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BridgeJS: Fix JSValue reference ownership across the bridge #31

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b8003b8
BridgeJS: Diagnose async and throwing @JS struct initializers
krodak Nov 3, 2026
0d41cbf
Merge pull request #825 from PassiveLogic/kr/bridgejs-throwing-struct…
krodak Nov 3, 2026
f1d5c94
BridgeJS: Fix JSValue reference ownership across the bridge
krodak Nov 3, 2026
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8 changes: 8 additions & 0 deletions Plugins/BridgeJS/Sources/BridgeJSCore/SwiftToSkeleton.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -1986,6 +1986,14 @@ private final class ExportSwiftAPICollector: SyntaxAnyVisitor {
guard let effects = collectEffects(signature: node.signature) else {
return .skipChildren
}
if effects.isAsync || effects.isThrows {
diagnose(
node: node,
message: "@JS struct initializer cannot be async or throw",
hint: "BridgeJS calls this initializer to rebuild struct values passed from JavaScript"
)
return .skipChildren
}

let structAbiName = exportedStructByName[structKey]?.abiName ?? "unknown"
let constructor = ExportedConstructor(
Expand Down
124 changes: 64 additions & 60 deletions Plugins/BridgeJS/Sources/BridgeJSLink/JSGlueGen.swift
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Expand Up @@ -749,6 +749,27 @@ struct IntrinsicJSFragment: Sendable {

private static let jsValueLowerHelperName = "__bjs_jsValueLower"
private static let jsValueLiftHelperName = "__bjs_jsValueLift"
private static let jsValueTakeHelperName = "__bjs_jsValueTake"

/// Mirrors `JavaScriptValueKind` in `_CJavaScriptKit.h`.
private enum JSValueKind: Int, CaseIterable {
case boolean = 0
case string = 1
case number = 2
case object = 3
case null = 4
case undefined = 5
case symbol = 7
case bigInt = 8

/// Whether `payload1` is a reference in `swift.memory`.
var holdsReference: Bool {
switch self {
case .string, .object, .symbol, .bigInt: return true
case .boolean, .number, .null, .undefined: return false
}
}
}

private static func registerJSValueHelpers(scope: JSGlueVariableScope) {
scope.registerIntrinsic("jsValueHelpers") { helperPrinter in
Expand Down Expand Up @@ -777,6 +798,20 @@ struct IntrinsicJSFragment: Sendable {
helperPrinter.write("return \(resultVar);")
}
helperPrinter.write("}")
helperPrinter.write("function \(jsValueTakeHelperName)(kind, payload1, payload2) {")
helperPrinter.indent {
helperPrinter.write("const value = \(jsValueLiftHelperName)(kind, payload1, payload2);")
let holdsReference = JSValueKind.allCases.filter(\.holdsReference)
.map { "kind === \($0.rawValue)" }
.joined(separator: " || ")
helperPrinter.write("if (\(holdsReference)) {")
helperPrinter.indent {
helperPrinter.write("\(JSGlueVariableScope.reservedSwift).memory.release(payload1);")
}
helperPrinter.write("}")
helperPrinter.write("return value;")
}
helperPrinter.write("}")
}
}

Expand All @@ -792,7 +827,7 @@ struct IntrinsicJSFragment: Sendable {
printer.write("let \(payload2Var);")
printer.write("if (\(value) === null) {")
printer.indent {
printer.write("\(kindVar) = 4;")
printer.write("\(kindVar) = \(JSValueKind.null.rawValue);")
printer.write("\(payload1Var) = 0;")
printer.write("\(payload2Var) = 0;")
}
Expand All @@ -802,41 +837,41 @@ struct IntrinsicJSFragment: Sendable {
printer.indent {
printer.write("case \"boolean\":")
printer.indent {
printer.write("\(kindVar) = 0;")
printer.write("\(kindVar) = \(JSValueKind.boolean.rawValue);")
printer.write("\(payload1Var) = \(value) ? 1 : 0;")
printer.write("\(payload2Var) = 0;")
printer.write("break;")
}
printer.write("case \"number\":")
printer.indent {
printer.write("\(kindVar) = 2;")
printer.write("\(kindVar) = \(JSValueKind.number.rawValue);")
printer.write("\(payload1Var) = 0;")
printer.write("\(payload2Var) = \(value);")
printer.write("break;")
}
func emitRetainCase(_ caseName: String, kind: Int) {
func emitRetainCase(_ caseName: String, kind: JSValueKind) {
printer.write("case \"\(caseName)\":")
printer.indent {
printer.write("\(kindVar) = \(kind);")
printer.write("\(kindVar) = \(kind.rawValue);")
printer.write(
"\(payload1Var) = \(JSGlueVariableScope.reservedSwift).memory.retain(\(value));"
)
printer.write("\(payload2Var) = 0;")
printer.write("break;")
}
}
emitRetainCase("string", kind: 1)
emitRetainCase("string", kind: .string)
printer.write("case \"undefined\":")
printer.indent {
printer.write("\(kindVar) = 5;")
printer.write("\(kindVar) = \(JSValueKind.undefined.rawValue);")
printer.write("\(payload1Var) = 0;")
printer.write("\(payload2Var) = 0;")
printer.write("break;")
}
emitRetainCase("object", kind: 3)
emitRetainCase("function", kind: 3)
emitRetainCase("symbol", kind: 7)
emitRetainCase("bigint", kind: 8)
emitRetainCase("object", kind: .object)
emitRetainCase("function", kind: .object)
emitRetainCase("symbol", kind: .symbol)
emitRetainCase("bigint", kind: .bigInt)
printer.write("default:")
printer.indent {
printer.write("throw new TypeError(\"Unsupported JSValue type\");")
Expand Down Expand Up @@ -874,53 +909,21 @@ struct IntrinsicJSFragment: Sendable {
printer.write("let \(resultVar);")
printer.write("switch (\(kind)) {")
printer.indent {
printer.write("case 0:")
printer.indent {
printer.write("\(resultVar) = \(payload1) !== 0;")
printer.write("break;")
}
printer.write("case 1:")
printer.indent {
printer.write(
"\(resultVar) = \(JSGlueVariableScope.reservedSwift).memory.getObject(\(payload1));"
)
printer.write("break;")
}
printer.write("case 2:")
printer.indent {
printer.write("\(resultVar) = \(payload2);")
printer.write("break;")
}
printer.write("case 3:")
printer.indent {
printer.write(
"\(resultVar) = \(JSGlueVariableScope.reservedSwift).memory.getObject(\(payload1));"
)
printer.write("break;")
}
printer.write("case 4:")
printer.indent {
printer.write("\(resultVar) = null;")
printer.write("break;")
}
printer.write("case 5:")
printer.indent {
printer.write("\(resultVar) = undefined;")
printer.write("break;")
}
printer.write("case 7:")
printer.indent {
printer.write(
"\(resultVar) = \(JSGlueVariableScope.reservedSwift).memory.getObject(\(payload1));"
)
printer.write("break;")
}
printer.write("case 8:")
printer.indent {
printer.write(
"\(resultVar) = \(JSGlueVariableScope.reservedSwift).memory.getObject(\(payload1));"
)
printer.write("break;")
for valueKind in JSValueKind.allCases {
let value: String
switch valueKind {
case .boolean: value = "\(payload1) !== 0"
case .number: value = payload2
case .null: value = "null"
case .undefined: value = "undefined"
case .string, .object, .symbol, .bigInt:
value = "\(JSGlueVariableScope.reservedSwift).memory.getObject(\(payload1))"
}
printer.write("case \(valueKind.rawValue):")
printer.indent {
printer.write("\(resultVar) = \(value);")
printer.write("break;")
}
}
printer.write("default:")
printer.indent {
Expand Down Expand Up @@ -961,11 +964,12 @@ struct IntrinsicJSFragment: Sendable {
let resultVar = scope.variable("jsValue")
registerJSValueHelpers(scope: scope)
printer.write(
"const \(resultVar) = \(jsValueLiftHelperName)(\(kind), \(payload1), \(payload2));"
"const \(resultVar) = \(jsValueTakeHelperName)(\(kind), \(payload1), \(payload2));"
)
return [resultVar]
}
)
/// Swift lends the payload reference for the duration of the call, so it is not released here.
static let jsValueLiftParameter = IntrinsicJSFragment(
parameters: ["kind", "payload1", "payload2"],
printCode: { arguments, context in
Expand Down Expand Up @@ -2232,7 +2236,7 @@ struct IntrinsicJSFragment: Sendable {
let resultVar = scope.variable("jsValue")
registerJSValueHelpers(scope: scope)
printer.write(
"const \(resultVar) = \(jsValueLiftHelperName)(\(kindVar), \(payload1Var), \(payload2Var));"
"const \(resultVar) = \(jsValueTakeHelperName)(\(kindVar), \(payload1Var), \(payload2Var));"
)
return [resultVar]
}
Expand Down
15 changes: 15 additions & 0 deletions Plugins/BridgeJS/Tests/BridgeJSToolTests/DiagnosticsTests.swift
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Expand Up @@ -535,6 +535,21 @@ import Testing
#expect(skeleton.exported != nil)
}

@Test
func throwingStructInitProducesDiagnostic() throws {
let source = """
@JS struct Point {
var x: Double

@JS init(x: Double) throws(JSException) {
self.x = x
}
}
"""
let diagnostics = try #require(moduleDiagnostics(source: source))
#expect(diagnostics.description.contains("@JS struct initializer cannot be async or throw"))
}

@Test
func structWithoutExplicitInitSucceeds() throws {
let source = """
Expand Down
9 changes: 8 additions & 1 deletion Plugins/BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/BridgeJSLinkTests/Alias.js
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Expand Up @@ -267,7 +267,7 @@ export async function createInstantiator(options, swift) {
const jsValuePayload2 = f64Stack.pop();
const jsValuePayload1 = i32Stack.pop();
const jsValueKind = i32Stack.pop();
const jsValue = __bjs_jsValueLift(jsValueKind, jsValuePayload1, jsValuePayload2);
const jsValue = __bjs_jsValueTake(jsValueKind, jsValuePayload1, jsValuePayload2);
return jsValue;
},
},
Expand Down Expand Up @@ -361,6 +361,13 @@ export async function createInstantiator(options, swift) {
}
return jsValue;
}
function __bjs_jsValueTake(kind, payload1, payload2) {
const value = __bjs_jsValueLift(kind, payload1, payload2);
if (kind === 1 || kind === 3 || kind === 7 || kind === 8) {
swift.memory.release(payload1);
}
return value;
}

const __bjs_codec_M10TestModuleT16PolygonReference = {
lower: (v) => {
Expand Down
9 changes: 8 additions & 1 deletion Plugins/BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/BridgeJSLinkTests/ArrayTypes.js
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Expand Up @@ -274,7 +274,7 @@ export async function createInstantiator(options, swift) {
const jsValuePayload2 = f64Stack.pop();
const jsValuePayload1 = i32Stack.pop();
const jsValueKind = i32Stack.pop();
const jsValue = __bjs_jsValueLift(jsValueKind, jsValuePayload1, jsValuePayload2);
const jsValue = __bjs_jsValueTake(jsValueKind, jsValuePayload1, jsValuePayload2);
return jsValue;
},
},
Expand Down Expand Up @@ -368,6 +368,13 @@ export async function createInstantiator(options, swift) {
}
return jsValue;
}
function __bjs_jsValueTake(kind, payload1, payload2) {
const value = __bjs_jsValueLift(kind, payload1, payload2);
if (kind === 1 || kind === 3 || kind === 7 || kind === 8) {
swift.memory.release(payload1);
}
return value;
}

const __bjs_codec_Array_Int = __bjs_arrayCodec(__bjs_primitiveCodecs.Int);
const __bjs_codec_Array_String = __bjs_arrayCodec(__bjs_stringCodec);
Expand Down
9 changes: 8 additions & 1 deletion Plugins/BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/BridgeJSLinkTests/Async.js
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Expand Up @@ -271,7 +271,7 @@ export async function createInstantiator(options, swift) {
const jsValuePayload2 = f64Stack.pop();
const jsValuePayload1 = i32Stack.pop();
const jsValueKind = i32Stack.pop();
const jsValue = __bjs_jsValueLift(jsValueKind, jsValuePayload1, jsValuePayload2);
const jsValue = __bjs_jsValueTake(jsValueKind, jsValuePayload1, jsValuePayload2);
return jsValue;
},
},
Expand Down Expand Up @@ -365,6 +365,13 @@ export async function createInstantiator(options, swift) {
}
return jsValue;
}
function __bjs_jsValueTake(kind, payload1, payload2) {
const value = __bjs_jsValueLift(kind, payload1, payload2);
if (kind === 1 || kind === 3 || kind === 7 || kind === 8) {
swift.memory.release(payload1);
}
return value;
}

const __bjs_codec_M10TestModuleT10AsyncPoint = {
lower: (v) => {
Expand Down
7 changes: 7 additions & 0 deletions ...dgeJS/Tests/BridgeJSToolTests/__Snapshots__/BridgeJSLinkTests/AsyncAssociatedValueEnum.js
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Expand Up @@ -128,6 +128,13 @@ export async function createInstantiator(options, swift) {
}
return jsValue;
}
function __bjs_jsValueTake(kind, payload1, payload2) {
const value = __bjs_jsValueLift(kind, payload1, payload2);
if (kind === 1 || kind === 3 || kind === 7 || kind === 8) {
swift.memory.release(payload1);
}
return value;
}

const __bjs_createEnumHelpers_M10TestModuleT18AsyncPayloadResult = () => ({
lower: (value) => {
Expand Down
7 changes: 7 additions & 0 deletions Plugins/BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/BridgeJSLinkTests/AsyncImport.js
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Expand Up @@ -121,6 +121,13 @@ export async function createInstantiator(options, swift) {
}
return jsValue;
}
function __bjs_jsValueTake(kind, payload1, payload2) {
const value = __bjs_jsValueLift(kind, payload1, payload2);
if (kind === 1 || kind === 3 || kind === 7 || kind === 8) {
swift.memory.release(payload1);
}
return value;
}

const swiftClosureRegistry = (typeof FinalizationRegistry === "undefined") ? { register: () => {}, unregister: () => {} } : new FinalizationRegistry((state) => {
if (state.unregistered) { return; }
Expand Down
7 changes: 7 additions & 0 deletions ...ins/BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/BridgeJSLinkTests/AsyncStaticImport.js
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Expand Up @@ -121,6 +121,13 @@ export async function createInstantiator(options, swift) {
}
return jsValue;
}
function __bjs_jsValueTake(kind, payload1, payload2) {
const value = __bjs_jsValueLift(kind, payload1, payload2);
if (kind === 1 || kind === 3 || kind === 7 || kind === 8) {
swift.memory.release(payload1);
}
return value;
}

const swiftClosureRegistry = (typeof FinalizationRegistry === "undefined") ? { register: () => {}, unregister: () => {} } : new FinalizationRegistry((state) => {
if (state.unregistered) { return; }
Expand Down
9 changes: 8 additions & 1 deletion ...ins/BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/BridgeJSLinkTests/DefaultParameters.js
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Expand Up @@ -267,7 +267,7 @@ export async function createInstantiator(options, swift) {
const jsValuePayload2 = f64Stack.pop();
const jsValuePayload1 = i32Stack.pop();
const jsValueKind = i32Stack.pop();
const jsValue = __bjs_jsValueLift(jsValueKind, jsValuePayload1, jsValuePayload2);
const jsValue = __bjs_jsValueTake(jsValueKind, jsValuePayload1, jsValuePayload2);
return jsValue;
},
},
Expand Down Expand Up @@ -361,6 +361,13 @@ export async function createInstantiator(options, swift) {
}
return jsValue;
}
function __bjs_jsValueTake(kind, payload1, payload2) {
const value = __bjs_jsValueLift(kind, payload1, payload2);
if (kind === 1 || kind === 3 || kind === 7 || kind === 8) {
swift.memory.release(payload1);
}
return value;
}

const __bjs_codec_M10TestModuleT6Config = {
lower: (v) => {
Expand Down
9 changes: 8 additions & 1 deletion Plugins/BridgeJS/Tests/BridgeJSToolTests/__Snapshots__/BridgeJSLinkTests/DictionaryTypes.js
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Expand Up @@ -261,7 +261,7 @@ export async function createInstantiator(options, swift) {
const jsValuePayload2 = f64Stack.pop();
const jsValuePayload1 = i32Stack.pop();
const jsValueKind = i32Stack.pop();
const jsValue = __bjs_jsValueLift(jsValueKind, jsValuePayload1, jsValuePayload2);
const jsValue = __bjs_jsValueTake(jsValueKind, jsValuePayload1, jsValuePayload2);
return jsValue;
},
},
Expand Down Expand Up @@ -355,6 +355,13 @@ export async function createInstantiator(options, swift) {
}
return jsValue;
}
function __bjs_jsValueTake(kind, payload1, payload2) {
const value = __bjs_jsValueLift(kind, payload1, payload2);
if (kind === 1 || kind === 3 || kind === 7 || kind === 8) {
swift.memory.release(payload1);
}
return value;
}

const __bjs_codec_Dict_Int = __bjs_dictCodec(__bjs_primitiveCodecs.Int);
const __bjs_codec_Dict_String = __bjs_dictCodec(__bjs_stringCodec);
Expand Down
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