bug#63829: 29.0.90; project-find-file's future history breaks with common-parent-directory

[Dmitry Gutov]

On 15/08/2023 01:47, sbaugh@catern.com wrote:

> > > > I'm not sure I understand the alternative - the idea would be to share
> > > > project file name history between all projects?  I guess that could be
> > > > nice, although I don't personally use file name history that much, and
> > > > AFAIK it wouldn't solve any concrete user problems, so I'm not really
> > > > motivated to implement it.
> > >
> > > The alternative is a little more general, e.g. propertize every such
> > > history entry with the value of the root, so that they can be
> > > post-processed to adapt to any other root directory.
> > >
> > > This shouldn't take too much work, actually. But I don't know if that
> > > is indeed a necessary feature. From the discussion
> > > (https://debbugs.gnu.org/58447), I had been under impression that it
> > > would be wanted, but it might be just "nice to have".
> >
> > I would be happy to do that.  That sounds very cool actually.
> >
> > Can you elaborate on how exactly you imagine this happening?  I guess,
> > every time someone enters a filename with project-find-file or
> > project-find-dir, we would include a propertized version of that
> > filename in file-name-history?  And then we would re-relativize them and
> > adapt them to the current project when including them as history?
>
> Okay, I did that.  Extremely rough patch follows.

Thanks! It's very close to what I was thinking of (modulo some cosmetics 
and perf optimizations).

> Btw, the reason I'm interested in this shared project history is because
> our workflow involves creating many new projects (one per branch); so
> mostly each project has no history at all, and sharing history between
> projects is the only way to get any.

Now that you can have this additional capability as an option, do you 
think you will be using it as well?

> But, it seems to me that this doesn't really help with having the
> current file be "future history".  That's still useful when switching
> between similar projects.  And all the logic of my other patch which
> does that, is still required with this patch.

Indeed, that's a good point. So I think we'll install your first patch 
either way.

Before we do that, small (or not so small) question: do you think we 
should test that the current buffer exists in the other project too? We 
could do that with file-exists-p (but that's an extra round-trip over 
Tramp), or by checking against the full list like in below.

Relatedly, with the cross-project history, we should ask the same 
question: will we check that the "transplanted" history entries 
correspond to existing files in the other project (and filter out those 
that don't).

WDYT?

diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
index d8b12c9c880..a32bc2dd8d3 100644
--- a/lisp/progmodes/project.el
+++ b/lisp/progmodes/project.el
@@ -1116,7 +1116,10 @@ project-find-file-in
          (completion-ignore-case read-file-name-completion-ignore-case)
          (file (funcall project-read-file-name-function
                         "Find file" all-files nil 'file-name-history
-                        suggested-filename)))
+                        (if (file-name-absolute-p suggested-filename)
+                            (and (member suggested-filename all-files)
+                                 suggested-filename)
+                          suggested-filename))))
     (if (string= file "")
         (user-error "You didn't specify the file")
       (find-file file))))