Unconditionally conform Attachment to CustomStringConvertible.

grynspan · grynspan · commit 04a26d311987 · 2025-09-26T23:48:42.000-04:00
This PR adjusts `Attachment`'s conformance to `CustomStringConvertible`
such that it conforms even when `AttachableValue` is not `Copyable`. We
now check at runtime (by way of protocol shenanigans, of course) whether
the attachable value is copyable and, if so, take a different code path
than we take if it does not conform.
diff --git a/Sources/Testing/Attachments/Attachment.swift b/Sources/Testing/Attachments/Attachment.swift
@@ -97,6 +97,19 @@ public struct Attachment<AttachableValue> where AttachableValue: Attachable & ~C
 extension Attachment: Sendable where AttachableValue: Sendable {}
 extension Attachment.Storage: Sendable where AttachableValue: Sendable {}
 
+#if !hasFeature(Embedded)
+/// A protocol that describes an attachment with a copyable value.
+///
+/// We can use this protocol to make runtime decisions about attachments based
+/// on whether or not their attachable values are copyable.
+private protocol _AttachmentWithCopyableValue {
+  associatedtype AttachableValue: Attachable & Copyable
+  var attachableValue: AttachableValue { get }
+}
+
+extension Attachment: _AttachmentWithCopyableValue where AttachableValue: Copyable {}
+#endif
+
 // MARK: - Initializing an attachment
 
 extension Attachment where AttachableValue: ~Copyable {
@@ -180,21 +193,19 @@ public struct AnyAttachable: AttachableWrapper, Sendable, Copyable {
 
 // MARK: - Describing an attachment
 
-extension Attachment where AttachableValue: ~Copyable {
-  @_documentation(visibility: private)
-  public var description: String {
-    let typeInfo = TypeInfo(describing: AttachableValue.self)
-    return #""\#(preferredName)": instance of '\#(typeInfo.unqualifiedName)'"#
-  }
-}
-
-extension Attachment: CustomStringConvertible {
+extension Attachment: CustomStringConvertible where AttachableValue: ~Copyable {
   /// @Metadata {
   ///   @Available(Swift, introduced: 6.2)
   ///   @Available(Xcode, introduced: 26.0)
   /// }
   public var description: String {
-    #""\#(preferredName)": \#(String(describingForTest: attachableValue))"#
+#if !hasFeature(Embedded)
+    if let selfCopy = self as? any _AttachmentWithCopyableValue {
+      return #""\#(preferredName)": \#(String(describingForTest: selfCopy.attachableValue))"#
+    }
+#endif
+    let typeInfo = TypeInfo(describing: AttachableValue.self)
+    return #""\#(preferredName)": instance of '\#(typeInfo.unqualifiedName)'"#
   }
 }
 
diff --git a/Tests/TestingTests/AttachmentTests.swift b/Tests/TestingTests/AttachmentTests.swift
@@ -50,15 +50,15 @@ struct AttachmentTests {
     let attachableValue = MySendableAttachable(string: "<!doctype html>")
     let attachment = Attachment(attachableValue, named: "AttachmentTests.saveValue.html")
     #expect(String(describing: attachment).contains(#""\#(attachment.preferredName)""#))
-    #expect(attachment.description.contains("MySendableAttachable("))
+    #expect(String(describing: attachment).contains("MySendableAttachable("))
   }
 
 #if compiler(>=6.3) || !os(Windows) // WORKAROUND: swift-#84184
   @Test func moveOnlyDescription() {
     let attachableValue = MyAttachable(string: "<!doctype html>")
     let attachment = Attachment(attachableValue, named: "AttachmentTests.saveValue.html")
-    #expect(attachment.description.contains(#""\#(attachment.preferredName)""#))
-    #expect(attachment.description.contains("'MyAttachable'"))
+    #expect(String(describing: attachment).contains(#""\#(attachment.preferredName)""#))
+    #expect(String(describing: attachment).contains("'MyAttachable'"))
   }
 #endif
 
