bug#41741: [PATCH] Save project list as lisp data

[Simen Heggestøyl]

Hi.

I'm attaching a suggested patch for changing project.el's project list
format from a line based one to proper Lisp data as discussed in the
"New feature in project.el: Remembering the previously used projects"
thread on emacs-devel.

No metadata is added at this point, but it makes it extensible for the
future.

-- Simen

>From 3084f651d6c0f5e6b4b3ac699b59742f98af2248 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Simen=20Heggest=C3=B8yl?= <simenheg@gmail.com>
Date: Fri, 5 Jun 2020 19:32:30 +0200
Subject: [PATCH] Save project list as lisp data

Save the project list file as lisp data instead of line separated
strings to make it more extendable in the future.

* lisp/progmodes/project.el (project--read-project-list)
(project--write-project-list, project--add-to-project-list-front)
(project--remove-from-project-list): Adjust to `project--list' now
being an alist.
---
 lisp/progmodes/project.el | 25 ++++++++++---------------
 1 file changed, 10 insertions(+), 15 deletions(-)

diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
index 4d57fb25fd..3b007bc8dc 100644
--- a/lisp/progmodes/project.el
+++ b/lisp/progmodes/project.el
@@ -757,19 +757,13 @@ project--list
   "List of known project directories.")
 
 (defun project--read-project-list ()
-  "Initialize `project--list' from the project list file."
+  "Initialize `project--list' from the file `project-list-file'."
   (let ((filename project-list-file))
     (setq project--list
-          (when (file-exists-p filename)
+          (when (file-readable-p filename)
             (with-temp-buffer
               (insert-file-contents filename)
-              (let ((dirs (split-string (buffer-string) "\n" t))
-                    (project-list '()))
-                (dolist (dir dirs)
-                  (cl-pushnew (file-name-as-directory dir)
-                              project-list
-                              :test #'equal))
-                (reverse project-list)))))))
+              (car (read-from-string (buffer-string))))))))
 
 (defun project--ensure-read-project-list ()
   "Initialize `project--list' if it hasn't already been."
@@ -780,7 +774,8 @@ project--write-project-list
   "Persist `project--list' to the project list file."
   (let ((filename project-list-file))
     (with-temp-buffer
-      (insert (string-join project--list "\n"))
+      (insert ";;; -*- lisp-data -*-\n")
+      (pp project--list (current-buffer))
       (write-region nil nil filename nil 'silent))))
 
 (defun project--add-to-project-list-front (pr)
@@ -788,9 +783,9 @@ project--add-to-project-list-front
 Save the result to disk if the project list was changed."
   (project--ensure-read-project-list)
   (let ((dir (project-root pr)))
-    (unless (equal (car project--list) dir)
-      (setq project--list (delete dir project--list))
-      (push dir project--list)
+    (unless (equal (caar project--list) dir)
+      (setq project--list (assoc-delete-all dir project--list))
+      (push (list dir) project--list)
       (project--write-project-list))))
 
 (defun project--remove-from-project-list (pr-dir)
@@ -798,8 +793,8 @@ project--remove-from-project-list
 If the directory was in the list before the removal, save the
 result to disk."
   (project--ensure-read-project-list)
-  (when (member pr-dir project--list)
-    (setq project--list (delete pr-dir project--list))
+  (when (assoc pr-dir project--list)
+    (setq project--list (assoc-delete-all pr-dir project--list))
     (message "Project `%s' not found; removed from list" pr-dir)
     (project--write-project-list)))
 
-- 
2.26.2