从Package.swift运行shell脚本

Question

I'm trying to include a hardcoded version string generated by git describe within a CLI I'm writing in Swift.

The idea was to have a shell script that executes git describe and writes that as a global constant into a file called Version.swift , which I can then reference from within my tool.

I don't want to have to think about running this script before every build though or building the project via another shell script. The ideal way would be to keep using swift build and having Swift itself invoke said script when it compiles and evaluates Package.swift .

So I included the following in my package manifest.

import Foundation

let task = Process()
task.launchPath = "./"
task.arguments = ["update_version.sh"]
task.launch()
task.waitUntilExit()

Whilst importing Foundation and initializing the task seems to work just fine, actually launching it crashes and outputs the following stack trace.

error: manifest parse error(s):
2017-07-28 15:07:43.711 swift[39828:16163314] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Couldn't posix_spawn: error 13'
*** First throw call stack:
(
    0   CoreFoundation                      0x00007fff9be232cb __exceptionPreprocess + 171
    1   libobjc.A.dylib                     0x00007fffb0c5d48d objc_exception_throw + 48
    2   CoreFoundation                      0x00007fff9bea1c3d +[NSException raise:format:] + 205
    3   Foundation                          0x00007fff9d84c54e -[NSConcreteTask launchWithDictionary:] + 3134
    4   ???                                 0x0000000109ccb1c3 0x0 + 4459377091
    5   swift                               0x00000001045fe84f _ZN4llvm5MCJIT11runFunctionEPNS_8FunctionENS_8ArrayRefINS_12GenericValueEEE + 655
    6   swift                               0x0000000104604ab3 _ZN4llvm15ExecutionEngine17runFunctionAsMainEPNS_8FunctionERKNSt3__16vectorINS3_12basic_stringIcNS3_11char_traitsIcEENS3_9allocatorIcEEEENS8_ISA_EEEEPKPKc + 707
    7   swift                               0x00000001039f4512 _ZL14performCompileRN5swift16CompilerInstanceERNS_18CompilerInvocationEN4llvm8ArrayRefIPKcEERiPNS_16FrontendObserverEPNS_20UnifiedStatsReporterE + 22802
    8   swift                               0x00000001039ed394 _ZN5swift15performFrontendEN4llvm8ArrayRefIPKcEES3_PvPNS_16FrontendObserverE + 7332
    9   swift                               0x00000001039a2ad8 main + 12248
    10  libdyld.dylib                       0x00007fffb1542235 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
0  swift                    0x0000000107073eaa PrintStackTraceSignalHandler(void*) + 42
1  swift                    0x00000001070732e6 SignalHandler(int) + 662
2  libsystem_platform.dylib 0x00007fffb1751b3a _sigtramp + 26
3  libsystem_platform.dylib 0x00000003ba442240 _sigtramp + 147785504
4  libsystem_c.dylib        0x00007fffb15d6420 abort + 129
5  libc++abi.dylib          0x00007fffb012c84a __cxa_bad_cast + 0
6  libc++abi.dylib          0x00007fffb0151c4f default_unexpected_handler() + 0
7  libobjc.A.dylib          0x00007fffb0c5f6fe _objc_terminate() + 103
8  libc++abi.dylib          0x00007fffb014ed69 std::__terminate(void (*)()) + 8
9  libc++abi.dylib          0x00007fffb014e9f2 __cxa_rethrow + 99
10 libobjc.A.dylib          0x00007fffb0c5d94a objc_exception_rethrow + 40
11 Foundation               0x00007fff9d84c884 -[NSConcreteTask launchWithDictionary:] + 3956
12 Foundation               0x0000000109ccb1c3 -[NSConcreteTask launchWithDictionary:] + 1816656051
13 swift                    0x00000001045fe84f llvm::MCJIT::runFunction(llvm::Function*, llvm::ArrayRef<llvm::GenericValue>) + 655
14 swift                    0x0000000104604ab3 llvm::ExecutionEngine::runFunctionAsMain(llvm::Function*, std::__1::vector<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > > const&, char const* const*) + 707
15 swift                    0x00000001039f4512 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) + 22802
16 swift                    0x00000001039ed394 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 7332
17 swift                    0x00000001039a2ad8 main + 12248
18 libdyld.dylib            0x00007fffb1542235 start + 1
Stack dump:
0.  Program arguments: /Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift -frontend -interpret /Users/kilian/dev/apodidae/Package.swift -target x86_64-apple-macosx10.10 -enable-objc-interop -sdk /Applications/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk -I /Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift/pm/4 -swift-version 4 -module-name Package -lPackageDescription -- -fileno 5

The content of update_version.sh is the following

echo "// THIS FILE IS AUTO-GENERATED\npublic let VERSION = \""$(git describe)"\"" > Sources/target/Version.swift

What could I do here to get this to work? Does this have to do with the package manifest being executed within a sandbox? And if so, what options do I have to accomplish what I'm trying to do? If in any way possible I'd really love to just run swift build and have the rest just work .

Answer 1

the exception has NOTHING with your approach, the system raised it because your launchPath is NOT a valid launch path :-). You have to be ABSOLUTELY sure about the validity of your launchPath, otherwise, the execution will be terminated with some uncaught exception. For a solution see how to solve it