Add support for reading dependencies

[jaraco]

In GitLab by @jaraco on Sep 26, 2018, 24:57

I recently stumbled onto another case where pkg_resources supplies some important metadata, the dependencies for a package.

~ $ pkg_resources.get_distribution('jaraco.functools').requires()
[Requirement.parse('more-itertools')]

I believe importlib_metadata should probably provide at least a list of requirements if not also possibly parsing those requirements (although the latter might only work if the third-party 'packaging' library is available).

[jaraco]

In GitLab by @warsaw on Sep 28, 2018, 22:14

Is this just a matter of parsing the Requires-Dist headers from the METADATA file? Would the API have to mirror pkg_resources?

+1 for providing that as a convenience.

[jaraco]

In GitLab by @jaraco on Nov 11, 2018, 02:03

Is this just a matter of parsing the Requires-Dist headers from the METADATA file?

Yes, probably.

Would the API have to mirror pkg_resources?

Not necessarily.

[jaraco]

In GitLab by @jaraco on Nov 11, 2018, 02:03

assigned to @jaraco

[jaraco]

In GitLab by @jaraco on Nov 11, 2018, 02:11

Is this just a matter of parsing the Requires-Dist headers from the METADATA file?

In order to support editable installs, it would also need to parse out the egg-info/requires.txt.

It should also probably present which 'extras' are provided and what their dependencies are...

And it should either wrap the results in objects from packaging or provide instructions on how to use the outputs from to pass to packaging for enhanced functionality.

[jaraco]

In GitLab by @jaraco on Nov 11, 2018, 02:31

Gah. The egg-info format for requires.txt looks like this:

dep1
dep2

[extra]
extra1dep1

[extra2]
extra2dep1

That file, although it looks like an .ini file doesn't have a heading for the first section, so fails when loaded with a ConfigParser.

Looking at pkg_resources, it uses this function to hand-parse the file. I'm wondering if it's safe to just inject a special section and then use the configparser.

[jaraco]

In GitLab by @jaraco on Nov 11, 2018, 02:35

Nope. ConfigParser also doesn't read simple lines from sections.

[jaraco]

In GitLab by @jaraco on Nov 11, 2018, 02:59

mentioned in commit 0ab7f13cd79e6b26839b77471fe1d5cf89773c37

[jaraco]

In GitLab by @jaraco on Nov 11, 2018, 03:01

This work is once again making me want to revisit the idea of splitting PathDistribution into separate classes for dist-info and egg-info. It's also making me wonder if we shouldn't instead concentrate our efforts on eliminating egg-info and getting proper editable installs into pip that generate dist-info. I know there are some efforts under consideration to make that happen.

[jaraco]

In GitLab by @jaraco on Dec 1, 2018, 02:56

mentioned in commit 43185e0

[jaraco]

In GitLab by @warsaw on Dec 3, 2018, 19:31

@jaraco Yes, ideally we'd be able to eliminate egg-infos, but gosh that does seem like long-tail territory. Given that at least for now we have to support editable installs, it seems like that forces our hand for egg-info support.

If you split PathDistribution will you also have to split WheelDistribution too?

[jaraco]

In GitLab by @jaraco on Dec 7, 2018, 22:18

If you split PathDistribution will you also have to split WheelDistribution too?

No, because wheels will never be eggs. But if we decide to support eggs, that will have a comparable split.

[jaraco]

In GitLab by @jaraco on Dec 16, 2018, 19:45

mentioned in merge request !31