Issue with git-grep

[dpassen]

Recently, dumb-jump has failed to work for me when using the git-grep searcher. If I force ripgrep (setq dumb-jump-force-searcher 'rg), it works as I expect.

git 2.39.0
dumb-jump 20220620.2325
emacs 28.2

[wrightgardner]

I also ran into this with git 2.39.0. After setting debug logging with (setq dumb-jump-debug t) and examining the command, I played with it in a couple versions of git (the only 2 available on my system right now).

With git 2.37.1, git grep -E returns a result.
With git 2.39.0, git grep -E does not return a result.

With git 2.39.0, git grep -P does return a result, but I believe that option needs to be compiled in, so it may not be universally available.

I could not find anything documenting a change in behavior for git grep, but I haven't had a lot of time to look or to examine any other versions.

[wrightgardner]

I had a little more time to look into this. git ships its own version of grep. Somewhere between 2.37 and 2.39, it appears that the handling of the boundary character class changed in its extended regex option. \\b works with GNU grep, but not BSD grep. Replacing \\b with \[\[:\<:\]\] (the BSD boundary), then results come back. Consulting http://mail-index.netbsd.org/tech-userlevel/2012/12/02/msg006954.html, it appears that there is not one form that works across OSs.

Forcing a searcher is ok, unless you're like me and use tramp to edit remote projects on machines that do not have that forced searcher installed. In this case, I'd like to use dumb-jump-prefer-searcher, but git grep is always used when in a git repo and not forcing a searcher.

One possible solution would be to move dumb-jump-prefer-searcher above git-grep here: https://github.com/jacktasia/dumb-jump/blob/master/dumb-jump.el#L2671. In this way, you could set dumb-jump-prefer-searcher to something you do have installed and essentially avoid the issue. However, this could cause a change in behavior for anyone who has it set now and is using git-grep over this preferred searcher.

In very limited experimentation, adding -w to the git grep command and removing \\b from the front of the search string seems to produce similar results with both git versions. I would have to look more into the existing unit tests to see if there is adequate coverage to be confident in such a change. If so, this could be a path forward.

-edited for grammar

[wrightgardner]

Unfortunately, it looks like \b used throughout many of the regular expressions, which would mean that the git grep -w flag won't do the trick because removing \b from the front won't be enough. You'd have to be able replace \b throughout the regular expressions.

[wrightgardner]

I think it may have been this commit that changed the git grep behavior: git/git@1819ad3

It notes changing to use the native regex library, which would account for the change from \b working to requiring BSD style word boundaries.

[wrightgardner]

I also tried moving dumb-jump-prefer-searcher above git grep in preference, but it finds my locally installed rg and is not operating on the remote, so it does not help in my situation with remote hosts.

[gsingh93]

Not sure if it's just the boundary character. \s for whitespace doesn't seem to work either. I'm using git 2.40 on macOS.

I guess we should file a bug in the git repo?

[wrightgardner]

It might be worth a try, but I'm not sure if they'd consider it a bug or not. It's using the grep style native to the platform now. It just wasn't doing that on macOS before. If they're willing to take it on as it changed expected behavior (or at least the precedent set), that would be nice. It would normalize the behavior again across platforms.

Otherwise, It might be possible to detect the git version and the platform and sub the proper character classes in dumb-jump. It's already trying to detect the version and BSD/GNU for grep:

dumb-jump/dumb-jump.el

Line 1835 in ba41273

(defun dumb-jump-grep-installed? ()

And also do some substitution of character classes based on gnu-grep being present:

dumb-jump/dumb-jump.el

Line 2843 in ba41273

(defun dumb-jump-populate-regex (it look-for variant)

[wrightgardner]

There are a couple of related bugs filed with git, but not specifically dealing with extended regex:

Suspected git grep regression in git 2.40.0
git bug: Perl compatible regular expressions do not work as expected

Filing a bug would at least get this on the radar as another side-effect.

[wrightgardner]

I did attempt to file a bug/question with git. I'll provide a link to it once I have one. It would be very nice if they fixed this on their end. Otherwise, it gets a bit complicated to detect the git version and os and sub in all the correct character classes.

[wrightgardner]

Conversation with Git: https://lore.kernel.org/git/[email protected]/T/