Including Swift Package deal Supervisor Help – Half 2

Within the earlier put up I checked out among the historical past of how we packaged up our library code to be used by our fellow builders. We checked out among the advantages of static libraries versus dynamic frameworks which additionally include headers wanted by the integrator.

Now let’s dive into the steps that had been crucial for me to allow SPM help on the primary few libraries DTCoreText, DTFoundation and Kvitto. It took me a number of days to iron out all of the kinks and I’d like to share with you what I discovered within the course of.

We’re used to utilizing Xcode to explain what goes right into a construct: Which information to compile, what exterior libraries to hyperlink to, what assets are wanted and likewise normal construct settings just like the vary and forms of supported platforms. Extra exactly, these settings are contained within the undertaking.pbxproj file inside your xcodeproj bundle.

With SwiftPM there isn’t any such undertaking file. Somewhat the whole lot is outlined in human-readable type within the Package deal.swift file.

For some fundamental terminology: we outline sure merchandise (i.e. static library, dynamic framework, app bundle and many others, useful resource bundle, unit take a look at bundle), that relate to quite a few targets (a bucket for a bunch of supply code information and assets). Here’s a distinction from Xcode the place goal and product is used synonymously.

Package deal Definition

Step one, and most vital one, is so as to add a package deal definition file to the basis folder of the repository. It must be on this place as a result of Swift Packages are referenced by the repository URL and SwiftPM will solely take a look at the highest folder for Package deal.swift.

Right here’s the definition for Kvitto, for reference. This has all components you would possibly encounter, together with a dependency on one other package deal, a few assets on prime of the definition of 1 product and a number of goal.

// swift-tools-version:5.3

import PackageDescription

let package deal = Package deal(
    title: "Kvitto",
    platforms: [
        .iOS(.v9),         //.v8 - .v13
        .macOS(.v10_10),    //.v10_10 - .v10_15
        .tvOS(.v9),        //.v9 - .v13
    ],
    merchandise: [
        .library(
            name: "Kvitto",
            targets: ["Kvitto"]),
    ],
    dependencies: [
        .package(url: "https://github.com/Cocoanetics/DTFoundation.git", 
		from: "1.7.15"),
    ],
    targets: [
        .target(
            name: "Kvitto",
            dependencies: [
                .product(name: "DTFoundation", 
				package: "DTFoundation"),
            ],
            path: "Core",
            exclude: ["Info.plist"]),
        .testTarget(
            title: "KvittoTests",
            dependencies: ["Kvitto"],
            path: "Check",
            exclude: ["Info.plist"],
            assets: [.copy("Resources/receipt"),
                        .copy("Resources/sandboxReceipt")]),
    ]
)

The primary line would possibly solely appear like a remark to you, however it’s important for the swift instruments to find out what syntax components are supported. Model 5.3 is required when you’ve got assets in any goal. In case you set that to one thing decrease you get syntax errors relating to the useful resource definitions. In case you set that to five.3 however don’t specify useful resource definitions (for non-standard assets) you’ll get warnings about unknown information that you need to both exclude or outline as assets.

I discovered myself conflicted about that, as I had talked about within the earlier article. All code would work on Swift 5.0 and up and solely the take a look at goal has assets. I might get extra inexperienced checkmarks on Swift Package deal Index if I eliminated the .testTarget definition.

On the opposite aspect the swift instruments allow you to run thusly outlined unit checks from the command line and functioning unit checks additionally ought to rely as an indication of excellent library high quality. Lastly, everyone ought to be utilizing Swift 5.3 anyway as that’s the baseline normal because the launch of Xcode 12.

That’s why I selected to depart it at that.

The fundamental setup of the package deal definition is simple. You could have the package deal title, then some minimal platform variations. Notice that these minimal OS variations don’t imply that that would limit the the package deal to particular platforms.

The merchandise part defines what sort of library comes out of the construct course of. The default setting (invisible) is to supply a static library, by specifying kind: .dynamic you get a dynamic framework as an alternative. The targets array specifies which targets will get merged into the ultimate product.

I assumed for a second that that could be good to have the assets be added to the framework as an alternative of a separate useful resource bundle, like we’re used to. However alas the dealing with of assets stays the identical they usually get bundled right into a Product_Target.bundle. So subsequently I’d somewhat have the static library – which is able to get merged into the app binary – somewhat than having one more separate framework bundle contained in the app bundle.

As I defined within the earlier article, dynamic frameworks ought to be prevented if the supply code for libraries is public. So we’re proud of the static library default.

The dependencies part lists the exterior reference to different packages. You specify the repository URL and the minimal variations. The proven manner with from and a model would settle for all 1.x.x variations from and together with 1.7.15. There are additionally different methods to specify a precise quantity or sure ranges.

Final come the targets. We now have a daily goal for the package deal and a take a look at goal for all of the unit checks. In case you don’t specify a path then SwiftPM expects the supply code within the Sources folder beneath the goal’s folder and assets in a Sources folder. I’ve a unique construction, so I specified a customized path.

I’ve to exclude the Information.plist for each targets as a result of that is utilized by two targets outlined contained in the Xcode undertaking. And for the take a look at goal I specify two assets to be copied with the trail relative to the goal customized path. These copy directions are crucial as a result of the contained assets don’t have a sort that Xcode is aware of easy methods to deal with. For issues like strings information or XIBs you don’t need to specify something.

Evaluate the dependencies key of each targets. On the one hand you see that I’m referencing the exterior dependency of the principle goal. Then again the take a look at goal requires the principle goal to work. That’s additionally a distinction to Xcode the place the examined code resides inside a bunch utility, the place’s right here it’s compiled into the unit take a look at bundle.

Goal Issues

You could be questioning why there’s a distinction between merchandise and targets in SPM. One purpose for that you’ve got already seen: there isn’t any purpose for the take a look at goal to be represented in a product. Easy packages will usually solely have one product that may solely consist of 1 goal.

Though I already discovered two extra causes, to separate code out into extra particular person targets after which additionally merchandise.

You would possibly assume that Swift Package deal Supervisor would solely all you to have code written in Swift. However you’ll be incorrect, Any language goes, additionally Goal-C and different C dialects. However SPM doesn’t permit you to combine C-based languages with Swift in a single goal.

In a single undertaking I had some Goal-C code for a operate with numerous ifs. I rewrote that in Swift solely to search out that compiling this could take greater than a minute, in contrast to a couple seconds in Goal-C. So I selected to depart the operate because it was. The answer was to place it right into a separate Goal-C goal and refer that to an inner dependency from the principle Swift goal.

The opposite good purpose for a separate goal and product was to have some frequent knowledge mannequin code that may be utilized by inner targets and likewise by way of import in an app consuming my library. In locations the place the consumer would solely want the shared definitions he would import the precise module for that. Elsewhere he would import different targets which in flip might additionally make use of these definitions internally.

Every product turns into its personal module.

Resourcefulness

I discussed above which you could let SPM do its personal factor in relation to normal useful resource sorts, like localised strings, XIBs, storyboards and asset catalogs. In case you use string localisation although, it’s important to specify the undertaking’s default language.

Different sorts it’s important to both particularly exclude or specify what ought to be completed for it. You possibly can both specify a .copy for every particular person useful resource or additionally for the whole Sources folder. Since I’ve solely two take a look at information and that’s not going to vary, it wasn’t an excessive amount of work so as to add these individually.

SPM expects assets in the identical folder {that a} goal’s supply information reside in (or a sub-folder thereof). The rationale for that’s once more that there isn’t any Xcode undertaking file the place you may specify membership of sure information to particular targets. You specify what belongs the place by how it’s specified by the file system together of the package deal definition.

Say you’ve got a single place the place you’ve got localised strings information downloaded from a translation web site like POEditor however you need them to be included in numerous targets. A method to attain that’s to create soft-links contained in the goal’s useful resource folders to the information. I wrote this shell script to create the lproj folders for all languages after which create the hyperlinks.

#!/bin/sh

echo "Eradicating current strings"
rm -rf ../TFMViews/Sources/*.lproj
rm -rf ../TFMExtension/Sources/*.lproj

PWD=`pwd`

for entry in *.lproj
do
  echo "Linking $entry..."

  mkdir ../TFMViews/Sources/$entry
  ln -s ../../../Strings/$entry/TFMViews.stringsdict 
     ../TFMViews/Sources/$entry
  ln -s ../../../Strings/$entry/TFMViews.strings 
     ../TFMViews/Sources/$entry

  mkdir ../TFMExtension/Sources/$entry
  ln -s ../../../Strings/$entry/TFMExtension.stringsdict 
     ../TFMExtension/Sources/$entry
  ln -s ../../../Strings/$entry/TFMExtension.strings 
     ../TFMExtension/Sources/$entry

completed

The identical strategy of soft-links will also be employed for Goal-C primarily based packages the place you may hyperlink to all related public headers in an embody folder.

Platform-specific Code

Because the package deal has no facility for limiting particular supply code to particular platforms or OS variations, you’ll face the state of affairs that sure code received’t compile for different platforms. A workaround for this limitation is using conditional compilation directives.

For instance, the whole lot that references UIKit can’t be compiled for macOS or watchOS, so I’ve a couple of locations in DTCoreText or DTFoundation (each written in Goal-C) the place the whole implementation is enclosed in:

#import <TargetConditionals.h>

#if TARGET_OS_IPHONE && !TARGET_OS_WATCH
...
#endif

I additionally discovered that typically I needed to additionally import the TargetConditionals header for the defines to work. Specifically sure Goal-C class extensions in DTCoreText wouldn’t be seen within the public interface if I didn’t import this header. I’ve no clarification as to why, however including the import for the header mounted it.

Contained in the Xcode Venture

The adjustments for conditional compilation apart, there may be nothing you have to change in your Xcode undertaking – except you wish to. The principal setup for the package deal occurs in Package deal.swift. You possibly can construct the package deal with issuing swift construct.

I discovered it handy so as to add a reference to the package deal contained in the Xcode undertaking as a result of this lets you debug your code within the context of being compiled for a package deal. In case you drag any folder (containing a package deal definition) into the undertaking navigator pane, Xcode will add an area package deal reference for you, with a logo of a cute little field.

In Xcode 12 there’s a bug that if you happen to try this for the undertaking folder itself, it appears to work, however when you shut the undertaking and reopen it once more, the reference turns into defunct. The best way to repair it’s to vary the reference to “Relative to Venture” and open the folder selector by way of the folder button and re-select the undertaking root folder.

This additionally creates a scheme for constructing the package deal and the package deal’s merchandise turn out to be obtainable to hyperlink/embed to your app. Package deal merchandise have an icon of a greek temple. If they’re static libraries then they’ll get merged into the app binary, dynamic frameworks might be added to the app’s Frameworks folder.

Xcode additionally creates a scheme for the package deal, putting it in .swiftpm/xcode/xcshareddata/xcschemes/. I moved it into the shared schemes folder of the xcodeproj and renamed it to Kvitto-Package deal.xcscheme.

I had the watchOS platform builds on Swift Package deal Index fail as a result of xcodebuild insists on constructing all targets, together with the take a look at goal. This fails as a result of unit checks require XCTest which doesn’t excite for watchOS.

By offering an aptly named shared scheme it would solely construct the principle goal and I achieved inexperienced checkmarks for watchOS on SPI.

Library Unit Assessments

To run the unit checks contained within the take a look at goal, all you have to do is to run swift take a look at on the command line, from the repository root folder.

Some magic was required to get that to work as a result of take a look at information required by the unit checks are usually not bundled within the .xctest bundle. For normal packages a useful resource bundle accessor is being robotically generated, which you should utilize with Bundle.module.

The accessor works by figuring out the trail of the executable and setting up a bundle title from names of package deal and goal. Within the case of unit checks the executable is xcrun contained within the Xcode.app bundle the place it has no likelihood of discovering the Kvitto_KittoTests.bundle.

My ugly, however practical, workaround for that is as follows:

func urlForTestResource(title: String, ofType ext: String?) -> URL?
{
	let bundle = Bundle(for: kind(of: self))
		
	#if SWIFT_PACKAGE
		
	// there's a bug the place Bundle.module factors to the trail of xcrun contained in the Xcode.app bundle, as an alternative of the take a look at bundle
	// that aborts unit checks with message:
	//   Deadly error: couldn't load useful resource bundle: /Purposes/Xcode.app/Contents/Developer/usr/bin/Kvitto_KvittoTests.bundle: file KvittoTests/resource_bundle_accessor.swift, line 7
		
	// workaround: attempt to discover the useful resource bundle on the construct path
	let buildPathURL = bundle.bundleURL.deletingLastPathComponent()
		
	guard let resourceBundle = Bundle(url: buildPathURL.appendingPathComponent("Kvitto_KvittoTests.bundle")),
	   let path = resourceBundle.path(forResource: title, ofType: ext) else
	{
		return nil
	}
		
	return URL(fileURLWithPath: path)
		
	#else
		
	guard let path = bundle.path(forResource: title, ofType: ext) else
	{
		return nil
	}
		
	return URL(fileURLWithPath: path)
		
	#endif
}

This depends on the truth that the useful resource bundle might be created parallel to the xctest bundle, in the identical construct folder. The #if SWIFT_PACKAGE conditional compilation will solely be added if this code is constructed as a part of a swift package deal. With this workaround, the earlier mechanisms of operating the unit take a look at scheme by way of Xcode continues to work.

The wonderful thing about Swift being open supply, is that we are able to additionally examine the code for the useful resource accessor on GitHub. It seems that the talked about bug has already been addressed there. The repair was made too late to make it into Swift 5.3 in Xcode 12 however has been confirmed to be current in Xcode 12.2.

Conclusion

I discover that the evolution of Swift Package deal Supervisor as progressed sufficiently to begin including help for it to my libraries. It’s doable and advisable to take action along with different methods of integration, like Xcode subproject, Cocoapods or Carthage.

Essentially the most annoying limitation remaining is that you just can not restrict targets to sure platforms or specify a spread of supported OS variations per goal. However these can simply be labored round with conditional compilation directives.

The standard standards partially enforced by the Swift Package deal Index coupled with the discoverability of parts additionally make it engaging for library distributors to contemplate supporting Swift Package deal Supervisor. Having the dependency administration taken care of by Xcode is the best characteristic of all.

Additionally revealed on Medium.

Classes: Administrative