> On Nov 22, 2016, at 3:28 AM, rintaro ishizaki via swift-users
> <swift-users@swift.org> wrote:
>
> Hi Said,
>
> Since `Package.targets` is a mutable public property,
> https://github.com/apple/swift-package-manager/blob/master/Sources/PackageDescription/Package.swift#L60-L67
>
> <https://github.com/apple/swift-package-manager/blob/master/Sources/PackageDescription/Package.swift#L60-L67>
> you can freely mutate it later, as documented in
> https://github.com/apple/swift-package-manager/blob/master/Documentation/Reference.md#customizing-builds
>
> <https://github.com/apple/swift-package-manager/blob/master/Documentation/Reference.md#customizing-builds>
Right. If they were immutable, it seems that another (more general) solution
to this would be to relax the restrictions around #if checks, enabling them to
apply to elements in lists. That would allow you to write:
let macOnlyTargets = [
#if !os(Linux)
.Target(name: "SomeMacOSTarget")
#end
]
-Chris
>
>
> 2016-11-22 4:21 GMT+09:00 Said Sikira via swift-evolution
> <swift-evolut...@swift.org <mailto:swift-evolut...@swift.org>>:
> Hello everyone,
>
> Currently, we use Package.swift manifest file when defining our packages.
> Within the manifest file you define your targets, dependencies, excluded
> folders etc. This works fairly well while you’re using frameworks that exist
> on all supported platforms (ex. Foundation).
>
> The main problem starts if you want to use code that exists only on macOS
> platform, for example, if you want to use Objective C runtime calls or UIKit.
> Then, you need to use bunch of #if os(Linux) to define what’s available on
> Linux and what’s available on macOS. While this approach can be non
> problematic for simple projects, it can introduce unnecessary complexity if
> you have a large target and dependency graph.
>
> One way people tackle this problem is writing something like this:
>
> #if os(Linux)
> let macOnlyTargets = []
> #else
> let macOnlyTargets = [
> .Target(name: "SomeMacOSTarget")
> ]
> #end
> This structure looks even worse if you need to define more complex behaviors.
> For example, look at the RxSwift Package.swift
> <https://github.com/ReactiveX/RxSwift/blob/master/Package.swift> file. In my
> case, I try to write #if os(Linux) as little as possible which leads me to
> writing my packages like:
>
> #if os(Linux)
> // Define full Linux package
> let package = Package(...)
> #else
> // Define full macOS package
> let package = Package(..)
> #end
> Proposal
>
> I propose that we support using different file for writing Linux package
> manifests. This file could be named:
>
> PackageLinux.swift
> Package.Linux.swift
> Package.linux.swift
> Inside this file you would be able to define your package only for Linux in
> the same way you’re defining one in regular Package.swift. The defined
> behaviors of building a package would be:
>
> If building on Linux and PackageLinux.swift is present, use that file when
> building the package.
> If building on Linux and PackageLinux.swift is not present, use regular
> Package.swift manifest.
> If building on macOS always use Package.swift manifest.
> Possible problems
>
> This behavior would only introduce problems when SPM gains support for new
> platforms, but then again, you would need to use new #if os(somethingNew)
> checks.
>
> Compatibility with current packages
>
> This would be only a additive feature for Swift Package Manager and backwards
> compatibility will be maintained.
>
>
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