API-s don't return "requires_dist" for most packages

[aivarannamaa]

I'm writing a simple pip GUI, which is supposed to show information about packages available at PyPI. Among this information I would like to list the required packages.

While browsing API result of one of my own packages (https://pypi.python.org/pypi/thonny/2.0.7/json) I got the impression that requirements are given under key "dist_requires".

To my surprise, most packages I tried (and which do have dependencies), don't have this key in their API result. Examples:

• https://pypi.python.org/pypi/matplotlib/2.0.0/json
• https://pypi.python.org/pypi/pandas/0.19.2/json
• https://pypi.python.org/pypi/Sphinx/1.5.3/json

Same thing with XML-RPC

I inspected setup.py of Sphinx (https://github.com/sphinx-doc/sphinx/blob/master/setup.py) and it uses setuptools and install_requires, just like Thonny (https://bitbucket.org/plas/thonny/src/b9e4c19f02367341827777780834e9eefbdd2265/setup.py?at=master&fileviewer=file-view-default).

I can't see why is requires_dist missing from Sphinx's API output.

[aivarannamaa]

I now noticed that XML-RPC with ServerProxy('https://pypi.org/pypi') does give dist_requires for Sphinx but it's empty list.

[jamadden]

I suspect you'll find that the difference is whether the project uploads binary wheels (and whether they upload the binary wheel first if they upload wheels and sdists). PyPI appears to only extract this extra metadata from a wheel, and only if a wheel is the first artifact uploaded for a release (I haven't checked the code for that, but that's my experience). This is part of the reason why tools like twine upload wheels first.

[di]

Regarding the missing field, I'd recommend pointing your pip GUI at pypi.org instead, where the requires_dist field will always be present even if empty (see our migration guide here).

Regarding why the requires_dist field is sometimes empty, I'm closing as this is expected behavior. For more background on why, see https://di.codes/articles/2018/03/05/why-pypi-doesnt-know-dependencies