[FIX] mail: functions for FieldCommand should return boolean value

The executing function for FieldCommand should return boolean value
to indicate whether the value changed for triggering the re-computation.

closes odoo/odoo#66648

Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>

addons/mail/static/src/model/model_field_command.js

@@ -9,7 +9,9 @@ odoo.define('mail/static/src/model/model_field_command.js', function (require) {
 class FieldCommand {
     /**
      * @constructor
-     * @param {function} func function to call when executing this command
+     * @param {function} func function to call when executing this command. 
+     * The function should ALWAYS return a boolean value 
+     * to indicate whether the value changed.
      */
     constructor(func) {
         this.func = func;
@@ -43,7 +45,7 @@ function clear() {
 function decrement(amount = 1) {
     return new FieldCommand((field, record, options) => {
         const oldValue = field.get(record);
-        field.set(record, oldValue - amount, options);
+        return field.set(record, oldValue - amount, options);
     });
 }
 
@@ -55,7 +57,7 @@ function decrement(amount = 1) {
 function increment(amount = 1) {
     return new FieldCommand((field, record, options) => {
         const oldValue = field.get(record);
-        field.set(record, oldValue + amount, options);
+        return field.set(record, oldValue + amount, options);
     });
 }