Change Args file format from multiline to shell

[keith]

With the shell file format arguments on each line are quoted, which
makes these use cases compatible with files with spaces in their paths.

[keith]

So I actually found a problem with this a little further down the chain. Setting this results in this flag being wrapped in quotes '-DDEBUG=1' which ends up making clang assume this is a file path, resulting in an error because a swift frontend invocation attempts to exec clang only once, but it ends up assuming 2 files need to be handled. I'm not exactly sure what the workaround is here.

[keith]

The specific clang command (found using -Xfrontend -dump-clang-diagnostics is:

'clang' '-fsyntax-only' '-fblocks' '-D__swift__=40200' '-fretain-comments-from-system-headers' '-isystem' '/Applications/Xcode-10.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift' '-fPIC' '-fmodules' '-Xclang' '-fmodule-feature' '-Xclang' 'swift' '-Werror=non-modular-include-in-framework-module' '-x' 'objective-c' '-std=gnu11' '-fobjc-arc' '-DSWIFT_CLASS_EXTRA=__attribute__((annotate("__swift native")))' '-DSWIFT_PROTOCOL_EXTRA=__attribute__((annotate("__swift native")))' '-DSWIFT_EXTENSION_EXTRA=__attribute__((annotate("__swift native")))' '-DSWIFT_ENUM_EXTRA=__attribute__((annotate("__swift native")))' '-D_ISO646_H_' '-D__ISO646_H' '-DSWIFT_SDK_OVERLAY_APPKIT_EPOCH=2' '-DSWIFT_SDK_OVERLAY_FOUNDATION_EPOCH=8' '-DSWIFT_SDK_OVERLAY2_SCENEKIT_EPOCH=3' '-DSWIFT_SDK_OVERLAY_GAMEPLAYKIT_EPOCH=1' '-DSWIFT_SDK_OVERLAY_SPRITEKIT_EPOCH=1' '-DSWIFT_SDK_OVERLAY_COREIMAGE_EPOCH=2' '-DSWIFT_SDK_OVERLAY_DISPATCH_EPOCH=2' '-DSWIFT_SDK_OVERLAY_PTHREAD_EPOCH=1' '-DSWIFT_SDK_OVERLAY_COREGRAPHICS_EPOCH=0' '-DSWIFT_SDK_OVERLAY_UIKIT_EPOCH=2' '-D__SWIFT_COMPILER_VERSION=1000037001000' '-isysroot' '/Applications/Xcode-10.0.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator12.0.sdk' '-fmodules-validate-system-headers' '-Xclang' '-fmodule-format=obj' '-fapinotes-modules' '-iapinotes-modules' '/Applications/Xcode-10.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift/iphonesimulator/x86_64' '-fapinotes-swift-version=4.2' '-target' 'x86_64-apple-ios10.0' '<swift-imported-modules>' '-resource-dir' '/Applications/Xcode-10.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift/clang' '-working-directory' '/private/var/tmp/_bazel_ksmiley/0b4aec06d0a277d8a5aa9cd2752bc453/execroot/__main__' '-v' '-iquotebazel-out/darwin-fastbuild/genfiles' '-iquote.' '-O0' ''-DDEBUG=1''

Which results in this error:

<unknown>:0: error: unable to handle compilation, expected exactly one compiler job in
...
<unknown>:0: error: clang importer creation failed

Because both ''-DDEBUG=1'' and <swift-imported-modules> create invocations to clang from the frontend

[keith]

I am able to workaround this by setting experimental_objc_fastbuild_options to nothing, since that's where the debug flag is coming from https://github.com/bazelbuild/bazel/blob/d65ed23beb4b97c6b33eb7d625f98da7e0893b58/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcCommandLineOptions.java#L140-L141

[keith]

Thinking more about this, this might be because of how we're forwarding the arguments to python's check_output. Because this only happens when going through our WIP persistent worker. I'll investigate further

[keith]

It actually looks like libtool handles spaces in file paths in these files, so quoting it is redundant and invalid. To be safe I think I'll change this to only quote the Swift place as long as this builds otherwise