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BridgeJS: Support throws and async for closures #11

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106 changes: 96 additions & 10 deletions Plugins/BridgeJS/Sources/BridgeJSCore/ClosureCodegen.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,7 @@ public struct ClosureCodegen {
let closureParams = signature.parameters.map { "\(sendingPrefix)\($0.closureSwiftType)" }.joined(
separator: ", "
)
let swiftEffects = (signature.isAsync ? " async" : "") + (signature.isThrows ? " throws" : "")
let swiftEffects = (signature.isAsync ? " async" : "") + (signature.isThrows ? " throws(JSException)" : "")
let swiftReturnType = signature.returnType.closureSwiftType
return "(\(closureParams))\(swiftEffects) -> \(swiftReturnType)"
}
Expand Down Expand Up @@ -73,7 +73,17 @@ public struct ClosureCodegen {
helperEnumDeclPrinter.indent {
helperEnumDeclPrinter.write("let callback = JSObject.bridgeJSLiftParameter(callbackId)")
let parameters: String
if signature.parameters.isEmpty {
if signature.isThrows || signature.isAsync {
let sendingPrefix = signature.sendingParameters ? "sending " : ""
let typedParams =
signature.parameters.enumerated().map { index, paramType in
"param\(index): \(sendingPrefix)\(paramType.closureSwiftType)"
}.joined(separator: ", ")
let returnType = signature.returnType.closureSwiftType
let effects =
(signature.isAsync ? " async" : "") + (signature.isThrows ? " throws(JSException)" : "")
parameters = " (\(typedParams))\(effects) -> \(returnType)"
} else if signature.parameters.isEmpty {
parameters = ""
} else if signature.parameters.count == 1 {
parameters = " param0"
Expand Down Expand Up @@ -146,22 +156,25 @@ public struct ClosureCodegen {
liftedParams.append("\(paramType.swiftType).bridgeJSLiftParameter(\(argNames.joined(separator: ", ")))")
}

let closureCallExpr = ExprSyntax("closure(\(raw: liftedParams.joined(separator: ", ")))")
let tryPrefix = signature.isThrows ? "try " : ""
let closureCallExpr = ExprSyntax("\(raw: tryPrefix)closure(\(raw: liftedParams.joined(separator: ", ")))")
let asyncTryPrefix = (signature.isThrows ? "try " : "") + "await "
let asyncClosureCallExpr = ExprSyntax(
"\(raw: asyncTryPrefix)closure(\(raw: liftedParams.joined(separator: ", ")))"
)

let abiReturnWasmType = try signature.returnType.loweringReturnInfo().returnType
let abiReturnWasmType =
signature.isAsync
? try BridgeType.jsObject(nil).loweringReturnInfo().returnType
: try signature.returnType.loweringReturnInfo().returnType

// Build signature using SwiftSignatureBuilder
let funcSignature = SwiftSignatureBuilder.buildABIFunctionSignature(
abiParameters: abiParams,
returnType: abiReturnWasmType
)

// Build function declaration using helper
let funcDecl = SwiftCodePattern.buildExposedFunctionDecl(
abiName: abiName,
signature: funcSignature
) { printer in
printer.write("let closure = Unmanaged<\(boxType)>.fromOpaque(boxPtr).takeUnretainedValue().closure")
let emitCallAndLower: (CodeFragmentPrinter) -> Void = { printer in
if signature.returnType == .void {
printer.write(closureCallExpr.description)
} else {
Expand Down Expand Up @@ -189,6 +202,79 @@ public struct ClosureCodegen {
}
}

let emitAsyncCallAndLower: (CodeFragmentPrinter) -> Void = { printer in
printer.write("let closure = Unmanaged<\(boxType)>.fromOpaque(boxPtr).takeUnretainedValue().closure")
let resolveType = signature.returnType
let resolveName = "Promise_resolve_\(resolveType.mangleTypeName)"
let rejectName = "Promise_reject"
let closureHead: String
if signature.isThrows {
let returnSpelling = resolveType == .void ? "" : " -> \(resolveType.closureSwiftType)"
closureHead = " () async throws(JSException)\(returnSpelling) in"
} else {
closureHead = ""
}
printer.write("return _bjs_makePromise(resolve: \(resolveName), reject: \(rejectName)) {\(closureHead)")
printer.indent {
if resolveType == .void {
printer.write(asyncClosureCallExpr.description)
} else {
printer.write("return \(asyncClosureCallExpr)")
}
}
printer.write("}")
}

let catchPlaceholderStmt = abiReturnWasmType?.swiftReturnPlaceholderStmt

// Build function declaration using helper
let funcDecl = SwiftCodePattern.buildExposedFunctionDecl(
abiName: abiName,
signature: funcSignature
) { printer in
if signature.isAsync {
emitAsyncCallAndLower(printer)
} else if signature.isThrows {
printer.write(
"let closure = Unmanaged<\(boxType)>.fromOpaque(boxPtr).takeUnretainedValue().closure"
)
printer.write("do {")
printer.indent {
emitCallAndLower(printer)
}
printer.write("} catch let error {")
printer.indent {
printer.write("if let error = error.thrownValue.object {")
printer.indent {
printer.write("withExtendedLifetime(error) {")
printer.indent {
printer.write("_swift_js_throw(Int32(bitPattern: $0.id))")
}
printer.write("}")
}
printer.write("} else {")
printer.indent {
printer.write("let jsError = JSError(message: error.description)")
printer.write("withExtendedLifetime(jsError.jsObject) {")
printer.indent {
printer.write("_swift_js_throw(Int32(bitPattern: $0.id))")
}
printer.write("}")
}
printer.write("}")
if let catchPlaceholderStmt {
printer.write(catchPlaceholderStmt)
}
}
printer.write("}")
} else {
printer.write(
"let closure = Unmanaged<\(boxType)>.fromOpaque(boxPtr).takeUnretainedValue().closure"
)
emitCallAndLower(printer)
}
}

return DeclSyntax(funcDecl)
}

Expand Down
9 changes: 4 additions & 5 deletions Plugins/BridgeJS/Sources/BridgeJSCore/ImportTS.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -272,9 +272,7 @@ public struct ImportTS {
}
}

// Add exception check for ImportTS context (skipped for async, where
// errors are funneled through the JS-side reject path)
if !effects.isAsync && context == .importTS {
if !effects.isAsync && (context == .importTS || effects.isThrows) {
body.write("if let error = _swift_js_take_exception() { throw error }")
}
}
Expand Down Expand Up @@ -323,18 +321,19 @@ public struct ImportTS {
let innerBody = body
body = CodeFragmentPrinter()

let tryKeyword = effects.isThrows ? "try" : "try!"
let rejectFactory = "makeRejectClosure: { JSTypedClosure<(sending JSValue) -> Void>($0) }"
if returnType == .void {
let resolveFactory = "makeResolveClosure: { JSTypedClosure<() -> Void>($0) }"
body.write(
"try await _bjs_awaitPromise(\(resolveFactory), \(rejectFactory)) { resolveRef, rejectRef in"
"\(tryKeyword) await _bjs_awaitPromise(\(resolveFactory), \(rejectFactory)) { resolveRef, rejectRef in"
)
} else {
let resolveSwiftType = returnType.closureSwiftType
let resolveFactory =
"makeResolveClosure: { JSTypedClosure<(sending \(resolveSwiftType)) -> Void>($0) }"
body.write(
"let resolved = try await _bjs_awaitPromise(\(resolveFactory), \(rejectFactory)) { resolveRef, rejectRef in"
"let resolved = \(tryKeyword) await _bjs_awaitPromise(\(resolveFactory), \(rejectFactory)) { resolveRef, rejectRef in"
)
}
body.indent {
Expand Down
20 changes: 15 additions & 5 deletions Plugins/BridgeJS/Sources/BridgeJSCore/Misc.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -137,14 +137,21 @@ import SwiftSyntax
import class Foundation.ProcessInfo

public struct DiagnosticError: Error {
public enum Severity: String, Sendable {
case error
case warning
}

public let node: Syntax
public let message: String
public let hint: String?
public let severity: Severity

public init(node: some SyntaxProtocol, message: String, hint: String? = nil) {
public init(node: some SyntaxProtocol, message: String, hint: String? = nil, severity: Severity = .error) {
self.node = Syntax(node)
self.message = message
self.hint = hint
self.severity = severity
}

/// Formats the diagnostic error as a string.
Expand All @@ -166,12 +173,14 @@ public struct DiagnosticError: Error {

let lineNumberWidth = max(3, String(lines.count).count)

let severityLabel = severity.rawValue
let severityColor = severity == .warning ? ANSI.boldYellow : ANSI.boldRed
let header: String = {
guard colorize else {
return "\(displayFileName):\(startLocation.line):\(startLocation.column): error: \(message)"
return "\(displayFileName):\(startLocation.line):\(startLocation.column): \(severityLabel): \(message)"
}
return
"\(displayFileName):\(startLocation.line):\(startLocation.column): \(ANSI.boldRed)error: \(ANSI.boldDefault)\(message)\(ANSI.reset)"
"\(displayFileName):\(startLocation.line):\(startLocation.column): \(severityColor)\(severityLabel): \(ANSI.boldDefault)\(message)\(ANSI.reset)"
}()

let highlightStartColumn = min(max(1, startLocation.column), mainLine.utf8.count + 1)
Expand Down Expand Up @@ -227,8 +236,8 @@ public struct DiagnosticError: Error {
let pointerSpacing = max(0, highlightStartColumn - 1)
let pointerMessage: String = {
let pointer = String(repeating: " ", count: pointerSpacing) + "`- "
guard colorize else { return pointer + "error: \(message)" }
return pointer + "\(ANSI.boldRed)error: \(ANSI.boldDefault)\(message)\(ANSI.reset)"
guard colorize else { return pointer + "\(severityLabel): \(message)" }
return pointer + "\(severityColor)\(severityLabel): \(ANSI.boldDefault)\(message)\(ANSI.reset)"
}()
descriptionParts.append(
Self.formatSourceLine(
Expand Down Expand Up @@ -304,6 +313,7 @@ public struct BridgeJSCoreDiagnosticError: Swift.Error, CustomStringConvertible
private enum ANSI {
static let reset = "\u{001B}[0;0m"
static let boldRed = "\u{001B}[1;31m"
static let boldYellow = "\u{001B}[1;33m"
static let boldDefault = "\u{001B}[1;39m"
static let cyan = "\u{001B}[0;36m"
static let underline = "\u{001B}[4;39m"
Expand Down
104 changes: 84 additions & 20 deletions Plugins/BridgeJS/Sources/BridgeJSCore/SwiftToSkeleton.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,9 @@ public final class SwiftToSkeleton {
private var sourceFiles: [(sourceFile: SourceFileSyntax, inputFilePath: String)] = []
private var usedExternalModules = Set<String>()

/// Non-fatal diagnostics collected during `finalize()`. These do not fail the build.
public private(set) var warnings: [(file: String, diagnostic: DiagnosticError)] = []

public init(
progress: ProgressReporting,
moduleName: String,
Expand Down Expand Up @@ -87,10 +90,15 @@ public final class SwiftToSkeleton {
)
importCollector.walk(sourceFile)

let importErrorsFatal = importCollector.errors.filter { !$0.message.contains("Unsupported type '") }
if !exportCollector.errors.isEmpty || !importErrorsFatal.isEmpty {
let exportErrors = exportCollector.errors.filter { $0.severity == .error }
let importErrorsFatal = importCollector.errors.filter {
$0.severity == .error && !$0.message.contains("Unsupported type '")
}
let fileWarnings = (exportCollector.errors + importCollector.errors).filter { $0.severity == .warning }
warnings.append(contentsOf: fileWarnings.map { (file: inputFilePath, diagnostic: $0) })
if !exportErrors.isEmpty || !importErrorsFatal.isEmpty {
perSourceErrors.append(
(inputFilePath: inputFilePath, errors: exportCollector.errors + importErrorsFatal)
(inputFilePath: inputFilePath, errors: exportErrors + importErrorsFatal)
)
}

Expand Down Expand Up @@ -191,7 +199,40 @@ public final class SwiftToSkeleton {
}

let isAsync = functionType.effectSpecifiers?.asyncSpecifier != nil
let isThrows = functionType.effectSpecifiers?.throwsClause != nil

if isAsync, !returnType.isAsyncResolvable {
errors.append(
DiagnosticError(
node: functionType,
message:
"Returning '\(returnType.swiftType)' from an async closure is not yet supported",
hint:
"Return a type lowerable through the async resolve ABI "
+ "(String/Int/Bool/Double/Float/raw-value or case-only enum/@JS struct/JSObject/Optional/Array/Dictionary), "
+ "or make the closure non-async."
)
)
return nil
}

var isThrows = false
if let throwsClause = functionType.effectSpecifiers?.throwsClause {
guard let thrownType = throwsClause.type,
thrownType.trimmedDescription == "JSException"
else {
errors.append(
DiagnosticError(
node: throwsClause,
message:
"Only JSException is supported for thrown type of Swift closures, "
+ "got \(throwsClause.type?.trimmedDescription ?? "unspecified")",
hint: "Annotate the closure as `throws(JSException)`"
)
)
return nil
}
isThrows = true
}

return .closure(
ClosureSignature(
Expand Down Expand Up @@ -569,6 +610,37 @@ private enum ExportSwiftConstants {
static let supportedRawTypes = SwiftEnumRawType.supportedTypeNames
}

/// Warns about Swift closures handed to JavaScript with an `async throws(JSException)` signature.
/// Captureless closure values lose their thrown error at runtime due to a Swift compiler bug.
private func asyncThrowsClosureWarning(node: some SyntaxProtocol) -> DiagnosticError {
DiagnosticError(
node: node,
message:
"async throwing closures passed to JavaScript may lose thrown errors due to a Swift compiler bug "
+ "(swiftlang/swift#89320) unless the closure value captures state",
hint:
"Pass a closure that captures state, or see the BridgeJS closure documentation for details",
severity: .warning
)
}

extension BridgeType {
fileprivate var containsAsyncThrowsClosure: Bool {
switch self {
case .closure(let signature, _):
return signature.isAsync && signature.isThrows
case .nullable(let wrapped, _):
return wrapped.containsAsyncThrowsClosure
case .array(let element):
return element.containsAsyncThrowsClosure
case .dictionary(let value):
return value.containsAsyncThrowsClosure
default:
return false
}
}
}

extension AttributeSyntax {
/// The attribute name as text when it is a simple identifier (e.g. "JS", "JSFunction").
/// Prefer this over `attributeName.trimmedDescription` for name checks to avoid unnecessary string work.
Expand Down Expand Up @@ -1028,22 +1100,6 @@ private final class ExportSwiftAPICollector: SyntaxAnyVisitor {
guard let type = resolvedType else {
continue // Skip unsupported types
}
if case .closure(let signature, _) = type {
if signature.isAsync {
diagnose(
node: param.type,
message: "Async is not supported for Swift closures yet."
)
continue
}
if signature.isThrows {
diagnose(
node: param.type,
message: "Throws is not supported for Swift closures yet."
)
continue
}
}
if case .nullable(let wrappedType, _) = type, wrappedType.isOptional {
diagnoseNestedOptional(node: param.type, type: param.type.trimmedDescription)
continue
Expand Down Expand Up @@ -1177,6 +1233,9 @@ private final class ExportSwiftAPICollector: SyntaxAnyVisitor {

guard let type = resolvedType else { return nil }
returnType = type
if returnType.containsAsyncThrowsClosure {
errors.append(asyncThrowsClosureWarning(node: returnClause.type))
}
} else {
returnType = .void
}
Expand Down Expand Up @@ -2836,6 +2895,11 @@ private final class ImportSwiftMacrosAPICollector: SyntaxAnyVisitor {
guard let bridgeType = withLookupErrors({ parent.lookupType(for: type, errors: &$0) }) else {
return nil
}
if case .closure(let signature, useJSTypedClosure: true) = bridgeType,
signature.isAsync, signature.isThrows
{
errors.append(asyncThrowsClosureWarning(node: type))
}
let nameToken = param.secondName ?? param.firstName
let name = SwiftToSkeleton.normalizeIdentifier(nameToken.text)
let labelToken = param.secondName == nil ? nil : param.firstName
Expand Down
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