Mark image attachments as unavailable on non-Darwin/non-Windows.

.github/workflows/pull_request.yml

@@ -24,6 +24,6 @@ jobs:
     uses: swiftlang/github-workflows/.github/workflows/soundness.yml@main
     with:
       license_header_check_project_name: "Swift"
-      docs_check_container_image: "swift:6.2-noble"
+      docs_check_enabled: false
       format_check_enabled: false
       api_breakage_check_enabled: false

Package.swift

@@ -383,6 +383,7 @@ extension Array where Element == PackageDescription.SwiftSetting {
       .define("SWT_NO_DYNAMIC_LINKING", .whenEmbedded(or: .when(platforms: [.wasi]))),
       .define("SWT_NO_PIPES", .whenEmbedded(or: .when(platforms: [.wasi]))),
       .define("SWT_NO_FOUNDATION_FILE_COORDINATION", .whenEmbedded(or: .whenApple(false))),
+      .define("SWT_NO_IMAGE_ATTACHMENTS", .whenEmbedded(or: .when(platforms: [.linux, .custom("freebsd"), .openbsd, .wasi, .android]))),
 
       .define("SWT_NO_LEGACY_TEST_DISCOVERY", .whenEmbedded()),
       .define("SWT_NO_LIBDISPATCH", .whenEmbedded()),

Sources/Testing/Attachments/Images/AttachableImageFormat.swift

@@ -31,6 +31,9 @@
 /// @Metadata {
 ///   @Available(Swift, introduced: 6.3)
 /// }
+#if SWT_NO_IMAGE_ATTACHMENTS
+@available(*, unavailable, message: "Image attachments are not available on this platform.")
+#endif
 @available(_uttypesAPI, *)
 public struct AttachableImageFormat: Sendable {
   /// An enumeration describing the various kinds of image format that can be
@@ -77,6 +80,9 @@ public struct AttachableImageFormat: Sendable {
 
 // MARK: -
 
+#if SWT_NO_IMAGE_ATTACHMENTS
+@available(*, unavailable, message: "Image attachments are not available on this platform.")
+#endif
 @available(_uttypesAPI, *)
 extension AttachableImageFormat {
   /// The PNG image format.

Sources/Testing/Attachments/Images/Attachment+_AttachableAsImage.swift

@@ -8,6 +8,9 @@
 // See https://swift.org/CONTRIBUTORS.txt for Swift project authors
 //
 
+#if SWT_NO_IMAGE_ATTACHMENTS
+@available(*, unavailable, message: "Image attachments are not available on this platform.")
+#endif
 @available(_uttypesAPI, *)
 extension Attachment {
   /// Initialize an instance of this type that encloses the given image.
@@ -101,6 +104,9 @@ extension Attachment {
 // MARK: -
 
 @_spi(Experimental) // STOP: not part of ST-0014
+#if SWT_NO_IMAGE_ATTACHMENTS
+@available(*, unavailable, message: "Image attachments are not available on this platform.")
+#endif
 @available(_uttypesAPI, *)
 extension Attachment where AttachableValue: AttachableWrapper, AttachableValue.Wrapped: _AttachableAsImage {
   /// The image format to use when encoding the represented image.

Sources/Testing/Attachments/Images/ImageAttachmentError.swift

@@ -11,6 +11,9 @@
 private import _TestingInternals
 
 /// A type representing an error that can occur when attaching an image.
+#if SWT_NO_IMAGE_ATTACHMENTS
+@available(*, unavailable, message: "Image attachments are not available on this platform.")
+#endif
 package enum ImageAttachmentError: Error {
 #if SWT_TARGET_OS_APPLE
   /// The image could not be converted to an instance of `CGImage`.
@@ -39,6 +42,9 @@ package enum ImageAttachmentError: Error {
 #endif
 }
 
+#if SWT_NO_IMAGE_ATTACHMENTS
+@available(*, unavailable, message: "Image attachments are not available on this platform.")
+#endif
 extension ImageAttachmentError: CustomStringConvertible {
   package var description: String {
 #if SWT_TARGET_OS_APPLE

Sources/Testing/Attachments/Images/_AttachableAsImage.swift

@@ -8,6 +8,14 @@
 // See https://swift.org/CONTRIBUTORS.txt for Swift project authors
 //
 
+#if SWT_TARGET_OS_APPLE
+// Image attachments on Apple platforms conform to AttachableAsCGImage.
+#elseif os(Windows)
+// Image attachments on Windows platforms conform to AttachableAsIWICBitmapSource.
+#elseif !SWT_NO_IMAGE_ATTACHMENTS
+#error("Platform-specific misconfiguration: support for image attachments requires a platform-specific implementation")
+#endif
+
 /// A protocol describing images that can be converted to instances of
 /// [`Attachment`](https://developer.apple.com/documentation/testing/attachment).
 ///
@@ -18,6 +26,9 @@
 ///   A future Swift Evolution proposal will promote this protocol to API so
 ///   that we don't need to underscore its name.
 /// }
+#if SWT_NO_IMAGE_ATTACHMENTS
+@available(*, unavailable, message: "Image attachments are not available on this platform.")
+#endif
 @available(_uttypesAPI, *)
 public protocol _AttachableAsImage: SendableMetatype {
   /// Make a copy of this instance to pass to an attachment.

Sources/Testing/Attachments/Images/_AttachableImageWrapper.swift

@@ -20,6 +20,9 @@
 /// @Comment {
 /// | Windows | [`HBITMAP`](https://learn.microsoft.com/en-us/windows/win32/gdi/bitmaps), [`HICON`](https://learn.microsoft.com/en-us/windows/win32/menurc/icons), [`IWICBitmapSource`](https://learn.microsoft.com/en-us/windows/win32/api/wincodec/nn-wincodec-iwicbitmapsource) (including its subclasses declared by Windows Imaging Component) |
 /// }
+#if SWT_NO_IMAGE_ATTACHMENTS
+@available(*, unavailable, message: "Image attachments are not available on this platform.")
+#endif
 @available(_uttypesAPI, *)
 public final class _AttachableImageWrapper<Image>: Sendable where Image: _AttachableAsImage {
   /// The underlying image.
@@ -38,6 +41,9 @@ public final class _AttachableImageWrapper<Image>: Sendable where Image: _Attach
   }
 }
 
+#if SWT_NO_IMAGE_ATTACHMENTS
+@available(*, unavailable, message: "Image attachments are not available on this platform.")
+#endif
 @available(_uttypesAPI, *)
 extension _AttachableImageWrapper {
   public var wrappedValue: Image {

cmake/modules/shared/CompilerSettings.cmake

@@ -42,6 +42,9 @@ if(CMAKE_SYSTEM_NAME STREQUAL "WASI")
   add_compile_definitions("SWT_NO_DYNAMIC_LINKING")
   add_compile_definitions("SWT_NO_PIPES")
 endif()
+if (NOT (APPLE OR CMAKE_SYSTEM_NAME STREQUAL "Windows"))
+  add_compile_definitions("SWT_NO_IMAGE_ATTACHMENTS")
+endif()
 
 file(STRINGS "${SWT_SOURCE_ROOT_DIR}/VERSION.txt" SWT_TESTING_LIBRARY_VERSION LIMIT_COUNT 1)
 if(SWT_TESTING_LIBRARY_VERSION)