Re: [PG19] psql backslash commands fail with translated messages and a non UTF-8 client encoding

Hi Tom,

> * It occurred to me that we could avoid all the gettext_noop()
> decorations by adding addQueryComment to GETTEXT_TRIGGERS.

Done in v4. The call sites now pass a plain string. The msgids that
xgettext extracts are the same as on master.

> Should we invert the logic to avoid a useless gettext lookup?

Yes. v4 checks the encodings first and calls gettext only when they
match. On Windows it never looks the label up. The one thing we lose
is a translation that happens to be plain ASCII when the encodings
differ.

> * Do we actually need to test for OUTPUT_CHARSET, given that
> this code doesn't execute on Windows?

Yes. glibc honors it too. On Ubuntu 24.04 with glibc 2.39,
a ja_JP.UTF-8 locale and a UTF8 database, an unpatched psql 19 works,
and with OUTPUT_CHARSET=EUC-JP it fails:

ERROR: invalid byte sequence for encoding "UTF8": 0xc2 0xd0

v4 uses the English label in that case.

Thanks,
Shihao