[Rd] localeToCharset()

[Tomas Kalibera]

Hi Andreas,

is there still any higher-level problem left you need to solve? Ideally 
one wouldn't need to query what is the native encoding, but directly use 
iconv() or indirectly other R functions to convert the data from/to the 
native encoding. iconv() will find out internally what is the native 
encoding (via data that is available also by l10n_info(), but with care 
for differences between OSes).

Best
Tomas

On 1/31/22 12:38, Blätte, Andreas wrote:
> Dear Ivan,
>
> this is a very helpful explanation!  I think it is important to make output of localeToCharset() more predictable. My problem is essentially not to set the locale such that things will work after all. I think the problem is that you see unexpected results.  I guess I owe a suggestion how to improve the code, but your suggestion looks like a very good starting point.
>
> Andreas
>
> Am 31.01.22, 12:32 schrieb "Ivan Krylov" <krylov.r00t using gmail.com>:
>
>      On Mon, 31 Jan 2022 09:56:27 +0000
>      "Blätte, Andreas" <andreas.blaette using uni-due.de> wrote:
>
>      > After starting R with a re-defined locale (`env LC_CTYPE=en_US.UTF-8
>      > R`,  the output of `localeToCharset()` is:
>      > [1] "UTF-8"     "ISO8859-1"
>
>      > why ISO8859-1 might be a fallback option here?
>
>      ISO8859-1 seems to be offered because it covers the alphabet of
>      American English. Obviously, this doesn't guarantee that the guess is
>      correct. For example, I could symlink the ru_RU.KOI8-R locale on my
>      system to name it "ru_RU", and localeToCharset() would return
>      "ISO8859-5", not knowing the correct answer. їЯавЯг, anyone?
>
>      > Part of my analysis of the code of `localeToCharset()` is that it
>      > targets special scenarios on Windows and macOS, but not on Linux.
>
>      Well, it almost does the right thing. GNU/Linux locales are typically
>      named like <language>_<country>.<encoding>, and localeToCharset()
>      respects the <encoding> part, but only if the language and the country
>      are specified. A quick fix for that would be to add one final case:
>
>      Index: src/library/utils/R/iconv.R
>      ===================================================================
>      --- src/library/utils/R/iconv.R (revision 81596)
>      +++ src/library/utils/R/iconv.R (working copy)
>      @@ -135,6 +135,7 @@
>                   if(enc == "utf8") return(c("UTF-8", guess(ll)))
>                   else return(guess(ll))
>               }
>      +        if (enc == "utf8") return("UTF-8") # fallback for ???.UTF-8
>               return(NA_character_)
>           }
>       }
>
>      (Non-UTF-8 encodings on POSIX are handled above, in the if(nzchar(enc)
>      && enc != "utf8") branch.)
>
>      Maybe a better fix would be to restructure the code a bit, to always
>      take the encoding hint and then also try to guess if the locale looks
>      like it provides a language code.
>
>      --
>      Best regards,
>      Ivan
>
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