🥺 Hard to debug/develop SwiftFoundation

YOCKOW · July 22, 2022, 1:02am

Once upon a time, we were able to develop SwiftFoundation only with Xcode, latest toolchain, swift-corelibs-xctest repo, and swift-corelibs-foundation repo.
Nowadays, we can't do so because:

SR-12177 hinders our using latest toolchain to run TestFoundation.
Xcode's default toolchain lacks some(all?) SPIs and can't compile SwiftFoundation. (For example, "Cannot find '_forEachField' in scope" errors occur because @_spi(Reflection) import Swift imports no SPI symbols.)
- Foundation overlay can't be compiled with default toolchain because of the same reason.
TestFoundation can't be compiled with any toolchain using Xcode which tries to load duplicately modulemaps of CoreFoundation. [Forum topic #50360] [GitHub issue #4608]

Thus we must checkout swift repo and related repos and run 'swift/utils/build-script' to test SwiftFoundation.
How do we regain the past condition?
I have no idea.

Tony_Parker · July 25, 2022, 4:06pm

I haven't had the chance to try it myself yet, but do you think the improvements in Swift 5.7 for module aliasing could help with the CoreFoundation import issue?

github.com

apple/swift-evolution/blob/main/proposals/0339-module-aliasing-for-disambiguation.md

# Module Aliasing For Disambiguation

* Proposal: [SE-0339](0339-module-aliasing-for-disambiguation.md)
* Authors: [Ellie Shin](https://github.com/elsh)
* Review Manager: [John McCall](https://github.com/rjmccall)
* Status: **Implemented (Swift 5.7)** 
* Pitch: [Module Aliasing](https://forums.swift.org/t/pitch-module-aliasing/51737)
* Implementation: ([toolchain](https://github.com/apple/swift/pull/40899)),
[apple/swift-package-manager#4023](https://github.com/apple/swift-package-manager/pull/4023), others
* Review: ([review](https://forums.swift.org/t/se-0339-module-aliasing-for-disambiguation/54730)) ([acceptance](https://forums.swift.org/t/accepted-with-modifications-se-0339-module-aliasing-for-disambiguation/55032))

## Introduction

Swift does not allow multiple modules in a program to share the same name, and attempts to do so will fail to build. These name collisions can happen in a reasonable program when using multiple packages developed independently from each other. This proposal introduces a way to resolve these conflicts without making major, invasive changes to a package's source by turning a module name in source into an alias, a different unique name.

## Motivation

As the Swift package ecosystem has grown, programmers have begun to frequently encounter module name clashes, as seen in several forum discussions including [module name 'Logging' clash in Vapor](https://forums.swift.org/t/logging-module-name-clash-in-vapor-3/25466) and [namespacing packages/modules regarding SwiftNIO](https://forums.swift.org/t/namespacing-of-packages-modules-especially-regarding-swiftnio/24726). There are two main use cases where these arise:

* Two different packages include logically different modules that happen to have the same name.  Often, these modules are "internal" dependencies of the package, which would be submodules if Swift supported submodules; for example, it's common to put common utilities into a `Utils` module, which will then collide if more than one package does it.  Programmers often run into this problem when adding a new dependency or upgrading an existing one.

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For the _forEachField thing, I think the ultimate resolution is to find a way to get reflection to be a first class Swift feature. AttributedString needs to use it to get the API surface we wanted, unfortunately.

YOCKOW · July 27, 2022, 8:12am

IIUC, CoreFoundation is a simple clang module that is not supported by SE-0339, isn't it?

Only pure Swift modules allowed for aliasing: no ObjC/C/C++/Asm due to potential symbol collision.

I agree.
However, as mentioned above, the overlay also requires @_spi feature, so that the problem is more general.

Fidetro · July 30, 2022, 5:44pm

I've been trying to debug SwiftFoundation recently and have run into the same problem.
I'm trying other ways to debug SwiftFoundation,actually not ideal.
Can you tell me more about "Thus we must checkout swift repo and related repos and run 'swift/utils/build-script' to test SwiftFoundation."?
Thanks

YOCKOW · August 1, 2022, 3:47am

Sorry, but I think I should have added "on Linux" to that sentence...
'build-script' seems not to build TestFoundation on macOS.

Fidetro · August 4, 2022, 6:31pm

I'm disappointed that it looks like the problem of not being able to compile with Xcode has been around for a long time,And I don't see any official Apple developers providing us with answers or working on solutions.

vidugloeck · March 26, 2023, 7:18am

I am encountering the same issue. Is there currently any way to run TestFoundation in Xcode?
Any help would be much appreciated.

ahs1 · April 18, 2024, 8:50am

Same issue here. Hard to understand that compiling such base of swift is so hard on the preferred platform [macOS] for this language.