bug#50240: 28.0.50; incorrect handling of ignore files in project-files

[Dmitry Gutov]

Hi!

On 28.08.2021 19:52, Omar Polo wrote:
> Hello,
>
> I'm working on a custom VC backend and noticed something strange
> regarding the handling of ignore files in project-files: ignoring a file
> that has the same name of the project makes project-files return nil.
>
> To reproduce:
>
> 1. create a directory structure as follows:
>
>         mkdir /tmp/foo
>         touch /tmp/foo/{foo,bar}
>
> 2. define a trivial project:
>
>         (cl-defmethod project-roots ((_ (eql foo)))
>           '("/tmp/foo/"))
>
>         (cl-defmethod project-ignores ((_ (eql foo)) _)
>           '("foo"))
>
> 3. invoke project-files
>
>         (project-files 'foo)
>         ;; => nil

> This is because project--files-in-directory directory-file-name.  The
> find command build is
>
>         find -H /tmp/foo \( -path \*/foo \) -prune -o  -type f  -print0
>
> and no files are found because are all pruned.

It might be doing the correct thing, depending on how we define the 
exact semantics of ignores. I guess it will really depend on how this is 
going to be to fix without breaking the previous advancements. ;-)

Try returning "./foo" instead of "foo". Would that work for you? Or does 
your usage require a more general fix?

> If I edit project--files-in-directory to use file-name-as-directory,
> then the command becomes
>
>         find -H /tmp/foo/ \( -path \*/foo \) -prune -o  -type f  -print0
>         # note the final slash!
>
> and project-files successfully returns the files
>
>         (project-files 'foo)
>         ;; => ("/tmp/foo/bar")
>
>  From what I see, project.el used to call file-name-as-directory, but was
> changed to directory-file-name due to bug#48471 (which I can't reproduce
> with OpenBSD find.)

Yeah, for all I know it only happens with 'find' distributed with macOS. 
Which is unfortunate, since it's a relatively popular OS.

> NB: This is can't be reproduced using a vc-git or vc-hg backed project
> because project-files treats those backend specially.

Correct.