isearch - End highlight when no range found #1725
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Fix editor freeze from inifinite loop.
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Background
I started looking into this from: In vi mode :'<,'>s/^/;;/ leads to a crash.
It was a windy road to find this small code change, but I think this has the smallest impact, and works. I learned a lot about vi-mode ex-commands and isearch.
Cause
When using the isearch mode:
*isearch-search-forward-function* = lem:search-forward-regexp, which vi-mode ex-command substitute does, the editor freezes when attempting to highlight regex that evaluates to an empty string. Eg. "^", "$", both can be searched for, but should not highlight anything.This is because in
isearch:highlight-region, for example with "^", the loop searches backward for "^", then the end loop clause searches forward in the line for "^" and does not find it, so it loops infinitely, and causes Lem to freeze. Same with "$", ".*", etc.Fix
Add to the loop end clause, that if after the points have been moved by these above checks, if the mutable moving start-point = end-point still, then end the highlighting loop as there is nothing to highligh.
Testing
I added tests to vi-mode and verified the isearch ones still pass.
Tested myself via vi-mode subs, and verified isearch still works.
Vi-mode "/" and "?" still highlight correctly.