgedSwiftAssociatedValueEnum"]
         case .rawValueEnum, .void, .unsafePointer, .namespaceEnum,
-            .swiftProtocol, .closure, .nullable, .array, .dictionary, .alias:
+            .swiftProtocol, .closure, .nullable, .array, .dictionary, .alias, .generic:
             // Not supported yet.
             return nil
         }
     }
 
+    /// Stack expressions for bare `T` and `T?`, the only generic shapes that
+    /// cannot reuse the concrete emission: `bridgeJSLowerParameter()` names
+    /// per-type members that the generic constraint erases to the stack, so
+    /// `bridgeJSStackPush()`/`bridgeJSStackPop()` is the shared spelling.
+    /// `[T]` and `[String: T]` go through the ordinary paths via the `Array`
+    /// and `Dictionary` stack conformances.
+    var genericStackPopExpression: String? {
+        switch self {
+        case .generic(let name): return "\(name).bridgeJSStackPop()"
+        case .nullable(.generic(let name), _): return "Optional<\(name)>.bridgeJSStackPop()"
+        default: return nil
+        }
+    }
+
+    func genericStackPushStatement(value: String) -> String? {
+        switch self {
+        case .generic, .nullable(.generic, _):
+            return "\(value).bridgeJSStackPush()"
+        default: return nil
+        }
+    }
+
     var swiftType: String {
         switch self {
         case .bool: return "Bool"
@@ -1631,6 +1727,7 @@ extension BridgeType {
             let closureType = "(\(paramTypes))\(effectsStr) -> \(signature.returnType.swiftType)"
             return useJSTypedClosure ? "JSTypedClosure<\(closureType)>" : closureType
         case .alias(let name, _): return name
+        case .generic(let name): return name
         }
     }
 
@@ -1717,6 +1814,10 @@ extension BridgeType {
             return LiftingIntrinsicInfo(parameters: [])
         case .alias(_, let underlying):
             return try underlying.liftParameterInfo()
+        case .generic:
+            throw BridgeJSCoreError(
+                "Generic parameters are only supported on imported declarations, not exported concrete-type codegen"
+            )
         }
     }
 
@@ -1770,6 +1871,10 @@ extension BridgeType {
             return .array
         case .alias(_, let underlying):
             return try underlying.loweringReturnInfo()
+        case .generic:
+            throw BridgeJSCoreError(
+                "Generic parameters are only supported on imported declarations, not exported concrete-type codegen"
+            )
         }
     }
 }