BridgeJS: Exercise generic imports under Embedded Swift

krodak · krodak · commit b5fe11b98122 · 2026-07-14T16:29:06.000+02:00
diff --git a/Examples/Embedded/Package.swift b/Examples/Embedded/Package.swift
@@ -16,6 +16,9 @@ let package = Package(
             swiftSettings: [
                 .enableExperimentalFeature("Extern")
             ],
+            plugins: [
+                .plugin(name: "BridgeJS", package: "JavaScriptKit")
+            ]
         )
     ],
     swiftLanguageModes: [.v5]
diff --git a/Examples/Embedded/Sources/EmbeddedApp/main.swift b/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)
 }
diff --git a/Examples/Embedded/index.html b/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>
 
diff --git a/Sources/JavaScriptKit/Documentation.docc/Articles/BridgeJS/BridgeJS-Internals/Design-Rationale.md b/Sources/JavaScriptKit/Documentation.docc/Articles/BridgeJS/BridgeJS-Internals/Design-Rationale.md
@@ -34,7 +34,7 @@ BridgeJS avoids this by generating **separate** access paths per property or met
 
 ## Generic imports
 
-An imported generic `@JSFunction` (`func parse<T: BridgedSwiftGenericBridgeable>(...)`) lets one piece of glue serve many concrete types. The generic value crosses using the type's own stack ABI, and a runtime type ID (interned once via `swift_js_resolve_type_id`) selects the matching JS codec, so the type-agnostic glue can lower and lift the right representation without a specialized path per call site.
+An imported generic `@JSFunction` (`func parse<T: BridgedSwiftGenericBridgeable>(...)`) lets one piece of glue serve many concrete types. The generic value crosses using the type's own stack ABI, and a runtime type ID (interned once via `swift_js_resolve_type_id`) selects the matching JS codec, so the type-agnostic glue can lower and lift the right representation without a specialized path per call site. Because this path avoids existentials entirely, it also works under Embedded Swift; the Embedded example (`Examples/Embedded`) exercises a generic import, including a `@JS struct` round-trip.
 
 ## Generic exports
 
diff --git a/Sources/JavaScriptKit/Documentation.docc/Articles/BridgeJS/Unsupported-Features.md b/Sources/JavaScriptKit/Documentation.docc/Articles/BridgeJS/Unsupported-Features.md
@@ -49,4 +49,4 @@ The generic parameter may be used bare (`T`) or wrapped in `[T]`, `T?`, or `[Str
 
 The generic argument must be a primitive or a type defined in the same module as the generic function. Using a `@JS` type from another module as the generic argument is not supported yet: at an imported `@JSFunction` call site this surfaces as a Swift conformance error, and an exported `@JS` function traps at runtime when passed such a type's token.
 
-Exported generic functions additionally require runtime existential support, so they are not available under Embedded Swift. Imported generics remain available there.
+Exported generic functions additionally require runtime existential support, so they are not available under Embedded Swift. Imported generics remain available there and are exercised by the Embedded example (`Examples/Embedded`).

Original file line number	Diff line number	Diff line change
@@ -49,4 +49,4 @@ The generic parameter may be used bare (`T`) or wrapped in `[T]`, `T?`, or `[Str
`49`	`49`
`50`	`50`	The generic argument must be a primitive or a type defined in the same module as the generic function. Using a `@JS` type from another module as the generic argument is not supported yet: at an imported `@JSFunction` call site this surfaces as a Swift conformance error, and an exported `@JS` function traps at runtime when passed such a type's token.
`51`	`51`
`52`		`-Exported generic functions additionally require runtime existential support, so they are not available under Embedded Swift. Imported generics remain available there.`
	`52`	+Exported generic functions additionally require runtime existential support, so they are not available under Embedded Swift. Imported generics remain available there and are exercised by the Embedded example (`Examples/Embedded`).