[Python-Dev] Edits to Metadata 1.2 to add extras (optional dependencies)

["Martin v. Löwis"]

Am 28.08.12 14:28, schrieb Daniel Holth:
> On Tue, Aug 28, 2012 at 8:07 AM, Donald Stufft<donald.stufft at gmail.com>  wrote:
>> I personally think that at a minimum we should have X-Fields that
>> get moved into the normal METADATA file, and personally I would
>> prefer to just drop the X- prefix completely.
>
> That is my preference as well. The standard library basically ignores
> every metadata field or metadata file inside or outside of metadata
> currently, so where is the harm changing the official document to read
> "you may add new metadata fields to metadata" with an updated standard
> library that only ignores some of the metadata in metadata instead of
> all of it. The community is small enough to handle it.

The problem with that (and the reason to introduce the X- prefix in RFC 
822) is that allowing arbitrary additions will make evolution difficult:
if you want to standardize a certain field at some point, you either 
need to pick a name that is unused in all implementations (which you 
never can be really certain about), or you break some existing tool by
making the addition (unless the addition happens to have the exact
same syntax and semantics as the prior use).

Regards,
Martin