Allow overriding the current logging subsystem

Author: ahoppen

Sources/LSPLogging/Logging.swift

@@ -21,9 +21,6 @@
 
 import Foundation
 
-/// The subsystem that should be used for any logging by default.
-public let subsystem = "org.swift.sourcekit-lsp"
-
 #if canImport(os) && !SOURCEKITLSP_FORCE_NON_DARWIN_LOGGER
 import os  // os_log
 
@@ -44,5 +41,5 @@ public typealias Signposter = NonDarwinSignposter
 
 /// The logger that is used to log any messages.
 public var logger: Logger {
-  Logger(subsystem: subsystem, category: LoggingScope.scope)
+  Logger(subsystem: LoggingScope.subsystem, category: LoggingScope.scope)
 }

Sources/LSPLogging/LoggingScope.swift

@@ -13,15 +13,50 @@
 import Foundation
 
 public final class LoggingScope {
+  /// The name of the current logging subsystem or `nil` if no logging scope is set.
+  @TaskLocal fileprivate static var _subsystem: String?
+
   /// The name of the current logging scope or `nil` if no logging scope is set.
   @TaskLocal fileprivate static var _scope: String?
 
+  /// The name of the current logging subsystem.
+  public static var subsystem: String {
+    return _subsystem ?? "org.swift.sourcekit-lsp"
+  }
+
   /// The name of the current logging scope.
   public static var scope: String {
     return _scope ?? "default"
   }
 }
 
+/// Logs all messages created from the operation to the given subsystem.
+///
+/// This overrides the current logging subsystem.
+///
+/// - Note: Since this stores the logging subsystem in a task-local value, it only works when run inside a task.
+///   Outside a task, this is a no-op.
+public func withLoggingSubsystemAndScope<Result>(
+  subsystem: String,
+  scope: String?,
+  _ operation: () throws -> Result
+) rethrows -> Result {
+  return try LoggingScope.$_subsystem.withValue(subsystem) {
+    return try LoggingScope.$_scope.withValue(scope, operation: operation)
+  }
+}
+
+/// Same as `withLoggingSubsystemAndScope` but allows the operation to be `async`.
+public func withLoggingSubsystemAndScope<Result>(
+  subsystem: String,
+  scope: String?,
+  _ operation: () async throws -> Result
+) async rethrows -> Result {
+  return try await LoggingScope.$_subsystem.withValue(subsystem) {
+    return try await LoggingScope.$_scope.withValue(scope, operation: operation)
+  }
+}
+
 /// Create a new logging scope, which will be used as the category in any log messages created from the operation.
 ///
 /// This overrides the current logging scope.

Sources/SourceKitLSP/Clang/ClangLanguageService.swift

@@ -45,7 +45,7 @@ fileprivate class ClangdStderrLogForwarder {
       //     than 1000 bytes long but if we merge multiple lines into one message, we might easily exceed this limit.
       //  b) It might be confusing why sometimes a single log message contains one line while sometimes it contains
       //     multiple.
-      let logger = Logger(subsystem: subsystem, category: "clangd-stderr")
+      let logger = Logger(subsystem: LoggingScope.subsystem, category: "clangd-stderr")
       logger.info("\(String(data: self.buffer[...newlineIndex], encoding: .utf8) ?? "<invalid UTF-8>")")
       buffer = buffer[buffer.index(after: newlineIndex)...]
     }

Sources/SourceKitLSP/SourceKitLSPServer.swift

@@ -826,7 +826,8 @@ extension SourceKitLSPServer: MessageHandler {
 
     let notificationID = notificationIDForLogging.fetchAndIncrement()
 
-    let signposter = Logger(subsystem: subsystem, category: "notification-\(notificationID)").makeSignposter()
+    let signposter = Logger(subsystem: LoggingScope.subsystem, category: "notification-\(notificationID)")
+      .makeSignposter()
     let signpostID = signposter.makeSignpostID()
     let state = signposter.beginInterval("Notification", id: signpostID, "\(type(of: params))")
     messageHandlingQueue.async(metadata: TaskMetadata(params)) {
@@ -875,7 +876,7 @@ extension SourceKitLSPServer: MessageHandler {
     id: RequestID,
     reply: @escaping (LSPResult<R.Response>) -> Void
   ) {
-    let signposter = Logger(subsystem: subsystem, category: "request-\(id)").makeSignposter()
+    let signposter = Logger(subsystem: LoggingScope.subsystem, category: "request-\(id)").makeSignposter()
     let signpostID = signposter.makeSignpostID()
     let state = signposter.beginInterval("Request", id: signpostID, "\(R.self)")
 

Tests/LSPLoggingTests/LoggingTests.swift

@@ -25,7 +25,7 @@ fileprivate func assertLogging(
   // nonisolated(unsafe) because calls of `assertLogging` do not log to `logHandler` concurrently.
   nonisolated(unsafe) var messages: [String] = []
   let logger = NonDarwinLogger(
-    subsystem: subsystem,
+    subsystem: LoggingScope.subsystem,
     category: "test",
     logLevel: logLevel,
     privacyLevel: privacyLevel,
@@ -75,7 +75,7 @@ final class LoggingTests: XCTestCase {
     // nonisolated(unsafe) because we only have a single call to `logger.log` and that cannot race.
     nonisolated(unsafe) var message: String = ""
     let logger = NonDarwinLogger(
-      subsystem: subsystem,
+      subsystem: LoggingScope.subsystem,
       category: "test",
       logHandler: {
         message = $0