[Distutils] wheels on sys.path clarification (reboot)

[Noah Kantrowitz]

On Jan 29, 2014, at 2:59 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:

> But that's what I'm saying, there are only three ways to break this behaviour:
> 
> 1. Changing the wheel format in such a way that we drop support for being able to install simple wheel files without a specialised installer
> 2. Break zipimport itself to explicitly disallow wheel files
> 3. Switch to a zipimport incompatible compression scheme
> 
> The first two aren't going to happen, which leaves only the third.
> 
> You appear to be saying that you would like to reserve the right to switch to a zipimport incompatible compression format in future versions of the wheel spec. If you're *not* saying that, then what independent design decision is there to be discussed that makes the new FAQ anything other than a clarification of the status quo? The rest of the behaviour is inherent in the "no specialised installer needed" feature.
> 
> People saying "I didn't realise that the current design implied zipimport compatibility" is *why* I added the clarification, so it's not a compelling argument in convincing me that the clarification wasn't needed or is inappropriate.

If you are going to document this, and it is not going to be explicitly supported by the spec (it isn't), the _only_ logical thing is to document that this is undefined behavior and while it works now, people should not depend on it. Under no circumstance should we document this as "well it works right now" without guidance about the fact that it isn't part of the spec and is _not_ a candidate for future design decisions. If someone would like to propose amending the spec that can happen separately, but as it stands right now this is nothing but convenient, undefined behavior.

--Noah

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