Avoid eagerly serializing move-only attachments. #1317
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This PR adjusts the interface of `Attachment` so that it always conforms to `Copyable` even if the value it wraps does not. This allows us to avoid eagerly serializing attachments that are not `Copyable` but _are_ `Sendable`. We must still eagerly serialize non-sendable attachments. This change will allow us to support "attachment lifetime" (API to be designed, see XCTest's API [here](https://developer.apple.com/documentation/xctest/xctattachment/lifetime-swift.enum)) more efficiently and for more attachable values. If you're paying the cost of serialization for attachments you don't end up keeping, that's a waste of\ resources.
grynspan
requested review from
briancroom,
suzannaratcliff and
jerryjrchen
as code owners
grynspan
added
concurrency
stmontgomery
approved these changes
Sep 15, 2025
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This PR adjusts the interface of
Attachmentso that it always conforms toCopyableeven if the value it wraps does not. This allows us to avoid eagerly serializing attachments that are notCopyablebut areSendable. We must still eagerly serialize non-sendable attachments.This change will allow us to support "attachment lifetime" (API to be designed, see XCTest's API here) more efficiently and for more attachable values. If you're paying the cost of serialization for attachments you don't end up keeping, that's a waste of\ resources.
Checklist: