> On Nov 12, 2016, at 9:43 PM, Russ Bishop <xen...@gmail.com> wrote:
> 
> 
>> On Nov 12, 2016, at 1:02 PM, Daniel Dunbar via swift-build-dev 
>> <swift-build-...@swift.org> wrote:
>> 
>> Hi all,
>> 
>> I'm reposting a request for feedback on my proposal for extending SwiftPM to 
>> support multiple packages inside one repository (i.e. "monorepo" support, 
>> although it is a misnomer in this use case).
>> https://github.com/ddunbar/swift-evolution/blob/multi-package-repos/proposals/NNNN-swiftpm-multi-package-repos.md
>> 
>> I would like to move this proposal forward so we can start on an 
>> implementation, even if we need to refine it over time, but I was hoping to 
>> get at least some concrete feedback first.
>> 
>> Thanks,
>> - Daniel
> 
> 
> It seems like you’re going through contortions to deal with arbitrary 
> directory layouts and some odd consequences fall out of that decision. Not 
> being able to deterministically detect non-unique sub-packages is one. 
> 
> Why not just require a top-level Package.swift that explicitly specifies the 
> sub-packages? The name for the sub-package should be in the main package 
> manifest. You’d gain the ability to import all the sub-packages in one go; 
> importing the root package without any sub-packages specified automatically 
> imports all sub-packages. This also allows library authors to organize a 
> library into sub-packages later without breakage. Come up with a convention, 
> e.g. a sub-package is in “/subpackageName” but allow overriding that default. 
> That allows reorganization if needed but the convention should work for most 
> libraries.

Mostly because I am concerned this doesn't scale well to *very* large 
repositories, in which commits to that file would be "contentious" (in the lock 
contention sense, not subject to debate sense). Of course, this argument is a 
little bogus as the current proposal doesn't scale that great either since we 
have to discover the packages (although I believe we can probably do a good job 
of caching this information).

It certainly would simplify the implementation & proposal to have this.

The other reason is it is yet another thing for people to maintain (and 
remember the syntax for). Most repos are small enough that I think the current 
proposal would perform fine and have a tendency to do what people might naively 
expect (even if they didn't really think about why). On the other hand, this 
file is likely to be quite static, so I'm not sure that is a very important 
issue.

I was already on the fence on this, but I hadn't considered the benefits you 
mention of allowing import of the package w/ no sub package specifier to mean 
import of all sub-packages. That tips me a little more towards thinking maybe a 
better proposal is to KISS and require this in some root file (whether or not 
that root file is itself a package manifest or a different kind of file is 
another question, you assume it would be the regular package manifest but I 
don't think it *need* be, and there is some value in not having any nesting 
relationship amongst packages).

 - Daniel

> A top-level Package.swift would also allow immediate detection of non-unique 
> sub-packages, etc. Also if you are using things like git submodules, subtree, 
> or some other mechanism that ends up putting package files in your source 
> tree you don’t automatically re-export that package unless you take explicit 
> action.
> 
> 
> I like the idea in general.
> 
> 
> Russ

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