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

From: Dmitry Gutov <[email-masked]>
Date: Wed, 16 Aug 2023 04:49:58 +0300

On 15/08/2023 01:47, [email-masked] 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))))