Ability to set Xcode build flags

[elihwyma]

Currently I don't see anyway to set Xcode build flags in a .spi.yml configuration file. This means that packages that include C++ code, and would need the SWIFT_OBJC_INTEROP_MODE = objcxx; Xcode variable will not build from Xcode. An example package is PugiSwift

[finestructure]

How do you currently pass this parameter to your build command? I would expect it to be either via build settings in Package.swift or via a setting in you scheme in your xcodeproj or xcconfig file.

[elihwyma]

This is a bit of an annoyance with Swift, you have to specify the flag in both your xcodeproj and Package.swift file. Currently it will build fine with swift build but if you do it through Xcode it will fail unless you add the flag. Does the build system use a .xcconfig file already?

[elihwyma]

Ha I found the bug, apologies 🥲

[elihwyma]

Reopening this as I found the exact issue. The build command setting the OTHER_SWIFT_FLAGS causes the Swift flags in the Package.swift to be ignored, so the custom flag required (C++ Interop) is ignored causing the compile to fail.

[finestructure]

Could you point me to a failing build to get a better understanding what the setup looks like and what our build command is?

[elihwyma]

Sure, this build that uses Xcode for macOS fails whereas this build succeeds.

[finestructure]

For later reference (because the builds will eventually disappear) this is about the package PugiSwift.

Thanks for those links, @elihwyma . I see and can reproduce the issue now. Unfortunately, I don't think that's something that's easy to fix. I've run a test to try and preserve the setting while also adding the Swift 6 flags we're injecting but that test was unsuccessful.

Note that the injection of OTHER_SWIFT_FLAGS for xcodebuild builds is something we will only be doing while we are running the Ready for Swift 6 project tracking Swift 6 adoption. While we don't have an exact timeline in mind when we'll stop running these "special" builds, it's not something we plan on doing permanently.

That said, I wanted to note that the reported build matrix on your package page would not actually change at all if this xcodebuild passed. Here's what it looks like right now:

You'll notice that we show both Swift 6 and macOS compatibility and that's due to the way we aggregate the individual results up. The passing SwiftPM build ensures that your package gets credit for this combination and the failing xcodebuild doesn't enter the picture.

Does that work for your package in the interim?

[elihwyma]

The only part of the matrix I would like to have "changed" is the platform support. It should be usable on every platform. The Swift 6.0 only is because I use some of the new syntax.