Re: dired-do-find-regexp failure with latin-1 encoding

[Dmitry Gutov <dgutov@yandex.ru>]

On 28.11.2020 21:13, Eli Zaretskii wrote:
>> From: Stephen Berman <stephen.berman@gmx.net>
>> Cc: emacs-devel@gnu.org
>> Date: Sat, 28 Nov 2020 19:46:18 +0100
>>
>>> Does it work for ä if you say
>>>
>>>    C-x RET c latin-1 RET A ä RET
>>>
>>> ?
>>
>> Yes (with -a added to the grep invocation, but not without it).  And
>> then with either 'a' or 'ä' as the search term, *xref* displays 'aä'.
>> So this seems to be the best workaround, though inconvenient for
>> frequent uses
> 
> I really don't see any other way, especially if different files in the
> directory have different encodings.  Grep looks for bytes, not
> characters, and is agnostic to encoding.  And even if we'd do this in
> Emacs Lisp, we'd still need to trust Emacs to guess/detect the correct
> encoding of each file.

Ah, so this way the user explicitly searches for a regexp encoded as 
latin-1?

>> Do you then agree to adding -a to the grep invocation in
>> xref-matches-in-files?  Or could that have undesirable consequences?
> 
> Adding -a probably cannot do any harm, but its support should be
> detected, since I don't think it's portable enough (it isn't in the
> latest Posix spec, at least).

Are you sure about that? Are we sure it won't make searching binary 
files slower, for example?

Also, the manual has this warning:

Warning: The -a option might output  binary  garbage,  which  can  have 
nasty  side effects if the output is a terminal and if the terminal 
driver interprets some of it as commands.

...which might conceivably mess up our parsing of Grep output sometimes?

P.S. Or we can forgo all that and ask the users who want to search for 
non-ASCII strings to install ripgrep. I've posted a patch which adds its 
support a couple of months ago, and I fully intend to resurrect it 
(mostly for performance reasons, though).