Re: New feature in project.el: Remembering the previously used projects

[Dmitry Gutov <dgutov@yandex.ru>]

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On 29.05.2020 02:05, Basil L. Contovounesios wrote:

>> Please let us know how you like the change, and if you see any new problems.
> 
> Only one feature request and some minor questions from me.
> 
> Can the project-list file name please be customisable?

Of course. Just an omission.

> Could the contents of the project-list file comprise easily readable,
> printable, and even extensible sexps?
> 
> Could project-switch-project reuse read-multiple-choice or similar?

I'm attaching a patch that makes it use read-multiple-choice, check it 
out. But I'm not sure the result looks better than what we have now.

Suggestions on "similar" welcome.

> Isn't there a race here?
> 
>    (defun project--ensure-file-exists (filename)
>      "Create an empty file FILENAME if it doesn't exist."
>      (unless (file-exists-p filename)
>        (with-temp-buffer
>          (write-file filename))))
> 
> Why not use something like the following instead?
> 
>    (ignore-error file-already-exists
>      (write-region "" nil filename nil 0 nil 'excl))

Looks good to me. Let's see what Simen says.

> In fact, couldn't project--ensure-file-exists be eliminated altogether?
> If the file doesn't exist, just don't set project--list, or set it to
> nil.

Or that.

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diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
index 92293d0e2d..54bacc598e 100644
--- a/lisp/progmodes/project.el
+++ b/lisp/progmodes/project.el
@@ -805,15 +805,11 @@ project-switch-commands
 command to run when KEY is pressed.  LABEL is used to distinguish
 the choice in the dispatch menu.")
 
-(defun project--keymap-prompt ()
-  "Return a prompt for the project swithing dispatch menu."
-  (mapconcat
+(defun project--switch-choices ()
+  (mapcar
    (pcase-lambda (`(,key ,label))
-     (format "[%s] %s"
-             (propertize (key-description `(,key)) 'face 'bold)
-             label))
-   project-switch-commands
-   "  "))
+     (list (aref key 0) label))
+   project-switch-commands))
 
 ;;;###autoload
 (defun project-switch-project ()
@@ -822,17 +818,12 @@ project-switch-project
 and presented in a dispatch menu."
   (interactive)
   (let ((dir (project-prompt-project-dir))
-        (choice nil))
-    (while (not (and choice
-                     (or (equal choice (kbd "C-g"))
-                         (assoc choice project-switch-commands))))
-      (setq choice (read-key-sequence (project--keymap-prompt))))
-    (if (equal choice (kbd "C-g"))
-        (message "Quit")
-      (let ((default-directory dir)
-            (project-current-inhibit-prompt t))
-        (call-interactively
-         (nth 2 (assoc choice project-switch-commands)))))))
+        (choice (read-multiple-choice "Action:"
+                                      (project--switch-choices))))
+    (let ((default-directory dir)
+          (project-current-inhibit-prompt t))
+      (call-interactively
+       (nth 2 (assoc (string choice) project-switch-commands))))))
 
 (provide 'project)
 ;;; project.el ends here