Added JS null/undefined optional coverage and strict TS config for generation:

- Created `tsconfig.json` with strict/null-checking to ensure unions survive into BridgeJS generation.
- Extended runtime JS prelude and `bridge-js.d.ts` with optional number round-trips, regenerated bindings via `Utilities/bridge-js-generate.sh`, and added Swift runtime tests in `Tests/BridgeJSRuntimeTests/ImportAPITests.swift` to exercise `T | null` → `Optional` and `T | undefined` → `JSUndefinedOr`.
- Regenerated BridgeJS runtime artifacts under `Tests/BridgeJSRuntimeTests/Generated/` and related outputs.

Tests executed:
- `swift test --package-path ./Plugins/BridgeJS`
- `SWIFT_SDK_ID=DEVELOPMENT-SNAPSHOT-2025-11-03-a-wasm32-unknown-wasip1 make unittest`

Author: kateinoigakukun

Tests/BridgeJSRuntimeTests/Generated/BridgeJS.Macros.swift

@@ -14,6 +14,10 @@
 
 @JSFunction func jsRoundTripString(_ v: String) throws (JSException) -> String
 
+@JSFunction func jsRoundTripOptionalNumberNull(_ v: Optional<Double>) throws (JSException) -> Optional<Double>
+
+@JSFunction func jsRoundTripOptionalNumberUndefined(_ v: JSUndefinedOr<Double>) throws (JSException) -> JSUndefinedOr<Double>
+
 @JSFunction func jsThrowOrVoid(_ shouldThrow: Bool) throws (JSException) -> Void
 
 @JSFunction func jsThrowOrNumber(_ shouldThrow: Bool) throws (JSException) -> Double

Tests/BridgeJSRuntimeTests/Generated/BridgeJS.swift

@@ -7648,6 +7648,42 @@ func _$jsRoundTripString(_ v: String) throws(JSException) -> String {
     return String.bridgeJSLiftReturn(ret)
 }
 
+#if arch(wasm32)
+@_extern(wasm, module: "BridgeJSRuntimeTests", name: "bjs_jsRoundTripOptionalNumberNull")
+fileprivate func bjs_jsRoundTripOptionalNumberNull(_ vIsSome: Int32, _ vValue: Float64) -> Void
+#else
+fileprivate func bjs_jsRoundTripOptionalNumberNull(_ vIsSome: Int32, _ vValue: Float64) -> Void {
+    fatalError("Only available on WebAssembly")
+}
+#endif
+
+func _$jsRoundTripOptionalNumberNull(_ v: Optional<Double>) throws(JSException) -> Optional<Double> {
+    let (vIsSome, vValue) = v.bridgeJSLowerParameter()
+    bjs_jsRoundTripOptionalNumberNull(vIsSome, vValue)
+    if let error = _swift_js_take_exception() {
+        throw error
+    }
+    return Optional<Double>.bridgeJSLiftReturnFromSideChannel()
+}
+
+#if arch(wasm32)
+@_extern(wasm, module: "BridgeJSRuntimeTests", name: "bjs_jsRoundTripOptionalNumberUndefined")
+fileprivate func bjs_jsRoundTripOptionalNumberUndefined(_ vIsDefined: Int32, _ vValue: Float64) -> Void
+#else
+fileprivate func bjs_jsRoundTripOptionalNumberUndefined(_ vIsDefined: Int32, _ vValue: Float64) -> Void {
+    fatalError("Only available on WebAssembly")
+}
+#endif
+
+func _$jsRoundTripOptionalNumberUndefined(_ v: JSUndefinedOr<Double>) throws(JSException) -> JSUndefinedOr<Double> {
+    let (vIsDefined, vValue) = v.bridgeJSLowerParameter()
+    bjs_jsRoundTripOptionalNumberUndefined(vIsDefined, vValue)
+    if let error = _swift_js_take_exception() {
+        throw error
+    }
+    return JSUndefinedOr<Double>.bridgeJSLiftReturnFromSideChannel()
+}
+
 #if arch(wasm32)
 @_extern(wasm, module: "BridgeJSRuntimeTests", name: "bjs_jsThrowOrVoid")
 fileprivate func bjs_jsThrowOrVoid(_ shouldThrow: Int32) -> Void

Tests/BridgeJSRuntimeTests/Generated/JavaScript/BridgeJS.json

@@ -11475,6 +11475,58 @@
               }
             }
           },
+          {
+            "name" : "jsRoundTripOptionalNumberNull",
+            "parameters" : [
+              {
+                "name" : "v",
+                "type" : {
+                  "optional" : {
+                    "_0" : {
+                      "double" : {
+
+                      }
+                    }
+                  }
+                }
+              }
+            ],
+            "returnType" : {
+              "optional" : {
+                "_0" : {
+                  "double" : {
+
+                  }
+                }
+              }
+            }
+          },
+          {
+            "name" : "jsRoundTripOptionalNumberUndefined",
+            "parameters" : [
+              {
+                "name" : "v",
+                "type" : {
+                  "undefinedOr" : {
+                    "_0" : {
+                      "double" : {
+
+                      }
+                    }
+                  }
+                }
+              }
+            ],
+            "returnType" : {
+              "undefinedOr" : {
+                "_0" : {
+                  "double" : {
+
+                  }
+                }
+              }
+            }
+          },
           {
             "name" : "jsThrowOrVoid",
             "parameters" : [

Tests/BridgeJSRuntimeTests/ImportAPITests.swift

@@ -35,6 +35,26 @@ class ImportAPITests: XCTestCase {
         }
     }
 
+    func testRoundTripOptionalNumberNull() throws {
+        try XCTAssertEqual(jsRoundTripOptionalNumberNull(42), 42)
+        try XCTAssertNil(jsRoundTripOptionalNumberNull(nil))
+    }
+
+    func testRoundTripOptionalNumberUndefined() throws {
+        let some = try jsRoundTripOptionalNumberUndefined(.value(42))
+        switch some {
+        case .value(let value):
+            XCTAssertEqual(value, 42)
+        case .undefined:
+            XCTFail("Expected defined value")
+        }
+
+        let undefined = try jsRoundTripOptionalNumberUndefined(.undefinedValue)
+        if case .value = undefined {
+            XCTFail("Expected undefined")
+        }
+    }
+
     func testRoundTripFeatureFlag() throws {
         for v in [FeatureFlag.foo, .bar] {
             try XCTAssertEqual(jsRoundTripFeatureFlag(v), v)

Tests/BridgeJSRuntimeTests/bridge-js.d.ts

@@ -2,6 +2,8 @@ export function jsRoundTripVoid(): void
 export function jsRoundTripNumber(v: number): number
 export function jsRoundTripBool(v: boolean): boolean
 export function jsRoundTripString(v: string): string
+export function jsRoundTripOptionalNumberNull(v: number | null): number | null
+export function jsRoundTripOptionalNumberUndefined(v: number | undefined): number | undefined
 export function jsThrowOrVoid(shouldThrow: boolean): void
 export function jsThrowOrNumber(shouldThrow: boolean): number
 export function jsThrowOrBool(shouldThrow: boolean): boolean

Tests/prelude.mjs

@@ -25,6 +25,12 @@ export async function setupOptions(options, context) {
                 "jsRoundTripString": (v) => {
                     return v;
                 },
+                "jsRoundTripOptionalNumberNull": (v) => {
+                    return v ?? null;
+                },
+                "jsRoundTripOptionalNumberUndefined": (v) => {
+                    return v === undefined ? undefined : v;
+                },
                 "jsThrowOrVoid": (shouldThrow) => {
                     if (shouldThrow) {
                         throw new Error("TestError");

tsconfig.json

@@ -0,0 +1,8 @@
+{
+  "compilerOptions": {
+    "strict": true,
+    "noEmit": true,
+    "lib": ["es2020", "DOM"],
+    "skipLibCheck": true
+  }
+}