bug#61668: Bug in flymake-proc with fix

[Camden Narzt]

Hi João,

Yeah I don’t use flymake-proc directly, I think lsp-mode is using it or 
something. Anyway I’ve attached a patch.

flymake-proc.patch
Description: Binary data

Cheers,

Camden


> On Feb 21, 2023, at 5:42 AM, João Távora <joaotavora@gmail.com> wrote:
> 
> Hi Camden,
> 
> Flymake-proc is a deprecated part of Flymake.  I haven't used or tested
> it in a long time (there were never automated tests for it).  When I
> redesigned Flymake years ago, in which flymake-proc became another
> backend, I tested some basic use cases, but I didn't change the
> underlying code, including the directory calculating parts and helpers.
> 
> In other words, this is not "my code" and I never understood it.
> 
> So if you think the change makes sense, go for it i.e. provide a patch
> that we can push. I think there are very few users of this backend
> anyway.
> 
> João
> 
> On Tue, Feb 21, 2023 at 12:35 PM Eli Zaretskii <eliz@gnu.org> wrote:
>> 
>> Adding João.
>> 
>>> Date: Mon, 20 Feb 2023 11:23:02 -0700
>>> From:  Camden Narzt via "Bug reports for GNU Emacs,
>>> the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
>>> 
>>> I’m sorry if this is not the correct place to report a flymake-proc bug, 
>>> but since flymake is included in the emacs git repo I figured it might be 
>>> ok.
>>> 
>>> I’m currently seeing incorrect behaviour from the 
>>> `flymake-proc--delete-temp-directory` function. The path is parsed and then 
>>> reassembled incorrectly as the following backtrace extract demonstrates:
>>> 
>>> flymake-proc--safe-delete-directory("/private/var/folders/p7/03_g5t611499lmjqhwc5tljr0000gn/T/000gn/T/Users/camdennarzt/Developer/Java/getargv.java/src/main/java/cam/narzt/getargv")
>>> flymake-proc--delete-temp-directory("/private/var/folders/p7/03_g5t611499lmjqhwc5tljr0000gn/T/Users/camdennarzt/Developer/Java/getargv.java/src/main/java/cam/narzt/getargv/“)
>>> 
>>> As you can see the `000gn/T/` segment of the path gets duplicated when 
>>> `flymake-proc--safe-delete-directory` gets called.
>>> 
>>> This is because in `flymake-proc--delete-temp-directory` when the `suffix` 
>>> variable is declared it is assumed that `(directory-file-name 
>>> temporary-file-directory)` is a prefix of the `dir-name` argument, however 
>>> `(directory-file-name temporary-file-directory)` doesn’t seem to resolve 
>>> symlinks in the path whereas `dir-name` seems to have symlinks already 
>>> resolved, so they don’t necessarily match. On my system the difference is:
>>> 
>>> (directory-file-name temporary-file-directory) → 
>>> "/var/folders/p7/03_g5t611499lmjqhwc5tljr0000gn/T”
>>> dir-name → 
>>> "/private/var/folders/p7/03_g5t611499lmjqhwc5tljr0000gn/T/Users/camdennarzt/Developer/Java/getargv.java/src/main/java/cam/narzt/getargv/“
>>> 
>>> Note the "/private” prefix on the `dir-name` path. That difference in 
>>> length causes the suffix to be incorrectly determined and then causes a 
>>> bunch of errors while any subsequent function call tries to work with a 
>>> path with the `000gn/T/` segment duplicated which obviously doesn’t exist 
>>> in the fs.
>>> 
>>> Changing the suffix variable to be computed as follows fixes the bug:
>>> 
>>> (substring dir-name (1+ (length (file-truename (expand-file-name 
>>> (directory-file-name temp-dir))))))
>>> 
>>> 
>>> If this can be fixed that’s great, if there’s somewhere else I should 
>>> report this I’d love to know.
>>> 
>>> Cheers,
>>> 
>>> Camden Narzt
>>> 
>>> 
>>> 
> 
> 
> 
> -- 
> João Távora