[Email-SIG] fixing the current email module

[Barry Warsaw]

On Oct 8, 2009, at 6:46 AM, Stephen J. Turnbull wrote:

> Barry Warsaw writes:
>
>> I've also heard convincing arguments from folks in the Python
>> community in both camps: "using anything other than strings
>> internally is insane; no, using anything other than bytes
>> internally is insane."
>
> They're both right, of course.  The problem is figuring out who is
> right when. ;-)

Indeed!

>> Just to ramble a little longer, it's been argued that we should give
>> up on idempotency, but I'm not convinced.
>
> If we can't achieve ... ah, isn't "invertibility" what you mean here?
> ... "idempotency", then we're dropping information somewhere along the
> line.  Also, there are part types (pgp-signed, I'm looking at you)
> where it's absolutely essential that we be able to roundtrip the body
> byte for byte.  So I'm -1 on giving up.

Yeah, "idempotency" probably is not the right term, though I think  
historically that's what's been used.  Math geeks, what's the right  
term here? :)

I completely agree with you (of course :).  The way I look at it is  
that we lose this important principle only when the source data lacks  
complete information, i.e. is defective.  Although we can still invert  
in the face of some defects (and we should), I think we officially  
make no such guarantees unless the model is defect-free.

-Barry

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