projectile-replace stomps regular expressions

[seanfisk]

I'll start with a question, because I'm a little unclear: Is projectile-replace supposed to support regular expressions?

This issue mostly has to do with improvements introduced in #269 by @shosti. projectile-replace uses tags-query-replace, which uses Emacs regular expressions. However, projectile-files-with-string stomps entered regexp under certain conditions.

I'm working on Mac OS X ((projectile-unixy-system-p) → t). I have ag, ack, git grep, and grep (henceforth "grep tools") installed. Under these conditions, ag is selected, and then passed the --literal flag, removing meaning from my regexp query. That's what led me to the problem, but that's not the only issue.

Summary:

• Each of the grep tools has their own interpretation of regular expressions, and
• None of these match how Emacs (i.e., tags-query-replace) interprets them [AFAIK]. Furthermore,
• All of the grep tools can handle literal matches more or less the same, but
• tags-query-replace doesn't support literal matches.

It might be possible to somewhat accurately use the grep tools to speed up literal matches, providing a literal version of tags-query-replace could be created. However, I don't see a clear way that the file list could be narrowed for a regular expression replace without finding a tool that exactly emulates Emacs' regular expressions.

Though filtering files through a faster tool is a significant benefit, it comes at the cost of accuracy. This might not seem to be a big deal, but it's very unexpected when matches you think should be replaced aren't being replaced. In this case, I think accuracy trumps speed.

I'm willing to implement a solution if there is agreement on the desired behavior. Projectile rocks and I love using it! Thanks!

[shosti]

To me, what would make the most sense would be to have two functions, projectile-replace and projectile-replace-regexp. It's unfortunate that tags-query-replace doesn't have a literal matching option, but I think it could be worked around either with some hacking or by escaping special characters in the search string. projectile-replace-regexp would have to use a straight tags-query-replace I think, since the problem of translating Emacs regexps to grep regexps seems much too hard.

[seanfisk]

@shosti Agree completely.

The code for tags-query-replace looks somewhat simple to convert to non-regexp at first glance. query-replace-read-args takes a Boolean regexp-flag which could be passed as nil, and re-search-forward could be changed to search-forward.

[Catalectic]

:+1 for fixing that issue, is there any consensus/interest on supporting regexps across all grep tools for projectile-replace?

[seanfisk]

@Catalectic It's probably possible but I'm not sure it's practical. The problem is that almost all regexp tools have their own subtle differences.

Possibly check out https://github.com/joddie/pcre2el.

[d12frosted]

Any updates in this issue? Or maybe any alternatives? :) Better to have not very sufficient method for projectile-replace-regexp than not having it at all.

[seanfisk]

@d12frosted I don't think anybody has really worked on it. Seeing this again, though, it does bother me that I still can't reliably replace by regexp. I may try to throw together a PR soon. I'll keep this thread updated.