bug#14729: 24.3.50; Isearch oddity

[Dani Moncayo <dmoncayo@gmail.com>]

On Sat, Jun 29, 2013 at 11:53 PM, Juri Linkov <juri@jurta.org> wrote:
>> I expect that the fontification of the echo area reflects what is
>> happening: that the whole search string ("buffer") is unmatched (not
>> only the last "fer"), since the current search begins just after the
>> last instance of "buf" in the buffer [1], and there is no match
>> (neither full nor partial) of the current search string between that
>> location and the end of the buffer.
>
> `isearch-fail-pos' assumes that in a failed state of search
> a shorter previous successful search string should be taken
> as a basis for highlighting.  In this case, the last successful match
> was "buf", so an appended suffix is highlighted as failed.

Then the mistake is not re-setting that "last successful match" after
each "C-s", because here, the last successful match was "buf" only
after doing "M-< C-s buf" and also after the subsequent "C-s", but
once you type the third "C-s", the whole search string ("buf") is
unmatched (because the search now begins at [1]), and that fact (fully
unmatched search string) cannot change by appending more characters to
the search string.

IOW: After the third "C-s", the search goes from [1] to the end of the
buffer, and therefore any search string starting with a character
different from "f", "e", "r", "." or whitespace will be fully
unmatched, and should be highlighted as such in the echo area.

-----------------------
[1] Position between "buf" and "fer" in the last instance of the
string "buffer".

--
Dani Moncayo