Direction and Scope

[nanotech]

The first choice to make for the direction of the tutorial is whether to let GHC or swiftc build the final executable. I chose to let Xcode and swiftc build the executable, but having GHC link to a Swift framework might be a good choice too. Reasons to embed the Haskell library include

• GHC linking will probably change less than Swift in the future. Swift is likely to change as its ABI story progresses.
• Xcode automatically bundles the right Swift dylibs for you.
• Xcode is always updated with all app bundle features (icons, signing, Info.plist editor).
• Xcode knows exactly how all the Swift code is built and can provide correct code completion and debugging.
• If Haskell is being used as a backend for a Swift frontend, being able to directly call into linked Haskell functions is probably more useful than the reverse.
• I've embedded Haskell libraries before.

Reasons not to:

• Dynamic library dependencies need to be chased and copied to the bundle. If GHC builds the executable, it can link them all statically. This is solvable with tooling like cabal-macosx.
• Haskell can't call directly into the app's Swift functions by linking. (Although it can still call system frameworks.)

The Xcode project currently includes stack build as a build script phase, but this could be inverted by having Setup.hs call xcodebuild.

The tutorial currently only covers passing integers from Swift to Haskell, but I'd like to also cover passing bytestrings and functions in both directions.

[biglambda]

Ok, I'm having trouble giving you a good recommendation here. I was in fact expecting the first option because in my case most of the development happens on the Haskell side, I don't expect to be calling a lot of Swift functions from Haskell.

[nanotech]

Yes, I do think going Swift -> Haskell is generally the better option, but wanted to document some reasons why the other way could or couldn't work too.

[biglambda]

I mean I think if you can make it work or explain the issue well, that's useful.

[biglambda]

Sorry for the delay. Attempting to go through the tutorial and so far when I get to the build after setting up runNSApplication. I get the following:
biglambda$ stack build
CruxLibrary-0.1.0.0: build
Preprocessing executable 'Crux' for CruxLibrary-0.1.0.0...
Linking .stack-work/dist/x86_64-osx/Cabal-1.24.2.0/build/Crux/Crux ...
ld: framework not found CruxLibrary
clang: error: linker command failed with exit code 1 (use -v to see invocation)
gcc' failed in phase Linker'. (Exit code: 1)

-- While building package CruxLibrary-0.1.0.0 using:
/Users/biglambda/.stack/setup-exe-cache/x86_64-osx/setup-Simple-Cabal-1.24.2.0-ghc-8.0.2 --builddir=.stack-work/dist/x86_64-osx/Cabal-1.24.2.0 build exe:Crux --ghc-options " -ddump-hi -ddump-to-file"
Process exited with code: ExitFailure 1

Not sure where to place the framework. My directory structure is the same as yours I think.

[nanotech]

I did forget to mention to build the framework at the end of the Converting the Swift App to a Framework section, so you might just need to build the framework in Xcode before stack building. I've added that in now.

The framework should be symlinked to its location in the Xcode build directory from the project's build/ directory. The symlink should be created by the Run Script phase added at the end of the Converting the Swift App to a Framework section.

Here's what's in my project's build directory after a successful build:

# tree -a build
build
├── SwiftAppLibrary.framework -> /Users/nanotech/Library/Developer/Xcode/DerivedData/SwiftHaskell-cwfykomvmcuamcbfwulxhcfjpbdi/Build/Products/Debug/SwiftAppLibrary.framework
├── SwiftHaskell -> ../.stack-work/dist/x86_64-osx/Cabal-1.24.0.0/build/SwiftHaskell/SwiftHaskell
└── ghc
    └── include -> /Users/nanotech/.stack/programs/x86_64-osx/ghc-8.0.1/bin/../lib/ghc-8.0.1/include

3 directories, 1 file

[biglambda]

Sorry for this, I'm pretty new to XCode, I haven't been able to build the framework, getting some strange errors in XCode:

-- file:///Users/biglambda/Software/crux/xcode/.DS_Store: warning: Missing file: /Users/biglambda/Software/crux/xcode/.DS_Store is missing from working copy

-- PBXCp build/Crux /Users/biglambda/Library/Developer/Xcode/DerivedData/Crux-henfnnwgwlypjocyelgjcuwrmuzb/Build/Products/Debug/CruxLibrary.framework/Versions/A/Crux
cd /Users/biglambda/Software/crux/xcode/Crux
builtin-copy -exclude .DS_Store -exclude CVS -exclude .svn -exclude .git -exclude .hg -resolve-src-symlinks /Users/biglambda/Software/crux/xcode/Crux/build/Crux /Users/biglambda/Library/Developer/Xcode/DerivedData/Crux-henfnnwgwlypjocyelgjcuwrmuzb/Build/Products/Debug/CruxLibrary.framework/Versions/A

error: /Users/biglambda/Software/crux/xcode/Crux/build/../.stack-work/dist/x86_64-osx/Cabal-1.24.2.0/build/Crux/Crux: No such file or directory

[nanotech]

-- file:///Users/biglambda/Software/crux/xcode/.DS_Store: warning: Missing file: /Users/biglambda/Software/crux/xcode/.DS_Store is missing from working copy

A crux/xcode/.DS_Store Finder display settings file was staged into git and then deleted from the working copy. I think running git rm crux/xcode/.DS_Store should clear this up. For the future, add .DS_Store to your global gitignore (at ~/.config/git/ignore by default).

-- PBXCp build/Crux ... No such file or directory

Xcode is trying to copy the Haskell executable into the app bundle here, but it isn't built yet. You don't need to build the app bundle yet though, just the framework, so set the framework as the current target before building:

The tutorial describes the build ordering a bit later in the middle of Linking to the Executable.

[biglambda]

That doesn't seem to solve the "PBXCp build/Crux ... No such file or directory" error.

It says in the tutorial to make SwiftAppLibrary the only target of AppDelegate.swift and MainMenu.xib. It seems greyed out for AppDelegate.swift

[nanotech]

Can you check the Build Phases of the two targets? Target membership checkboxes can be greyed out if a Compile Sources phase is missing. For the framework, they should be

• Target Dependencies
  • (empty)
• Run Script (optional)
  • stack build; bash link-deps.sh
  • (Input/output files don't matter for this issue)
• Compile Sources
  • AppDelegate.swift (Source files can also be added to targets from here)
  • SwiftAppLibrary.m
• Link Binary With Libraries
  • (empty)
• Headers
  • Public: SwiftAppLibrary.h
  • Others: (empty)
• Copy Bundle Resources
  • MainMenu.xib
• Run Script
  • set -u; ln -sf "${BUILT_PRODUCTS_DIR}/${FULL_PRODUCT_NAME}" "${PROJECT_DIR}/build/"

For the app bundle,

• Target Dependencies
  • SwiftAppLibrary
• Copy Bundle Resources
  • Assets.xcassets
• Embed Frameworks
  • Destination: Frameworks
  • SwiftAppLibrary.framework
• Copy Files
  • Destination: Executables
  • SwiftHaskell

Substitute SwiftHaskell and SwiftAppLibrary with your Haskell executable and Swift framework names respectively.

The only time Xcode should be copying from build/../.stack-work/dist/x86_64-osx/Cabal-1.24.2.0/build/Crux/Crux is in the last Copy Files phase of the app bundle target.

[biglambda]

Ok the library builds properly but the app still gives:

Unable to run command 'PBXCp Crux.app' - this target might include its own product.
Unable to run command 'ValidateEmbeddedBinary Crux.app' - this target might include its own product.
Unable to run command 'Touch Crux.app' - this target might include its own product.
Unable to run command 'CodeSign Crux.app' - this target might include its own product.
Unable to run command 'RegisterWithLaunchServices Crux.app' - this target might include its own product.

[nanotech]

this target might include its own product

Is the app's Executable Copy Files phase perhaps set to copy Crux.app (the built app bundle and product of the app target) instead of build/Crux (the Haskell executable)?

[biglambda]

Ok, seems to be building but crashes:

dyld: Library not loaded: @rpath/libswiftAppKit.dylib
Referenced from: /Users/biglambda/Library/Developer/Xcode/DerivedData/Crux-henfnnwgwlypjocyelgjcuwrmuzb/Build/Products/Debug/CruxLibrary.framework/Versions/A/CruxLibrary
Reason: image not found
(lldb)

Here's the build phases:
http://imgur.com/mcGGB8R

[nanotech]

In the framework target's Build Settings, is Always Embed Swift Standard Libraries set to Yes?

Your build phases all look correct.

Here's the contents of the tutorial project's compiled app:

$ tree -a SwiftHaskell.app
SwiftHaskell.app
└── Contents
    ├── Frameworks
    │   └── SwiftAppLibrary.framework
    │       ├── Resources -> Versions/Current/Resources
    │       ├── SwiftAppLibrary -> Versions/Current/SwiftAppLibrary
    │       └── Versions
    │           ├── A
    │           │   ├── Frameworks
    │           │   │   ├── libswiftAppKit.dylib
    │           │   │   ├── libswiftCore.dylib
    │           │   │   ├── libswiftCoreData.dylib
    │           │   │   ├── libswiftCoreGraphics.dylib
    │           │   │   ├── libswiftCoreImage.dylib
    │           │   │   ├── libswiftDarwin.dylib
    │           │   │   ├── libswiftDispatch.dylib
    │           │   │   ├── libswiftFoundation.dylib
    │           │   │   ├── libswiftIOKit.dylib
    │           │   │   ├── libswiftObjectiveC.dylib
    │           │   │   ├── libswiftQuartzCore.dylib
    │           │   │   ├── libswiftSwiftOnoneSupport.dylib
    │           │   │   └── libswiftXPC.dylib
    │           │   ├── Resources
    │           │   │   ├── Base.lproj
    │           │   │   │   └── MainMenu.nib
    │           │   │   ├── Info.plist
    │           │   │   └── libswiftRemoteMirror.dylib
    │           │   ├── SwiftAppLibrary
    │           │   └── _CodeSignature
    │           │       └── CodeResources
    │           └── Current -> A
    ├── Info.plist
    ├── MacOS
    │   └── SwiftHaskell
    ├── PkgInfo
    ├── Resources
    └── _CodeSignature
        └── CodeResources

14 directories, 23 files

[biglambda]

Ok it was set to no. It's running now and showing the window. I'll go through the rest tonight and we can finish up the bounty.
Basically all I think should happen to complete the tutorial is a little more explanation of why. Assume most haskellers have zero knowledge of Xcode or this method of linking so:

-- Each symlink you've created in your shell script should have an explanation of it's purpose.
-- More explanation of why you chose the various settings in XCode.
-- Links to further understanding in Apple documentation, books or elsewhere. Show us how to get this specialization.
-- Include all of the information from this troubleshooting thread in the tutorial.
-- Also you should submit a pull request to Daniel the cabal-macosx maintainer if you haven't already.

Great work and thanks.

[biglambda]

Also I didn't quite use the same names as you did. When you "import SwiftHaskell" in your AppDelegate.swift, to which file are you referring? I see, it's in the module.modulemap file. Why would I get a AppDelegate.swift:20:32: Use of unresolved identifier 'square'

http://imgur.com/7Aso88N