develooper Front page | perl.perl5.porters | Postings from August 2021

Re: Pre-RFC: Rename SVf_UTF8 et al.

Thread Previous | Thread Next
From:
Tomasz Konojacki
Date:
August 18, 2021 19:50
Subject:
Re: Pre-RFC: Rename SVf_UTF8 et al.
Message ID:
20210818214957.93CB.5C4F47F8@xenu.pl
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.


Thread Previous | Thread Next


nntp.perl.org: Perl Programming lists via nntp and http.
Comments to Ask Bjørn Hansen at ask@perl.org | Group listing | About