> On Jan 30, 2017, at 11:43 PM, Martin Waitz <t...@admingilde.org> wrote:
>
> Hi Boris,
>
>> Am 31.01.2017 um 03:48 schrieb Rick Ballard <rball...@apple.com
>> <mailto:rball...@apple.com>>:
>>
>>>
>>> On Jan 25, 2017, at 11:06 PM, Martin Waitz via swift-evolution
>>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
>>>
>>> OK, you are right, branches can be helpful to have in the manifest.
>>> But I’m still confident that we must not put explicit version information
>>> into it.
>>> They belongs into the `Package.pins` file.
>>> That is enough to get reproducible builds.
>>
>> By "explicit version information", do you mean that you shouldn't put a git
>> revision hash in the manifest – only branches and version tags should be
>> acceptable?
>
> yes exactly.
> BTW: the more I think about it, the more I like the possibility to specify a
> branch in the manifest.
>
>> I'd agree that the revision-based initializer is a marginal feature;
>> normally your package should depend on a version range or is tracking a
>> branch. That said, we can imagine that you might wind up needing to peg your
>> dependency to a specific revision that isn't a version tag, and not track a
>> moving branch, so this seemed like a fairly harmless feature to add for that
>> case. What is your objection about supporting that?
>>
>> The decision about whether to put this information in your pins or in your
>> manifest should be driven by whether it's something your package requires,
>> or is just a workflow choice. If you just want to temporarily stick to a
>> specific revision of your dependency for workflow reasons, pinning is the
>> right way to do that. If, however, your package currently requires that
>> revision, and isn't going to work properly without it, then the manifest is
>> the right way to express that. You'd want that specification to stick even
>> if someone did `swift package update --repin` to get newer pinned revisions.
>
> Well, I guess your package will also work with all commits following your
> special one.
> Then I’d be enough to specify the branch: your special dependency version is
> already specified in the pins file and `swift package update` will only
> update to newer revisions.
>
> So why would you (temporarily) want to stick to a specific version?
> Because it happens to be the only compatible one at that time.
> So even that is a workflow thing and not a „this is the one and only“.
> And if you really really need to choose a specific commit which is in the
> past, then you can always create a special branch just for it.
>
> I really like to have a clear separation between manifest and the pins file.
> Otherwise I fear that inexperienced maintainers hard-code their dependencies
> to a specific version by accident.
> I've seen too strict version specifications too often already (e.g. on npm)
> ;-)
This is not for the case where a package will work with all commits on a branch
after the designated one. If that's the case, indeed a branch should be
specified instead. This is for the case where there is a specific commit that's
needed, and it doesn't have a version tag, and it either isn't on a current
branch or the branch has moved past it to something incompatible.
You can't necessarily create a special branch for such a commit because you may
not have permissions to push new branches to the repositories of your
dependencies.
One thing to note is that if a maintainer does use this feature
inappropriately, their package will fail once they tag it for release. One of
the behaviors specified by this proposal is that if a package is found via a
version tag, then if that package specifies any further dependencies via branch
or revision, that is an error. The rule is that any versioned tag needs to
fully specify all other dependencies via versioned tags. So a novice user will
find out pretty quickly that they can't rely on revision specifiers for their
actual releases.
In the future we hope to add a command to SwiftPM to help you prepare your
package for a tagged release. That process would check this for you, among
other things, so you'd find out about this problem before you created the tag.
- Rick
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