refactor: generalize unmount state reset via unmountConfigs (#8813)

Author: tobiu

apps/portal/view/news/TabContainer.mjs

@@ -63,9 +63,11 @@ class NewsTabContainer extends TabContainer {
             }
         }],
         /**
-         * @member {Boolean} resetActiveIndexOnUnmount=true
+         * @member {Object} unmountConfigs={activeIndex: null}
          */
-        resetActiveIndexOnUnmount: true
+        unmountConfigs: {
+            activeIndex: null
+        }
     }
 }
 

src/component/Abstract.mjs

@@ -6,6 +6,7 @@ import Observable       from '../core/Observable.mjs';
 import VdomLifecycle    from '../mixin/VdomLifecycle.mjs';
 import VDomUpdate       from '../manager/VDomUpdate.mjs';
 import VNodeUtil        from '../util/VNode.mjs';
+import {isDescriptor}   from '../core/ConfigSymbols.mjs';
 
 const
     closestController   = Symbol.for('closestController'),
@@ -110,6 +111,17 @@ class Abstract extends Base {
          * @reactive
          */
         stateProvider_: null,
+        /**
+         * A map of config names and values to reset to when the component unmounts.
+         * @member {Object|null} unmountConfigs_={[isDescriptor]:true,merge:'deep',value:null}
+         * @example {activeIndex: null, value: ''}
+         * @reactive
+         */
+        unmountConfigs_: {
+            [isDescriptor]: true,
+            merge         : 'deep',
+            value         : null
+        },
         /**
          * The custom windowIs (timestamp) this component belongs to
          * @member {Number|null} windowId_=null
@@ -229,7 +241,11 @@ class Abstract extends Base {
                 // upon mount, preventing deadlocks where code awaits a VDOM update that effectively already happened.
                 VDomUpdate.executeCallbacks(me.id)
             } else { // unmount
-                delete me._mountedPromise
+                delete me._mountedPromise;
+
+                if (me.unmountConfigs) {
+                    me.set(me.unmountConfigs)
+                }
             }
         }
     }

src/tab/Container.mjs

@@ -95,13 +95,6 @@ class Container extends BaseContainer {
          * @member {Boolean} removeInactiveCards=true
          */
         removeInactiveCards: true,
-        /**
-         * If true, the activeIndex will be reset to null when the component is unmounted.
-         * This is useful for router-driven tab containers to prevent "phantom mounts"
-         * of the previous state before the router updates the active index.
-         * @member {Boolean} resetActiveIndexOnUnmount=false
-         */
-        resetActiveIndexOnUnmount: false,
         /**
          * @member {String|null} tabBarId=null
          */
@@ -204,18 +197,6 @@ class Container extends BaseContainer {
         }
     }
 
-    /**
-     * @param {Boolean} value
-     * @param {Boolean} oldValue
-     */
-    afterSetMounted(value, oldValue) {
-        super.afterSetMounted(value, oldValue);
-
-        if (!value && this.resetActiveIndexOnUnmount) {
-            this.activeIndex = null
-        }
-    }
-
     /**
      * Adjusts the container's layout and CSS classes when the tab bar position changes.
      * This method ensures that the `HeaderToolbar` is docked correctly and that the overall