MetaCodable

Forked from SwiftyLab/MetaCodable. Context at swift-collections-archive-failure-mac-catalyst.

swift-collections/MetaCodable MacCatalyst archive failure

MetaCodable's import of swift-collections MacCatalyst archive build to fail with the following error on Xcode 16 RC1 and 16.1 beta, building in Swift 5 language mode.

Showing All Errors Only
Prepare build
error: Multiple commands produce '/Users/adamz/Developer/voidapp/void/DerivedData/Void/Build/Intermediates.noindex/ArchiveIntermediates/Void/IntermediateBuildFilesPath/UninstalledProducts/macosx/InternalCollectionsUtilities.o'
    note: Target 'InternalCollectionsUtilities' (project 'swift-collections') has a command with output '/Users/adamz/Developer/voidapp/void/DerivedData/Void/Build/Intermediates.noindex/ArchiveIntermediates/Void/IntermediateBuildFilesPath/UninstalledProducts/macosx/InternalCollectionsUtilities.o'

>     note: Target 'InternalCollectionsUtilities' (project 'swift-collections') has a command with output '/Users/adamz/Developer/voidapp/void/DerivedData/Void/Build/Intermediates.noindex/ArchiveIntermediates/Void/IntermediateBuildFilesPath/UninstalledProducts/macosx/InternalCollectionsUtilities.o'
> error: Multiple commands produce '/Users/adamz/Developer/voidapp/void/DerivedData/Void/Build/Intermediates.noindex/ArchiveIntermediates/Void/IntermediateBuildFilesPath/UninstalledProducts/macosx/OrderedCollections.o'

note: Target 'OrderedCollections' (project 'swift-collections') has a command with output '/Users/adamz/Developer/voidapp/void/DerivedData/Void/Build/Intermediates.noindex/ArchiveIntermediates/Void/IntermediateBuildFilesPath/UninstalledProducts/macosx/OrderedCollections.o'

>     note: Target 'OrderedCollections' (project 'swift-collections') has a command with output '/Users/adamz/Developer/voidapp/void/DerivedData/Void/Build/Intermediates.noindex/ArchiveIntermediates/Void/IntermediateBuildFilesPath/UninstalledProducts/macosx/OrderedCollections.o'
> Multiple commands produce '/Users/adamz/Developer/voidapp/void/DerivedData/Void/Build/Intermediates.noindex/ArchiveIntermediates/Void/IntermediateBuildFilesPath/UninstalledProducts/macosx/InternalCollectionsUtilities.o'

Multiple commands produce '/Users/adamz/Developer/voidapp/void/DerivedData/Void/Build/Intermediates.noindex/ArchiveIntermediates/Void/IntermediateBuildFilesPath/UninstalledProducts/macosx/OrderedCollections.o' Build failed 9/16/24, 00:46 1.3 seconds

## Issues
Root cause unknown. An Xcode build fails to deduplicate `MetaCodable`'s `swift-collections` symbols with those imported by other targets in the repo.
## Fix
In this reproduction repo the archival failure is fixed by:
* Copying `MetaCodable` into a dedicated local SPM package.
* Copying the parts of `swift-collections` used by `MetaCodable` into its SPM package.
* Renaming the copied `InternalCollectionsUtilities` and `OrderedCollections` targets with an `MC` prefix to prevent package graph conflicts.
* Replacing occurrences of the renamed symbols with their updates.
* Resolving warnings about the unsafe runtime use of `@_implementationOnly` in the copied `swift-collections` files (`OrderedCollections` when importing `InternalCollectionsUtilities`) by removing their use and using plain imports.
The issue and fix can be reproduced by swapping from/to the local version of `MetaCodable` in this repo's `Package.swift`.