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

[Stephen Berman]

On Sat, 28 Nov 2020 20:11:48 +0200 Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Stephen Berman <stephen.berman@gmx.net>
>> Date: Sat, 28 Nov 2020 19:03:17 +0100
>> 
>> 0. echo aä > /tmp/test
>> 1. emacs -Q /tmp/test ; the file encoding is utf-8
>> 2. Type `C-x d RET', mark the file 'test', type `A a RET'
>> => *xref* displays the line 'aä'
>> 3. In buffer 'test' type `C-x RET f iso-8859-1 RET' and then `C-x C-s'
>> 4. Repeat step 2
>> => user-error: No matches for: a
>> 
>> dired-do-find-regexp calls xref-matches-in-files and that calls grep,
>> and that's where the failure happens, so strictly speaking this isn't an
>> Emacs bug, but it is a problem for users of dired-do-find-regexp
>> (dired-do-search and occur, for example, don't have this problem).  One
>> workaround is to add the -a option to the grep invocation in
>> xref-matches-in-files; then the search succeeds and the *xref* buffer
>> displays 'a\344'.  But this doesn't work if 'ä' is the search term.
>
> 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 (but easy enough to wrap a lambda around and bind it to a
key).  Do you then agree to adding -a to the grep invocation in
xref-matches-in-files?  Or could that have undesirable consequences?

Steve Berman