[Distutils] What metadata does pip actually need about sdists?

[Marcus Smith]

> since we're simply talking about name/version constraints (not
platform/python)

let me clarify that... since I imagine someone might bring up markers in
response...
markers allow you to vary your name/version dependencies by environment
(for example, by platform and python version),
but to be clear, it's still not a "binary" dependency declaration... i.e.
the dependency is still declared by name and a version specifier alone.


On Sun, Oct 11, 2015 at 10:48 AM, Marcus Smith <qwcode at gmail.com> wrote:

>
>
>> 2) after unpacking this sdist it then calls 'setup.py egg_info' to get
>> the full metadata for the wheel
>
>
> I wouldn't say "get the full metadata for the wheel".  it's not a wheel
> yet.
> `egg_info` run so we can use the pkg_resources api to find the
> dependencies.
>
>
>
>> Specifically what it does with this is
>> extract the setup_requires and install_requires fields
>
>
> specifically, we call `requires` on pkg_resources distribution objects
> https://github.com/pypa/pip/blob/develop/pip/req/req_set.py#L583
>
>
>
>> 3) eventually it actually builds the package, and this produces a
>> wheel (or wheel equivalent) that has its own metadata (which often
>> matches the metadata from egg_info in step (2), but not always)
>>
>
> "not always"?  not following your point
> they're 2 different formats, but should contain the same essential
> information.
> here's the wheel code that does the conversion
>
> https://bitbucket.org/pypa/wheel/src/1cb7374c9ea4d5c82992f1d9b24cf7168ca87707/wheel/metadata.py?at=default&fileviewer=file-view-default#metadata.py-90
>
>
>
>> name and version before it runs egg_info, I assume that what this
>> means is that it's crucial for pip to have static access to dependency
>> information?
>
>
> yes
>
>
>
>> It would be somewhat convenient if sdists did list their binary
>> dependencies:
>
>
> not sure about your insertion of "binary" here.
> pip is concerned with finding python project dependencies (i.e. name and
> version constraints) in the sdist
> and then based on the current install environment, it will further
> constrain the wheels chosen based on architecture and python implementation.
> and to be perfectly clear, none of this deals with non-python OS/Distro
> requirements.
>
>
>
>> 3) if any of the packages-to-be-installed are sdists, then fetch them,
>> run egg_info or build them or whatever to get their real dependencies,
>> add these to the graph, and go to step 1
>>
>
> this is the pain we don't want in the future.
>
> since we're simply talking about name/version constraints (not
> platform/python), It's hard to conceive that we'd agree on an sdist spec
> that didn't include that.
>
>
>
>> Do the relevant pip maintainers
>> even read this mailing list? :-)
>>
>
> I try  :  )
>
>
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