feat!: allow set operations on meta

BREAKING CHANGE: if you were setting directly `route.meta` within
`extendRoute()`, you know need to use `route.addToMeta()` instead to
have the same merging behavior. Directly setting `route.meta` now
replaces the `meta` property completely.

src/core/extendRoutes.ts

@@ -93,16 +93,25 @@ export class EditableTreeNode {
   /**
    * Meta property of the route as an object. Note this property is readonly and will be serialized as JSON. It won't contain the meta properties defined with `definePage()` as it could contain expressions **but it does contain the meta properties defined with `<route>` blocks**.
    */
-  get meta() {
+  get meta(): Readonly<RouteMeta> {
     return this.node.metaAsObject
   }
 
   /**
-   * Override the meta property of the route. The passed object will be deeply merged with the existing meta object if any.
-   * Note that the meta property is later on serialized as JSON so you can't pass functions or any other
-   * non-serializable value.
+   * Override the meta property of the route. This will discard any other meta property defined with `<route>` blocks or
+   * through other means.
    */
   set meta(meta: RouteMeta) {
+    this.node.value.removeOverride('meta')
+    this.node.value.setEditOverride('meta', meta)
+  }
+
+  /**
+   * Add meta properties to the route keeping the existing ones. The passed object will be deeply merged with the
+   * existing meta object if any. Note that the meta property is later on serialized as JSON so you can't pass functions
+   * or any other non-serializable value.
+   */
+  addToMeta(meta: Partial<RouteMeta>) {
     this.node.value.addEditOverride({ meta })
   }
 

src/core/treeNodeValue.ts

@@ -129,6 +129,19 @@ class _TreeNodeValueBase {
   addEditOverride(routeBlock: CustomRouteBlock) {
     return this.mergeOverride(EDITS_OVERRIDE_NAME, routeBlock)
   }
+
+  setEditOverride<K extends keyof RouteRecordOverride>(
+    key: K,
+    value: RouteRecordOverride[K]
+  ) {
+    // return this.mergeOverride(EDITS_OVERRIDE_NAME, routeBlock)
+    if (!this._overrides.has(EDITS_OVERRIDE_NAME)) {
+      this._overrides.set(EDITS_OVERRIDE_NAME, {})
+    }
+
+    const existing = this._overrides.get(EDITS_OVERRIDE_NAME)!
+    existing[key] = value
+  }
 }
 
 export class TreeNodeValueStatic extends _TreeNodeValueBase {