bug#64088: [PATCH] Make project-root for vc projects return an absolute path

[Spencer Baugh <sbaugh@janestreet.com>]

Dmitry Gutov <dmitry@gutov.dev> writes:
> On 15/06/2023 23:48, Spencer Baugh wrote:
>> -          (setq project (list 'vc backend root))
>> +          (setq project (list 'vc backend (expand-file-name root)))
>
> Spec violated or not (like Eli said, abbreviated names are still
> absolute), we should probably try to fix this in another place, so
> that other backends (whatever external ones exist) don't have to worry
> about the distinction.
>
> As you can see, in project-buffers, for example, we call expand-file-name.

OK, how about this?

diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
index ddb033d50f9..b365e195415 100644
--- a/lisp/progmodes/project.el
+++ b/lisp/progmodes/project.el
@@ -1575,7 +1575,10 @@ project-list-file
 
 (defvar project--list 'unset
   "List structure containing root directories of known projects.
-With some possible metadata (to be decided).")
+With some possible metadata (to be decided).
+
+Entries should be canonicalized with `expand-file-name' before
+being added.")
 
 (defun project--read-project-list ()
   "Initialize `project--list' using contents of `project-list-file'."
@@ -1613,7 +1616,7 @@ project-remember-project
 Save the result in `project-list-file' if the list of projects
 has changed, and NO-WRITE is nil."
   (project--ensure-read-project-list)
-  (let ((dir (project-root pr)))
+  (let ((dir (expand-file-name (project-root pr))))
     (unless (equal (caar project--list) dir)
       (dolist (ent project--list)
         (when (equal dir (car ent))
@@ -1629,7 +1632,7 @@ project--remove-from-project-list
 from the list using REPORT-MESSAGE, which is a format string
 passed to `message' as its first argument."
   (project--ensure-read-project-list)
-  (when-let ((ent (assoc project-root project--list)))
+  (when-let ((ent (assoc (expand-file-name project-root) project--list)))
     (setq project--list (delq ent project--list))
     (message report-message project-root)
     (project--write-project-list)))