# PEP 685: Comparison of extra names for optional distribution dependencies

**URL:** <https://discuss.python.org/t/pep-685-comparison-of-extra-names-for-optional-distribution-dependencies/14141>\
**Category:** Packaging\
**Created:** [March 9, 2022, 1:37am UTC](https://discuss.python.org/t/pep-685-comparison-of-extra-names-for-optional-distribution-dependencies/14141 "2022-03-09T01:37:31Z")\
**Posts on this page:** 1\
**Showing post:** 33

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**Author:** ![CAM-Gerlach](https://sea2.discourse-cdn.com/flex002/user_avatar/discuss.python.org/cam-gerlach/32/3688_2.png) [@CAM-Gerlach](https://discuss.python.org/u/CAM-Gerlach)\
**Post date:** [March 14, 2022, 8:23pm UTC](https://discuss.python.org/t/pep-685-comparison-of-extra-names-for-optional-distribution-dependencies/14141/33 "2022-03-14T20:23:27Z")

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> [@pf\_moore](#):
>
> The only context in which “an older core metadata version” can be specified is in the case of a metadata _consumer_ reading data generated by a tool that hasn’t been updated for the new spec. In that case, the consumer should warn, so that the user knows that the extra will have to change in future.

Ah okay, thanks, that does make more sense in the context of a metadata consumer—I had been thinking just in terms of a producer.

> [@pf\_moore](#):
>
> You seem to be thinking in terms of multiple valid metadata formats (one for each version). That’s not a helpful way of thinking of things - there’s only _one_ metadata format, and it gets updated over time.

Actually, the latter was more or less what I intended to meant by

> [@CAM-Gerlach](#):
>
> since the core metadata spec is only specifying the current version, I’m not sure it makes sense to discuss older versions

but I was only thinking in terms of the context of a metadata producer rather than a consumer.

> [@pf\_moore](#):
>
> Yes, the spec says […] IMO that’s a mistake

Why, you don’t say… 😛

> [@Non-sequential acceptance and implementation of new Core Metadata features and changes](https://discuss.python.org/t/non-sequential-acceptance-and-implementation-of-new-core-metadata-features-and-changes/14233/4):
>
> One other related point: the [`Metadata-Version`](https://packaging.python.org/en/latest/specifications/core-metadata/#metadata-version) section of the core metadata spec states
> 
> > For broader compatibility, build tools MAY choose to produce distribution metadata using the lowest metadata version that includes all of the needed fields.
> 
> […] Is that something we really want to explicitly endorse?

I’ve opened a pull request as [pypa/packaging.python.org#1063](https://github.com/pypa/packaging.python.org/pull/1063); should I open (yet) another dedicated thread to ensure this has appropriate visibility, or should we just wait for further discussion on [the existing thread](https://discuss.python.org/t/non-sequential-acceptance-and-implementation-of-new-core-metadata-features-and-changes/14233)?

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