Add predicate that determines if the session is saved automatically

README.md

@@ -128,6 +128,17 @@ To set up a minimal environment when easysession creates a new session, you can
 (add-hook 'easysession-new-session-hook #'my-empty-easysession)
 ```
 
+### How can I configure easysession-save-mode to automatically save only the "main" session and let me manually save others?
+
+To set up `easysession-save-mode` to automatically save only the "main" session and allow you to manually save other sessions, add the following code to your configuration:
+```emacs-lisp
+(defun my-easysession-only-main-saved ()
+  "Only save the main session."
+  (when (string= "main" (easysession-get-current-session-name))
+    t))
+(setq easysession-save-mode-predicate 'my-easysession-only-main-saved)
+```
+
 ### How does the author use easysession?
 
 The author uses `easysession.el` by setting up each session to represent a distinct project or a specific "view" on a particular project, including various tabs (built-in tab-bar), window splits, dired buffers, and file editing buffers. This organization allows for the creation of dedicated environments for different tasks or aspects of a project, such as development, debugging, specific issue, and documentation. The author switches between projects and views of the same projects multiple times a day, and `easysession.el` helps significantly by allowing quick transitions between them.

easysession.el

@@ -122,6 +122,23 @@ criteria."
   :type 'function
   :group 'easysession)
 
+(defun easysession--default-auto-save-predicate ()
+  "Default predicate function for `easysession-save-predicate`.
+This function always returns non-nil, ensuring the session is saved."
+  t)
+
+(defcustom
+  easysession-save-mode-predicate #'easysession--default-auto-save-predicate
+  "Predicate that determines if the session is saved automatically.
+This function is called with no arguments and should return non-nil if
+`easysession-save-mode' should save the session automatically. The default
+predicate always returns non-nil, ensuring all sessions are saved
+automatically."
+  :type 'function
+  :group 'easysession)
+
+(defvar easysession--debug nil)
+
 (defvar easysession--timer nil)
 
 (defvar easysession--overwrite-frameset-filter-alist
@@ -856,6 +873,20 @@ initialized."
           (t (easysession--message "Switched to %ssession: %s"
                                    (if new-session "new " "") session-name)))))
 
+(defun easysession--auto-save ()
+  "Save the session automatically based on the auto-save predicate.
+This function is usually called by `easysession-save-mode'. It evaluates the
+`easysession-save-mode-predicate' function, and if the predicate returns
+non-nil, the current session is saved."
+  (interactive)
+  (if (funcall easysession-save-mode-predicate)
+      (easysession-save)
+    (when easysession--debug
+      (easysession--message
+       (concat "[DEBUG] Auto-save ignored: `easysession-save-mode-predicate' "
+               "returned nil."))
+      nil)))
+
 ;;;###autoload
 (define-minor-mode easysession-save-mode
   "Toggle `easysession-save-mode'."
@@ -869,8 +900,8 @@ initialized."
           (setq easysession--timer
 	              (run-with-timer easysession-save-interval
 			                          easysession-save-interval
-                                #'easysession-save)))
-        (add-hook 'kill-emacs-hook #'easysession-save))
+                                #'easysession--auto-save)))
+        (add-hook 'kill-emacs-hook #'easysession--auto-save))
     (when easysession--timer
       (cancel-timer easysession--timer)
       (setq easysession--timer nil))

tests/test-easysession.el

@@ -253,7 +253,22 @@ storing them in respective variables for later use."
     (unless (string= (expand-file-name test-easysession--dired-buffer-path)
                      (expand-file-name default-directory))
       (error
-       "The Dired buffer points to the wrong path"))))
+       "The Dired buffer points to the wrong path")))
+
+  ;; Test save-mode predicate
+  (defun my-easysession-nothing-saved ()
+    "Nothing is saved."
+    nil)
+  (setq easysession-save-mode-predicate 'my-easysession-nothing-saved)
+  (kill-buffer test-easysession--dired-buffer)
+  (easysession--auto-save)
+  (easysession-load)
+  (setq test-easysession--dired-buffer
+        (dired-noselect test-easysession--dired-buffer-path))
+  (when test-easysession--dired-buffer
+    (error (concat "easysession--auto-save or the "
+                   "easysession-save-mode-predicate does not seem to "
+                   "be working"))))
 
 (defun test-easysession--get-all-names ()
   "Test: `easysession--get-all-names'."