Factor out the new code to its own file

Author: grynspan

Sources/Testing/ABI/Encoded/ABI.EncodedIssue.swift

@@ -112,7 +112,7 @@ extension Issue {
       // TODO: improve fidelity of issue kind reporting (especially those without associated values)
       .unconditional
     }
-    let severity: Issue.Severity = switch issue._severity {
+    let severity: Issue.Severity = switch issue.severity {
     case .warning:
         .warning
     case nil, .error:

Sources/Testing/CMakeLists.txt

@@ -29,6 +29,7 @@ add_library(Testing
   Attachments/Attachment.swift
   Events/Clock.swift
   Events/Event.swift
+  Events/Event+FallbackHandler.swift
   Events/Recorder/Event.AdvancedConsoleOutputRecorder.swift
   Events/Recorder/Event.ConsoleOutputRecorder.swift
   Events/Recorder/Event.HumanReadableOutputRecorder.swift

Sources/Testing/Events/Event+FallbackHandler.swift

@@ -0,0 +1,94 @@
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for Swift project authors
+//
+
+private import _Testing_ExperimentalInfrastructure
+
+extension Event {
+  /// The implementation of ``fallbackEventHandler``.
+  ///
+  /// - Parameters:
+  ///   - abi: The ABI version to use for decoding `recordJSON`.
+  ///   - recordJSON: The JSON encoding of an event record.
+  ///
+  /// - Throws: Any error that prevented handling the encoded record.
+  private static func _fallbackEventHandler<V>(_ abi: V.Type, _ recordJSON: UnsafeRawBufferPointer) throws where V: ABI.Version {
+    let record = try JSON.decode(ABI.Record<ABI.CurrentVersion>.self, from: recordJSON)
+    guard case let .event(event) = record.kind else {
+      return
+    }
+    switch event.kind {
+    case .issueRecorded:
+      Issue(event)?.record()
+    case .valueAttached:
+      if let attachment = event.attachment {
+        Attachment.record(attachment, sourceLocation: attachment._sourceLocation ?? .__here())
+      }
+    default:
+      // Not handled here.
+      break
+    }
+  }
+
+  /// The fallback event handler to set when Swift Testing is the active testing
+  /// library.
+  private static let _fallbackEventHandler: FallbackEventHandler = { recordJSONSchemaVersionNumber, recordJSONBaseAddress, recordJSONByteCount, _ in
+    let abi = String(validatingCString: recordJSONSchemaVersionNumber)
+      .flatMap(VersionNumber.init)
+      .flatMap(ABI.version(forVersionNumber:))
+    if let abi {
+      let recordJSON = UnsafeRawBufferPointer(start: recordJSONBaseAddress, count: recordJSONByteCount)
+      try! Self._fallbackEventHandler(abi, recordJSON)
+    }
+  }
+
+  /// The implementation of ``installFallbackEventHandler()``.
+  private static let _installFallbackHandler: Bool = {
+    _Testing_ExperimentalInfrastructure.installFallbackEventHandler(Self._fallbackEventHandler)
+  }()
+
+  /// Install the testing library's fallback event handler.
+  ///
+  /// - Returns: Whether or not the handler was installed.
+  static func installFallbackHandler() -> Bool {
+    _installFallbackHandler
+  }
+
+  /// Post this event to the currently-installed fallback event handler.
+  ///
+  /// - Parameters:
+  ///   - context: The context associated with this event.
+  ///
+  /// - Returns: Whether or not the fallback event handler was invoked. If the
+  ///   currently-installed handler belongs to the testing library, returns
+  ///   `false`.
+  borrowing func postToFallbackHandler(in context: borrowing Context) -> Bool {
+    guard let fallbackEventHandler = _Testing_ExperimentalInfrastructure.fallbackEventHandler() else {
+      // No fallback event handler is installed.
+      return false
+    }
+    if castCFunction(fallbackEventHandler, to: UnsafeRawPointer.self) == castCFunction(Self._fallbackEventHandler, to: UnsafeRawPointer.self) {
+      // The fallback event handler belongs to Swift Testing, so we don't want
+      // to call it on our own behalf.
+      return false
+    }
+
+    // Encode the event as JSON and pass it to the handler.
+    let encodeAndInvoke = ABI.CurrentVersion.eventHandler(encodeAsJSONLines: false) { recordJSON in
+      fallbackEventHandler(
+        String(describing: ABI.CurrentVersion.versionNumber),
+        recordJSON.baseAddress!,
+        recordJSON.count,
+        nil
+      )
+    }
+    encodeAndInvoke(self, context)
+    return true
+  }
+}

Sources/Testing/Events/Event.swift

@@ -8,8 +8,6 @@
 // See https://swift.org/CONTRIBUTORS.txt for Swift project authors
 //
 
-internal import _Testing_ExperimentalInfrastructure
-
 /// An event that occurred during testing.
 @_spi(ForToolsIntegrationOnly)
 public struct Event: Sendable {
@@ -272,60 +270,6 @@ extension Event {
     }
   }
 
-  /// The implementation of ``fallbackEventHandler``.
-  ///
-  /// - Parameters:
-  ///   - abi: The ABI version to use for decoding `recordJSON`.
-  ///   - recordJSON: The JSON encoding of an event record.
-  ///
-  /// - Throws: Any error that prevented handling the encoded record.
-  private static func _fallbackEventHandler<V>(_ abi: V.Type, _ recordJSON: UnsafeRawBufferPointer) throws where V: ABI.Version {
-    let record = try JSON.decode(ABI.Record<ABI.CurrentVersion>.self, from: recordJSON)
-    guard case let .event(event) = record.kind else {
-      return
-    }
-    switch event.kind {
-    case .issueRecorded:
-      Issue(event)?.record()
-    case .valueAttached:
-      if let attachment = event.attachment {
-        Attachment.record(attachment, sourceLocation: attachment._sourceLocation ?? .__here())
-      }
-    default:
-      // Not handled here.
-      break
-    }
-  }
-
-  /// The fallback event handler to set when Swift Testing is the active testing
-  /// library.
-  ///
-  /// ## See Also
-  ///
-  /// - `swift_testing_getFallbackEventHandler()`
-  /// - `swift_testing_setFallbackEventHandler()`
-  static let fallbackEventHandler: FallbackEventHandler = { recordJSONSchemaVersionNumber, recordJSONBaseAddress, recordJSONByteCount, _ in
-    let abi = String(validatingCString: recordJSONSchemaVersionNumber)
-      .flatMap(VersionNumber.init)
-      .flatMap(ABI.version(forVersionNumber:))
-    if let abi {
-      let recordJSON = UnsafeRawBufferPointer(start: recordJSONBaseAddress, count: recordJSONByteCount)
-      try! Self._fallbackEventHandler(abi, recordJSON)
-    }
-  }
-
-  /// The implementation of ``installFallbackEventHandler()``.
-  private static let _installFallbackHandler: Bool = {
-    _Testing_ExperimentalInfrastructure.installFallbackEventHandler(Self.fallbackEventHandler)
-  }()
-
-  /// Install the testing library's fallback event handler.
-  ///
-  /// - Returns: Whether or not the handler was installed.
-  static func installFallbackHandler() -> Bool {
-    _installFallbackHandler
-  }
-
   /// Post this event to the currently-installed event handler.
   ///
   /// - Parameters:
@@ -348,19 +292,8 @@ extension Event {
       if configuration.eventHandlingOptions.shouldHandleEvent(self) {
         configuration.handleEvent(self, in: context)
       }
-    } else if let fallbackEventHandler = _Testing_ExperimentalInfrastructure.fallbackEventHandler(),
-              castCFunction(fallbackEventHandler, to: UnsafeRawPointer.self) != castCFunction(Self.fallbackEventHandler, to: UnsafeRawPointer.self) {
-      // Some library other than Swift Testing has set a fallback event handler.
-      // Encode the event as JSON and call it.
-      let fallbackEventHandler = ABI.CurrentVersion.eventHandler(encodeAsJSONLines: false) { recordJSON in
-        fallbackEventHandler(
-          String(describing: ABI.CurrentVersion.versionNumber),
-          recordJSON.baseAddress!,
-          recordJSON.count,
-          nil
-        )
-      }
-      fallbackEventHandler(self, context)
+    } else if postToFallbackHandler(in: context) {
+      // The fallback event handler handled this event.
     } else {
       // The current task does NOT have an associated configuration. This event
       // will be lost! Post it to every registered event handler to avoid that.

Sources/_Testing_ExperimentalInfrastructure/FallbackEventHandler.swift

@@ -19,7 +19,6 @@ private import _TestingInternals
 ///   - recordJSONBaseAddress: A pointer to the first byte of the encoded event.
 ///   - recordJSONByteCount: The size of the encoded event in bytes.
 ///   - reserved: Reserved for future use.
-@usableFromInline
 package typealias FallbackEventHandler = @Sendable @convention(c) (
   _ recordJSONSchemaVersionNumber: UnsafePointer<CChar>,
   _ recordJSONBaseAddress: UnsafeRawPointer,
@@ -36,7 +35,6 @@ package typealias FallbackEventHandler = @Sendable @convention(c) (
 ///   exchange the previous value with a new value, call
 ///   ``setFallbackEventHandler(_:)`` and store its returned value.
 @_cdecl("swift_testing_getFallbackEventHandler")
-@usableFromInline
 package func fallbackEventHandler() -> FallbackEventHandler? {
   swt_loadFallbackEventHandler()
 }
@@ -52,7 +50,6 @@ package func fallbackEventHandler() -> FallbackEventHandler? {
 /// by the first testing library to run. If this function has already been
 /// called and the handler set, it does not replace the previous handler.
 @_cdecl("swift_testing_installFallbackEventHandler")
-@usableFromInline
 package func installFallbackEventHandler(_ handler: FallbackEventHandler) -> CBool {
   swt_installFallbackEventHandler(handler)
 }