Make the SourceKitLSP module build in Swift 6 mode

Swift 6 mode didn’t find any notable data races. But it’s good to know Swift 6 will prevent future ones.

Author: ahoppen

Sources/LSPLogging/Logging.swift

@@ -28,6 +28,16 @@ public typealias LogLevel = os.OSLogType
 public typealias Logger = os.Logger
 public typealias Signposter = OSSignposter
 
+#if compiler(<5.11)
+extension OSSignposter: @unchecked Sendable {}
+extension OSSignpostID: @unchecked Sendable {}
+extension OSSignpostIntervalState: @unchecked Sendable {}
+#else
+extension OSSignposter: @retroactive @unchecked Sendable {}
+extension OSSignpostID: @retroactive @unchecked Sendable {}
+extension OSSignpostIntervalState: @retroactive @unchecked Sendable {}
+#endif
+
 extension os.Logger {
   public func makeSignposter() -> Signposter {
     return OSSignposter(logger: self)

Sources/LSPLogging/LoggingScope.swift

@@ -80,7 +80,7 @@ public func withLoggingScope<Result>(
 /// - SeeAlso: ``withLoggingScope(_:_:)-6qtga``
 public func withLoggingScope<Result>(
   _ scope: String,
-  _ operation: () async throws -> Result
+  @_inheritActorContext _ operation: @Sendable () async throws -> Result
 ) async rethrows -> Result {
   return try await LoggingScope.$_scope.withValue(
     scope,

Sources/LSPLogging/NonDarwinLogging.swift

@@ -361,14 +361,14 @@ public struct NonDarwinLogger: Sendable {
 
 // MARK: - Signposter
 
-public struct NonDarwinSignpostID {}
+public struct NonDarwinSignpostID: Sendable {}
 
-public struct NonDarwinSignpostIntervalState {}
+public struct NonDarwinSignpostIntervalState: Sendable {}
 
 /// A type that is API-compatible to `OSLogMessage` for all uses within sourcekit-lsp.
 ///
 /// Since non-Darwin platforms don't have signposts, the type just has no-op operations.
-public struct NonDarwinSignposter {
+public struct NonDarwinSignposter: Sendable {
   public func makeSignpostID() -> NonDarwinSignpostID {
     return NonDarwinSignpostID()
   }

Sources/LanguageServerProtocol/Connection.swift

@@ -44,7 +44,7 @@ public protocol MessageHandler: AnyObject, Sendable {
   func handle<Request: RequestType>(
     _ request: Request,
     id: RequestID,
-    reply: @escaping (LSPResult<Request.Response>) -> Void
+    reply: @Sendable @escaping (LSPResult<Request.Response>) -> Void
   )
 }
 
@@ -110,7 +110,7 @@ public final class LocalConnection: Connection, @unchecked Sendable {
 
   public func send<Request: RequestType>(
     _ request: Request,
-    reply: @escaping (LSPResult<Request.Response>) -> Void
+    reply: @Sendable @escaping (LSPResult<Request.Response>) -> Void
   ) -> RequestID {
     let id = nextRequestID()
 

Sources/LanguageServerProtocol/Message.swift

@@ -24,7 +24,7 @@ public protocol _RequestType: MessageType {
   func _handle(
     _ handler: MessageHandler,
     id: RequestID,
-    reply: @escaping (LSPResult<ResponseType>, RequestID) -> Void
+    reply: @Sendable @escaping (LSPResult<ResponseType>, RequestID) -> Void
   )
 }
 
@@ -49,7 +49,7 @@ extension RequestType {
   public func _handle(
     _ handler: MessageHandler,
     id: RequestID,
-    reply: @escaping (LSPResult<ResponseType>, RequestID) -> Void
+    reply: @Sendable @escaping (LSPResult<ResponseType>, RequestID) -> Void
   ) {
     handler.handle(self, id: id) { response in
       reply(response.map({ $0 as ResponseType }), id)

Sources/LanguageServerProtocol/Requests/CodeActionRequest.swift

@@ -10,7 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-public typealias CodeActionProvider = (CodeActionRequest) async throws -> [CodeAction]
+public typealias CodeActionProvider = @Sendable (CodeActionRequest) async throws -> [CodeAction]
 
 /// Request for returning all possible code actions for a given text document and range.
 ///

Sources/LanguageServerProtocol/SupportTypes/ServerCapabilities.swift

@@ -587,7 +587,7 @@ public struct DocumentRangeFormattingOptions: WorkDoneProgressOptions, Codable,
   }
 }
 
-public struct FoldingRangeOptions: Codable, Hashable {
+public struct FoldingRangeOptions: Codable, Hashable, Sendable {
   /// Currently empty in the spec.
   public init() {}
 }

Sources/SKCore/BuildSystemManager.swift

@@ -17,6 +17,10 @@ import LanguageServerProtocol
 
 import struct TSCBasic.AbsolutePath
 
+#if canImport(os)
+import os
+#endif
+
 /// `BuildSystem` that integrates client-side information such as main-file lookup as well as providing
 ///  common functionality such as caching.
 ///
@@ -169,7 +173,7 @@ extension BuildSystemManager {
       logger.error("Getting build settings failed: \(error.forLogging)")
     }
 
-    guard var settings = fallbackBuildSystem?.buildSettings(for: document, language: language) else {
+    guard var settings = await fallbackBuildSystem?.buildSettings(for: document, language: language) else {
       return nil
     }
     if buildSystem == nil {

Sources/SKCore/FallbackBuildSystem.swift

@@ -21,7 +21,7 @@ import struct TSCBasic.AbsolutePath
 import class TSCBasic.Process
 
 /// A simple BuildSystem suitable as a fallback when accurate settings are unknown.
-public final class FallbackBuildSystem {
+public actor FallbackBuildSystem {
 
   let buildSetup: BuildSetup
 
@@ -38,6 +38,10 @@ public final class FallbackBuildSystem {
     )
   }()
 
+  @_spi(Testing) public func setSdkPath(_ newValue: AbsolutePath?) {
+    self.sdkpath = newValue
+  }
+
   /// Delegate to handle any build system events.
   public weak var delegate: BuildSystemDelegate? = nil
 

Sources/SKSupport/LineTable.swift

@@ -11,8 +11,11 @@
 //===----------------------------------------------------------------------===//
 
 import LSPLogging
+#if canImport(os)
+import os
+#endif
 
-public struct LineTable: Hashable {
+public struct LineTable: Hashable, Sendable {
   @usableFromInline
   var impl: [String.Index]
 

Sources/SKSupport/ThreadSafeBox.swift

@@ -47,6 +47,12 @@ public class ThreadSafeBox<T>: @unchecked Sendable {
     _value = initialValue
   }
 
+  public func withLock<Result>(_ body: (inout T) -> Result) -> Result {
+    return lock.withLock {
+      return body(&_value)
+    }
+  }
+
   /// If the value in the box is an optional, return it and reset it to `nil`
   /// in an atomic operation.
   public func takeValue<U>() -> T where U? == T {

Sources/SourceKitLSP/Clang/ClangLanguageService.swift

@@ -33,10 +33,13 @@ extension NSLock {
 }
 
 /// Gathers data from clangd's stderr pipe. When it has accumulated a full line, writes the the line to the logger.
-fileprivate class ClangdStderrLogForwarder {
+fileprivate actor ClangdStderrLogForwarder {
+  /// Queue on which all data from `clangd`’s stderr will be forwarded to `stderr`. This allows us to have a
+  /// nonisolated `handle` function but ensure that data gets processed in order.
+  private let queue = AsyncQueue<Serial>()
   private var buffer = Data()
 
-  func handle(_ newData: Data) {
+  private func handleImpl(_ newData: Data) {
     self.buffer += newData
     while let newlineIndex = self.buffer.firstIndex(of: UInt8(ascii: "\n")) {
       // Output a separate log message for every line in clangd's stderr.
@@ -50,6 +53,12 @@ fileprivate class ClangdStderrLogForwarder {
       buffer = buffer[buffer.index(after: newlineIndex)...]
     }
   }
+
+  nonisolated func handle(_ newData: Data) {
+    queue.async {
+      await self.handleImpl(newData)
+    }
+  }
 }
 
 /// A thin wrapper over a connection to a clangd server providing build setting handling.
@@ -328,7 +337,7 @@ actor ClangLanguageService: LanguageService, MessageHandler {
   nonisolated func handle<R: RequestType>(
     _ params: R,
     id: RequestID,
-    reply: @escaping (LSPResult<R.Response>) -> Void
+    reply: @Sendable @escaping (LSPResult<R.Response>) -> Void
   ) {
     logger.info(
       """
@@ -442,10 +451,11 @@ extension ClangLanguageService {
   }
 
   public func shutdown() async {
+    let clangd = clangd!
     await withCheckedContinuation { continuation in
       _ = clangd.send(ShutdownRequest()) { _ in
         Task {
-          await self.clangd.send(ExitNotification())
+          clangd.send(ExitNotification())
           continuation.resume()
         }
       }

Sources/SourceKitLSP/DocumentManager.swift

@@ -23,10 +23,10 @@ import SwiftSyntax
 /// data structure that is stored internally by the ``DocumentManager`` is a
 /// ``Document``. The purpose of a ``DocumentSnapshot`` is to be able to work
 /// with one version of a document without having to think about it changing.
-public struct DocumentSnapshot: Identifiable {
+public struct DocumentSnapshot: Identifiable, Sendable {
   /// An ID that uniquely identifies the version of the document stored in this
   /// snapshot.
-  public struct ID: Hashable, Comparable {
+  public struct ID: Hashable, Comparable, Sendable {
     public let uri: DocumentURI
     public let version: Int
 
@@ -84,16 +84,18 @@ public final class Document {
   }
 }
 
-public final class DocumentManager: InMemoryDocumentManager {
+public final class DocumentManager: InMemoryDocumentManager, Sendable {
 
   public enum Error: Swift.Error {
     case alreadyOpen(DocumentURI)
     case missingDocument(DocumentURI)
   }
 
-  let queue: DispatchQueue = DispatchQueue(label: "document-manager-queue")
+  // FIXME: (async) Migrate this to be an AsyncQueue
+  private let queue: DispatchQueue = DispatchQueue(label: "document-manager-queue")
 
-  var documents: [DocumentURI: Document] = [:]
+  // `nonisolated(unsafe)` is fine because `documents` is guarded by queue.
+  nonisolated(unsafe) var documents: [DocumentURI: Document] = [:]
 
   public init() {}
 

Sources/SourceKitLSP/LanguageService.swift

@@ -24,7 +24,7 @@ public enum LanguageServerState {
   case semanticFunctionalityDisabled
 }
 
-public struct RenameLocation {
+public struct RenameLocation: Sendable {
   /// How the identifier at a given location is being used.
   ///
   /// This is primarily used to influence how argument labels should be renamed in Swift and if a location should be
@@ -64,7 +64,7 @@ public struct RenameLocation {
 ///
 /// For example, we may have a language service that provides semantic functionality for c-family using a clangd server,
 /// launched from a specific toolchain or from sourcekitd.
-public protocol LanguageService: AnyObject {
+public protocol LanguageService: AnyObject, Sendable {
 
   // MARK: - Creation
 
@@ -90,7 +90,7 @@ public protocol LanguageService: AnyObject {
 
   /// Add a handler that is called whenever the state of the language server changes.
   func addStateChangeHandler(
-    handler: @escaping (_ oldState: LanguageServerState, _ newState: LanguageServerState) -> Void
+    handler: @Sendable @escaping (_ oldState: LanguageServerState, _ newState: LanguageServerState) -> Void
   ) async
 
   // MARK: - Text synchronization

Sources/SourceKitLSP/Rename.swift

@@ -10,7 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-import IndexStoreDB
+@preconcurrency import IndexStoreDB
 import LSPLogging
 import LanguageServerProtocol
 import SKSupport
@@ -445,7 +445,7 @@ extension SwiftLanguageService {
 /// These names might differ. For example, an Objective-C method gets translated by the clang importer to form the Swift
 /// name or it could have a `SWIFT_NAME` attribute that defines the method's name in Swift. Similarly, a Swift symbol
 /// might specify the name by which it gets exposed to Objective-C using the `@objc` attribute.
-public struct CrossLanguageName {
+public struct CrossLanguageName: Sendable {
   /// The name of the symbol in clang languages or `nil` if the symbol is defined in Swift, doesn't have any references
   /// from clang languages and thus hasn't been translated.
   fileprivate let clangName: String?
@@ -564,6 +564,22 @@ extension SourceKitLSPServer {
     return nil
   }
 
+  // FIXME: (async-workaround): Needed to work around rdar://127977642
+  private func translateClangNameToSwift(
+    _ swiftLanguageService: SwiftLanguageService,
+    at symbolLocation: SymbolLocation,
+    in snapshot: DocumentSnapshot,
+    isObjectiveCSelector: Bool,
+    name: String
+  ) async throws -> String {
+    return try await swiftLanguageService.translateClangNameToSwift(
+      at: symbolLocation,
+      in: snapshot,
+      isObjectiveCSelector: isObjectiveCSelector,
+      name: name
+    )
+  }
+
   private func getCrossLanguageName(
     forDefinitionOccurrence definitionOccurrence: SymbolOccurrence,
     overrideName: String? = nil,
@@ -598,7 +614,8 @@ extension SourceKitLSPServer {
       let swiftName: String?
       if let swiftReference = await getReferenceFromSwift(usr: usr, index: index, workspace: workspace) {
         let isObjectiveCSelector = definitionLanguage == .objective_c && definitionSymbol.kind.isMethod
-        swiftName = try await swiftReference.swiftLanguageService.translateClangNameToSwift(
+        swiftName = try await self.translateClangNameToSwift(
+          swiftReference.swiftLanguageService,
           at: swiftReference.location,
           in: swiftReference.snapshot,
           isObjectiveCSelector: isObjectiveCSelector,
@@ -670,7 +687,7 @@ extension SourceKitLSPServer {
     guard let workspace = await workspaceForDocument(uri: uri) else {
       throw ResponseError.workspaceNotOpen(uri)
     }
-    guard let primaryFileLanguageService = workspace.documentService[uri] else {
+    guard let primaryFileLanguageService = workspace.documentService.value[uri] else {
       return nil
     }
 
@@ -716,24 +733,26 @@ extension SourceKitLSPServer {
     var locationsByFile: [URL: [RenameLocation]] = [:]
 
     actor LanguageServerTypesCache {
-      let index: CheckedIndex
+      let index: UncheckedIndex
       var languageServerTypesCache: [URL: LanguageServerType?] = [:]
 
-      init(index: CheckedIndex) {
+      init(index: UncheckedIndex) {
         self.index = index
       }
 
       func languageServerType(for url: URL) -> LanguageServerType? {
         if let cachedValue = languageServerTypesCache[url] {
           return cachedValue
         }
-        let serverType = LanguageServerType(symbolProvider: index.symbolProvider(for: url.path))
+        let serverType = LanguageServerType(
+          symbolProvider: index.checked(for: .deletedFiles).symbolProvider(for: url.path)
+        )
         languageServerTypesCache[url] = serverType
         return serverType
       }
     }
 
-    let languageServerTypesCache = LanguageServerTypesCache(index: index)
+    let languageServerTypesCache = LanguageServerTypesCache(index: index.unchecked)
 
     let usrsToRename = overridingAndOverriddenUsrs(of: usr, index: index)
     let occurrencesToRename = usrsToRename.flatMap { index.occurrences(ofUSR: $0, roles: renameRoles) }

Sources/SourceKitLSP/Sequence+AsyncMap.swift

@@ -13,7 +13,7 @@
 extension Sequence {
   /// Just like `Sequence.map` but allows an `async` transform function.
   func asyncMap<T>(
-    _ transform: (Element) async throws -> T
+    @_inheritActorContext _ transform: @Sendable (Element) async throws -> T
   ) async rethrows -> [T] {
     var result: [T] = []
     result.reserveCapacity(self.underestimatedCount)
@@ -27,7 +27,7 @@ extension Sequence {
 
   /// Just like `Sequence.compactMap` but allows an `async` transform function.
   func asyncCompactMap<T>(
-    _ transform: (Element) async throws -> T?
+    @_inheritActorContext _ transform: @Sendable (Element) async throws -> T?
   ) async rethrows -> [T] {
     var result: [T] = []