Ah sorry! I was under the impression the “optimistic candidate” was being 
proposed as one derived from a specifier supplied in the direct dependency line 
by the user. If it’s a first guess essentially, I think that’s how we operate 
anyway for the most part (at least in the future resolver) while we step 
through the dependency graph. 

My main question is whether you’d consider a dependency specified in pep508 
form as satisfying other things that demand the given name even if, upon 
download, the version doesn’t indicate that.  If not, it still feels like we 
need to download it first. Just because someone put a ref doesn’t mean they 
don’t update that ref’s content :/


Dan Ryan // pipenv maintainer
gh: @techalchemy

> On Jan 29, 2019, at 7:15 PM, Nathaniel Smith <n...@pobox.com> wrote:
> 
>> On Tue, Jan 29, 2019 at 4:11 PM Dan Ryan <d...@danryan.co> wrote:
>> 
>> In the ideal future would we avoid the build step by having PyPI host 
>> primarily wheels? In which case anything available on PyPI would hopefully 
>> have its metadata exposed on the JSON endpoint and we could sidestep that.
>> 
>> Either way we will ultimately have to download whatever is specified as a 
>> direct url dependency because even if it has a version that aligns we will 
>> need to figure out what dependencies it demands, etc etc. And while an 
>> optimistic candidate is a neat idea it’s not clear to me at least whether 
>> it’s a good idea to expect this of users. What happens when they get it 
>> wrong? Do you trust the version in the package or do you allow an override?  
>> Conflict resolution is possible either way but the desired behavior there 
>> would seem to favor the former imo
> 
> Everything I was talking about was stuff that would be happening
> inside the resolver loop, no users involved. The "optimistic
> candidate" would just be an initial tentative solution that the
> resolver uses internally to decide which things to try downloading
> first.
> 
> You know more about how resolvers actually work than I do though, so I
> might have gotten it wrong :-).
> 
> -n
> 
> -- 
> Nathaniel J. Smith -- https://vorpus.org
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