BridgeJS: Use a BigInt zero placeholder for Wasm i64 in generated JS

A Wasm i64 parameter or return value is represented as a JavaScript BigInt.
The generated JS used a plain 0 as the placeholder for the absent case of an
optional i64 parameter (isSome ? v : 0) and for the error-path return of an
imported thunk, so calling such an export with null (or an imported i64
function throwing) raised "TypeError: Cannot convert 0 to a BigInt".

Emit 0n for i64 in both placeholders (jsZeroLiteral and the imported-thunk
return placeholder). This was latent because the optional Int64/UInt64
round-trip tests never exercised the none case; add those assertions.

Author: krodak

Plugins/BridgeJS/Sources/BridgeJSLink/BridgeJSLink.swift

@@ -3704,7 +3704,10 @@ extension BridgeType {
 extension WasmCoreType {
     fileprivate var placeholderValue: String {
         switch self {
-        case .i32, .i64, .f32, .f64, .pointer: return "0"
+        // A Wasm `i64` return is a JavaScript `BigInt`, so the error-path placeholder
+        // must be a BigInt literal rather than a plain number.
+        case .i64: return "0n"
+        case .i32, .f32, .f64, .pointer: return "0"
         }
     }
 }

Plugins/BridgeJS/Sources/BridgeJSLink/JSGlueGen.swift

@@ -2603,7 +2603,10 @@ fileprivate extension WasmCoreType {
     var jsZeroLiteral: String {
         switch self {
         case .f32, .f64: return "0.0"
-        case .i32, .i64, .pointer: return "0"
+        // A Wasm `i64` parameter is passed as a JavaScript `BigInt`, so its zero
+        // placeholder must be a BigInt literal rather than a plain number.
+        case .i64: return "0n"
+        case .i32, .pointer: return "0"
         }
     }
 }

Plugins/BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/BridgeJSLinkTests/EnumRawType.js

@@ -440,7 +440,7 @@ export async function createInstantiator(options, swift) {
                 },
                 roundTripOptionalFileSize: function bjs_roundTripOptionalFileSize(input) {
                     const isSome = input != null;
-                    instance.exports.bjs_roundTripOptionalFileSize(+isSome, isSome ? input : 0);
+                    instance.exports.bjs_roundTripOptionalFileSize(+isSome, isSome ? input : 0n);
                     const isSome1 = i32Stack.pop();
                     let optResult;
                     if (isSome1) {
@@ -488,7 +488,7 @@ export async function createInstantiator(options, swift) {
                 },
                 roundTripOptionalSessionId: function bjs_roundTripOptionalSessionId(input) {
                     const isSome = input != null;
-                    instance.exports.bjs_roundTripOptionalSessionId(+isSome, isSome ? input : 0);
+                    instance.exports.bjs_roundTripOptionalSessionId(+isSome, isSome ? input : 0n);
                     const isSome1 = i32Stack.pop();
                     let optResult;
                     if (isSome1) {

Plugins/BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/BridgeJSLinkTests/FixedWidthIntegers.js

@@ -258,7 +258,7 @@ export async function createInstantiator(options, swift) {
                     return ret;
                 } catch (error) {
                     setException(error);
-                    return 0
+                    return 0n
                 }
             }
             TestModule["bjs_roundTripUInt64"] = function bjs_roundTripUInt64(v) {
@@ -267,7 +267,7 @@ export async function createInstantiator(options, swift) {
                     return ret;
                 } catch (error) {
                     setException(error);
-                    return 0
+                    return 0n
                 }
             }
         },

Tests/BridgeJSRuntimeTests/JavaScript/OptionalSupportTests.mjs

@@ -80,6 +80,10 @@ export function runJsOptionalSupportTests(rootExports) {
     assert.equal(exports.roundTripOptionalIntRawValueEnum(HttpStatus.Ok), HttpStatusValues.Ok);
     assert.equal(exports.roundTripOptionalInt64RawValueEnum(FileSize.Tiny), FileSizeValues.Tiny);
     assert.equal(exports.roundTripOptionalUInt64RawValueEnum(SessionId.Active), SessionIdValues.Active);
+    // The `none` case lowers the i64/u64 placeholder as a BigInt (`0n`); a plain `0`
+    // would throw "Cannot convert 0 to a BigInt" when calling the Wasm export.
+    assert.equal(exports.roundTripOptionalInt64RawValueEnum(null), null);
+    assert.equal(exports.roundTripOptionalUInt64RawValueEnum(null), null);
     assert.equal(exports.roundTripOptionalTSEnum(TSDirection.North), TSDirection.North);
     assert.equal(exports.roundTripOptionalTSStringEnum(TSTheme.Light), TSTheme.Light);
     assert.equal(exports.roundTripOptionalNamespacedEnum(Networking.API.Method.Get), Networking.API.Method.Get);