[swift-build-dev] Test-only dependencies

[Daniel Dunbar]

> On Aug 29, 2016, at 2:35 AM, Honza Dvorsky <jan.dvorsky at me.com> wrote:
> 
> Not sure if already mentioned, but the issue of duplicated dependencies in targets can be easily handled like this:
> 
> import PackageDescription
> 
> let sharedDependency: Package.Dependency = .Package(url: "...", majorVersion: 1)
> 
> let package = Package(
>     name: "MyPkg",
>     targets: [
>         .Target(name: "First"),
>         .Target(name: "Second", dependencies: ["First", sharedDependency]),
>         .Target(name: "Third", dependencies: [sharedDependency])
>     ]
> )
> 
> That's assuming we'll be able to add external deps to targets.

I'm not sure that is a syntax we want to support per the long term plans to split the manifest into a "leading package specification" which, while Swift, is a restricted subset we know we can parse into a machine editable form.

I would like it if the syntax for all common things was representable as a readable declarative initializer.

 - Daniel

> 
> - Honza
> 
> On Mon, Aug 29, 2016 at 7:07 AM Daniel Dunbar via swift-build-dev <swift-build-dev at swift.org <mailto:swift-build-dev at swift.org>> wrote:
> I completely agree with your original email, and agree the target-access control proposal amounts to a variant of #2.
> 
> We definitely need a per-target dependency solution, and if we got one that included some kind of solution for managing the duplicate declaration, that would solve the con you list with #2. That might suggest that one approach here is to add it the list of reasons we should do a per-target dependency proposal.
> 
> On the other hand, that has proven more complicated than approach #1, and is likely to take longer to get right. I wonder if there are reasons we might end up wanting #1 even if we had a working #2 (one reason might be if we couldn't solve the duplicate declaration problem).
> 
> My leaning here is towards trying to figure out a good approach for #2 first, and see where that leaves us, but I could probably be persuaded that the problem is pressing enough we should consider a more targeted fix sooner.
> 
>  - Daniel
> 
> > On Aug 28, 2016, at 7:48 PM, Paul Cantrell via swift-build-dev <swift-build-dev at swift.org <mailto:swift-build-dev at swift.org>> wrote:
> >
> >
> >> On Aug 28, 2016, at 9:23 PM, Ankit Aggarwal <ankit_aggarwal at apple.com <mailto:ankit_aggarwal at apple.com>> wrote:
> >>
> >> I agree that building test specific dependencies is not useful for packages which just uses the some package, however I think that should be controlled by some other general mechanism like specifying exact external package/target the target in question depends on.
> >
> > That’s what I had in mind with “Approach 2” in my original message. Approach 3 is a related but different alternative.
> >
> > Please see remarks in the original message for my take on the pros and cons.
> >
> >> That way all the unused targets in an external package will not build. See thread “Proposal: SwiftPM Target Access Control“ for some more discussion on this idea.
> >
> > That proposal is getting warm — especially if test packages are _not_ exposed by default, something it seems to me that proposal should specify.
> >
> > The new “External” in that proposal has the right semantics, but seems to me to add yet more complexity to a package DSL whose readability is already a bit strained. In particular, this seems likely to cause confusion:
> >
> >> An external package dependency declaration implicitly becomes dependency of each target in the package. We propose this behaviour should be retained but if a target dependency contains an External declaration then all other targets which wants to use that external dependency should explicitly state their dependency on that external package using External.
> >
> > Cheers,
> >
> > Paul
> >
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