bug#51011: [PATCH] sort: --debug: add warnings about radix and grouping chars

[Pádraig Brady]

On 11/10/2021 02:54, Pádraig Brady wrote:
> On 11/10/2021 00:34, Paul Eggert wrote:
> > The warnings look good, except that this one:
> >
> > >      $ printf '1.0\n0.9\n' | sort -s -k1,1g --debug
> > >      sort: numbers use ‘.’ as a decimal point in this locale
> > >      0.9
> > >      ___
> > >      1.0
> > >      ___
> >
> > seems overkill if we're in the C locale.
> >
> > Also, shouldn't similar diagnostics be generated if the field separator
> > is '-', or '+', or a digit in the current locale?
>
> Yes this is more informational than a warning.
> As Bernhard mentioned it may be useful to tag
> --debug messages as informational or warnings.
>
> In this case it would be info:
> but would change to warn: if (tab == decimal_point).
>
> The reason for the info message is that it may not
> be obvious to users that numeric comparison
> depends on locale just like text,
> and we already provide the informational
> text comparison message indicating the current locale.
> We would only show this info: message if doing numeric sorting.

Addressing your '+' and '-' comment.
Yes they may also be used as field separators and
so are worth explicitly warning about.

Re warning about using digits in --field-separator,
that would be extremely edge case, and anyway
the --debug key marking should make it apparent
the extent of the numbers being compared.
The same argument can be made for other characters possible in numbers like;
  1E+4 nan, Infinity, 0xabcde.fp-3, etc.

As a related issue, I also thought it appropriate to warn
when we're ignoring multi-byte grouping chars in the locale.

The new warnings in this update are:

  $ LC_ALL=fr_FR.utf8 sort -n --debug /dev/null
  sort: the multi-byte number group separator in this locale is not supported

  $ sort --debug -t- -k1n /dev/null
  sort: key 1 is numeric and spans multiple fields
  sort: field separator ‘-’ is treated as a minus sign in numbers

  $ sort --debug -t+ -k1g /dev/null
  sort: key 1 is numeric and spans multiple fields
  sort: field separator ‘+’ is treated as a plus sign in numbers

I'll apply this later.

cheers,
Pádraig

sort--debug-number-span.patch
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