Hoist JSON Lines logic from EntryPoint.swift.

Sources/Testing/ABI/EntryPoints/ABIEntryPoint.swift

@@ -120,7 +120,7 @@ private func entryPoint(
     args?.eventStreamVersion = eventStreamVersionIfNil
   }
 
-  let eventHandler = try eventHandlerForStreamingEvents(version: args?.eventStreamVersion, forwardingTo: recordHandler)
+  let eventHandler = try eventHandlerForStreamingEvents(version: args?.eventStreamVersion, encodeAsJSONLines: false, forwardingTo: recordHandler)
   let exitCode = await entryPoint(passing: args, eventHandler: eventHandler)
 
   // To maintain compatibility with Xcode 16 Beta 1, suppress custom exit codes.

Sources/Testing/ABI/EntryPoints/EntryPoint.swift

@@ -468,8 +468,11 @@ public func configurationForEntryPoint(from args: __CommandLineArguments_v0) thr
   // Event stream output (experimental)
   if let eventStreamOutputPath = args.eventStreamOutputPath {
     let file = try FileHandle(forWritingAtPath: eventStreamOutputPath)
-    let eventHandler = try eventHandlerForStreamingEvents(version: args.eventStreamVersion) { json in
-      try? _writeJSONLine(json, to: file)
+    let eventHandler = try eventHandlerForStreamingEvents(version: args.eventStreamVersion, encodeAsJSONLines: true) { json in
+      _ = try? file.withLock {
+        try file.write(json)
+        try file.write("\n")
+      }
     }
     configuration.eventHandler = { [oldEventHandler = configuration.eventHandler] event, context in
       eventHandler(event, context)
@@ -536,13 +539,20 @@ public func configurationForEntryPoint(from args: __CommandLineArguments_v0) thr
 ///
 /// - Parameters:
 ///   - version: The ABI version to use.
+///   - encodeAsJSONLines: Whether or not to ensure JSON passed to
+///     `eventHandler` is encoded as JSON Lines (i.e. that it does not contain
+///     extra newlines.)
 ///   - eventHandler: The event handler to forward encoded events to. The
 ///     encoding of events depends on `version`.
 ///
 /// - Returns: An event handler.
 ///
 /// - Throws: If `version` is not a supported ABI version.
-func eventHandlerForStreamingEvents(version: Int?, forwardingTo eventHandler: @escaping @Sendable (UnsafeRawBufferPointer) -> Void) throws -> Event.Handler {
+func eventHandlerForStreamingEvents(
+  version: Int?,
+  encodeAsJSONLines: Bool,
+  forwardingTo eventHandler: @escaping @Sendable (UnsafeRawBufferPointer) -> Void
+) throws -> Event.Handler {
   switch version {
 #if !SWT_NO_SNAPSHOT_TYPES
   case -1:
@@ -551,57 +561,11 @@ func eventHandlerForStreamingEvents(version: Int?, forwardingTo eventHandler: @e
     eventHandlerForStreamingEventSnapshots(to: eventHandler)
 #endif
   case nil, 0:
-    ABIv0.Record.eventHandler(forwardingTo: eventHandler)
+    ABIv0.Record.eventHandler(encodeAsJSONLines: encodeAsJSONLines, forwardingTo: eventHandler)
   case let .some(unsupportedVersion):
     throw _EntryPointError.invalidArgument("--event-stream-version", value: "\(unsupportedVersion)")
   }
 }
-
-/// Post-process encoded JSON and write it to a file.
-///
-/// - Parameters:
-///   - json: The JSON to write.
-///   - file: The file to write to.
-///
-/// - Throws: Whatever is thrown when writing to `file`.
-private func _writeJSONLine(_ json: UnsafeRawBufferPointer, to file: borrowing FileHandle) throws {
-  func isASCIINewline(_ byte: UInt8) -> Bool {
-    byte == UInt8(ascii: "\r") || byte == UInt8(ascii: "\n")
-  }
-
-  func write(_ json: UnsafeRawBufferPointer) throws {
-    try file.withLock {
-      try file.write(json)
-      try file.write("\n")
-    }
-  }
-
-  // We don't actually expect the JSON encoder to produce output containing
-  // newline characters, so in debug builds we'll log a diagnostic message.
-  if _slowPath(json.contains(where: isASCIINewline)) {
-#if DEBUG
-    let message = Event.ConsoleOutputRecorder.warning(
-      "JSON encoder produced one or more newline characters while encoding an event to JSON. Please file a bug report at https://github.com/swiftlang/swift-testing/issues/new",
-      options: .for(.stderr)
-    )
-#if SWT_TARGET_OS_APPLE
-    try? FileHandle.stderr.write(message)
-#else
-    print(message)
-#endif
-#endif
-
-    // Remove the newline characters to conform to JSON lines specification.
-    var json = Array(json)
-    json.removeAll(where: isASCIINewline)
-    try json.withUnsafeBytes { json in
-      try write(json)
-    }
-  } else {
-    // No newlines found, no need to copy the buffer.
-    try write(json)
-  }
-}
 #endif
 
 // MARK: - Command-line interface options

Sources/Testing/ABI/v0/ABIv0.Record+Streaming.swift

@@ -10,10 +10,46 @@
 
 #if canImport(Foundation) && (!SWT_NO_FILE_IO || !SWT_NO_ABI_ENTRY_POINT)
 extension ABIv0.Record {
+  /// Post-process encoded JSON and write it to a file.
+  ///
+  /// - Parameters:
+  ///   - json: The JSON to write.
+  ///   - file: The file to write to.
+  ///
+  /// - Throws: Whatever is thrown when writing to `file`.
+  private static func _asJSONLine(_ json: UnsafeRawBufferPointer, _ eventHandler: (_ recordJSON: UnsafeRawBufferPointer) throws -> Void) rethrows {
+    // We don't actually expect the JSON encoder to produce output containing
+    // newline characters, so in debug builds we'll log a diagnostic message.
+    if _slowPath(json.contains(where: \.isASCIINewline)) {
+  #if DEBUG
+      let message = Event.ConsoleOutputRecorder.warning(
+        "JSON encoder produced one or more newline characters while encoding an event to JSON. Please file a bug report at https://github.com/swiftlang/swift-testing/issues/new",
+        options: .for(.stderr)
+      )
+  #if SWT_TARGET_OS_APPLE
+      try? FileHandle.stderr.write(message)
+  #else
+      print(message)
+  #endif
+  #endif
+
+      // Remove the newline characters to conform to JSON lines specification.
+      var json = Array(json)
+      json.removeAll(where: \.isASCIINewline)
+      try json.withUnsafeBytes(eventHandler)
+    } else {
+      // No newlines found, no need to copy the buffer.
+      try eventHandler(json)
+    }
+  }
+
   /// Create an event handler that encodes events as JSON and forwards them to
   /// an ABI-friendly event handler.
   ///
   /// - Parameters:
+  ///   - encodeAsJSONLines: Whether or not to ensure JSON passed to
+  ///     `eventHandler` is encoded as JSON Lines (i.e. that it does not contain
+  ///     extra newlines.)
   ///   - eventHandler: The event handler to forward events to. See
   ///     ``ABIv0/EntryPoint-swift.typealias`` for more information.
   ///
@@ -27,10 +63,17 @@ extension ABIv0.Record {
   /// performs additional postprocessing before writing JSON data to ensure it
   /// does not contain any newline characters.
   static func eventHandler(
+    encodeAsJSONLines: Bool,
     forwardingTo eventHandler: @escaping @Sendable (_ recordJSON: UnsafeRawBufferPointer) -> Void
   ) -> Event.Handler {
+    // Encode as JSON Lines if requested.
+    var eventHandlerCopy = eventHandler
+    if encodeAsJSONLines {
+      eventHandlerCopy = { @Sendable in _asJSONLine($0, eventHandler) }
+    }
+
     let humanReadableOutputRecorder = Event.HumanReadableOutputRecorder()
-    return { event, context in
+    return { [eventHandler = eventHandlerCopy] event, context in
       if case .testDiscovered = event.kind, let test = context.test {
         try? JSON.withEncoding(of: Self(encoding: test)) { testJSON in
           eventHandler(testJSON)

Sources/Testing/Support/Additions/NumericAdditions.swift

@@ -25,3 +25,12 @@ extension Numeric {
     return "\(self) \(noun)s"
   }
 }
+
+// MARK: -
+
+extension UInt8 {
+  /// Whether or not this instance is an ASCII newline character (`\n` or `\r`).
+  var isASCIINewline: Bool {
+    self == UInt8(ascii: "\r") || self == UInt8(ascii: "\n")
+  }
+}

Tests/TestingTests/SwiftPMTests.swift

@@ -228,7 +228,7 @@ struct SwiftPMTests {
 
   func decodeABIv0RecordStream(fromFileAtPath path: String) throws -> [ABIv0.Record] {
     try FileHandle(forReadingAtPath: path).readToEnd()
-      .split(separator: 10) // "\n"
+      .split(whereSeparator: \.isASCIINewline)
       .map { line in
         try line.withUnsafeBytes { line in
           try JSON.decode(ABIv0.Record.self, from: line)