Linux Build Broken on Swift 5.3+: kCFStringEncodingUTF8 not in scope

[xanderdunn]

Added to Package.swift:

.package(name: "OpenCombine",
    url: "https://github.com/OpenCombine/OpenCombine.git",
    from: "0.10.0")

// Added to target dependencies:
.product(name: "OpenCombine", package: "OpenCombine"),
.product(name: "OpenCombineDispatch", package: "OpenCombine"),
.product(name: "OpenCombineFoundation", package: "OpenCombine"),

On macOS 10.15.6 using Swift for Tensorflow v0.11 I am able to build successfully:

$ which swift
/Library/Developer/Toolchains/swift-tensorflow-RELEASE-0.11.xctoolchain/usr/bin/swift
$ swift --version
Swift version 5.3-dev (LLVM db8896f3f345af2, Swift 61684f62a6132c0)
Target: x86_64-apple-darwin19.6.0

However, on Ubuntu 18.04 using Swift for Tensorflow v0.10 I am unable to build successfully:

$ which swift
/home/xander/swift-tensorflow-RELEASE-0.10-cuda10.2-cudnn7-ubuntu18.04/usr/bin/swift
$ swift --version
Swift version 5.3-dev (LLVM 55d27a5828, Swift 6a5d84ec08)
Target: x86_64-unknown-linux-gnu
$ swift build
.build/checkouts/OpenCombine/Sources/OpenCombineFoundation/Timer+Publisher.swift:343:34: error: cannot find 'kCFStringEncodingUTF8' in scope
                CFStringEncoding(kCFStringEncodingUTF8)
                                 ^~~~~~~~~~~~~~~~~~~~~

Swift for Tensorflow is based on the official dev branch.

I also tried building on the latest official 5.3 release branch on Ubuntu 18.04, still same error:

$ which swift
/home/xander/swift-5.3-DEVELOPMENT-SNAPSHOT-2020-08-31-a-ubuntu18.04/usr/bin/swift
$ swift --version
Swift version 5.3-dev (LLVM 3fa9679add, Swift d24649a4d6)
Target: x86_64-unknown-linux-gnu
$ swift build
.build/checkouts/OpenCombine/Sources/OpenCombineFoundation/Timer+Publisher.swift:343:34: error: cannot find 'kCFStringEncodingUTF8' in scope
                CFStringEncoding(kCFStringEncodingUTF8)
                                 ^~~~~~~~~~~~~~~~~~~~~

However, I can successfully build on Ubuntu 18.04 with Swift 5.2.5 official release toolchain:

$ which swift
/home/xander/swift-5.2.5-RELEASE-ubuntu18.04/usr/bin/swift
$ swift --version
Swift version 5.2.5 (swift-5.2.5-RELEASE)
Target: x86_64-unknown-linux-gnu

It appears specifically on Linux, the build is broken on Swift 5.3 release branch, as well as dev trunk.

Strangely, I do see kCFStringEncodingUTF8 referenced in the swift-corelibs-foundation. Is there an additional #include that's required now?

[broadwaylamb]

Hello!

Could you please try building from the master branch?

.package(name: "OpenCombine",
    url: "https://github.com/OpenCombine/OpenCombine.git",
    .branch("master"))

The issue should have been fixed in #173.

[xanderdunn]

Oh yeah, that resolves it, thanks! Should've thought to try off master.

I searched the issues for kCFStringEncodingUTF8 and didn't see anything, but I didn't search the pull requests!