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Re: Pre-RFC: Rename SVf_UTF8 et al.

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From:
Dan Book
Date:
August 18, 2021 20:08
Subject:
Re: Pre-RFC: Rename SVf_UTF8 et al.
Message ID:
CABMkAVUd+QfgLsgmTKvmHj4xnpc49Govif7wO05oX6Fg_z6etg@mail.gmail.com
On Wed, Aug 18, 2021 at 3:50 PM Tomasz Konojacki <me@xenu.pl> wrote:

> On Wed, 18 Aug 2021 13:18:34 -0400
> Felipe Gasper <felipe@felipegasper.com> wrote:
>
> > Per recent IRC discussion …
> >
> > PROBLEM: The naming of Perl’s “UTF-8 flag” is a continual source of
> confusion regarding the flag’s significance. Some think it indicates
> whether a given PV stores text versus binary. Some think it means that the
> PV is valid UTF-8. Still others likely hold other inaccurate views.
> >
> > The problem here is the naming. For example, consider `perl -e'my $foo =
> "é"'`. In this code $foo is a “UTF-8 string” by virtue of the fact that its
> code points (assuming use of a UTF-8 terminal) correspond to the bytes that
> encode “é” in UTF-8. The “UTF-8 flag”, however, is likely *not* set on this
> string. By contrast, consider `perl -Mutf8 -e'my $foo = "é"'`. Here $foo
> has the “UTF-8 flag” set, but $foo is NOT a “UTF-8 string” because its code
> points (in this case, only 1) aren’t valid UTF-8.
> >
> > The fact that quite often a “UTF-8 string” lacks the “UTF-8 flag”, and a
> “UTF-8-flagged” string is (usually) *not* a “UTF-8 string”, makes little
> sense except to the “highly initiated”.
> >
> > Another problem is “UTF-8” doesn’t really describe the “upgraded”
> format. This format is what Perl historically called “lax UTF-8” and is now
> widely called “generalized UTF-8”, which includes unpaired surrogates and
> code points above Unicode’s maximum.
> >
> > PROPOSAL: Rename the following identifiers in code and documentation,
> leaving macros for the old ones as aliases:
> > - SVf_UTF8        -> SVf_PVUPGRADED
> > - SvUTF8          -> Sv_PVUPGRADED
> > - SvUTF8_on       -> Sv_PVUPGRADED_on
> > - SvUTF8_off      -> Sv_PVUPGRADED_off
> > - SvPOK_only_UTF8 -> SvPOK_only_UPGRADED
> >
> > Note that flags like REFCOUNTED_HE_KEY_UTF8 do not need a rename because
> these indicate an actual (if incomplete/invalidated) UTF-8 decoding step.
> >
> > BENEFITS: Over time, this rename will minimize the confusion between
> Perl’s upgraded-PV storage format versus UTF-8. The rename may also compel
> current users of the language who hold mistaken mental models of the flag’s
> purpose to reexamine their understanding, hopefully for the better.
> >
> > POTENTIAL COMPLICATIONS: The mismatch between amended documentation and
> existing documentation may cause confusion; it should, though, be an
> auspicious confusion that eventually clarifies rather than misleads.
>
> utf8::is_utf8 probably should be renamed too. Anyway, +1 from me.
>
>
Frankly it (and upgrade/downgrade) shouldn't even be in the utf8::
namespace, it's named that for internal reasons not interface reasons.

-Dan

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