fix: add null check for plugin install method

Add early validation for app parameter to prevent TypeError when accessing properties of null/undefined values and ensure consistent error messages.

Author: lzxb

packages/router-vue/src/index.test.ts

@@ -25,6 +25,16 @@ describe('index.ts - Package Entry Point', () => {
             expect(RouterVueModule.useLink).toBeDefined();
             expect(typeof RouterVueModule.useLink).toBe('function');
         });
+
+        it('should export useRouterViewDepth function', () => {
+            expect(RouterVueModule.useRouterViewDepth).toBeDefined();
+            expect(typeof RouterVueModule.useRouterViewDepth).toBe('function');
+        });
+
+        it('should export getRouterViewDepth function', () => {
+            expect(RouterVueModule.getRouterViewDepth).toBeDefined();
+            expect(typeof RouterVueModule.getRouterViewDepth).toBe('function');
+        });
     });
 
     describe('Options API Exports', () => {
@@ -74,6 +84,7 @@ describe('index.ts - Package Entry Point', () => {
                 'useProvideRouter',
                 'useLink',
                 'useRouterViewDepth',
+                'getRouterViewDepth',
                 // Options API
                 'getRouter',
                 'getRoute',
@@ -100,6 +111,7 @@ describe('index.ts - Package Entry Point', () => {
                 'useProvideRouter',
                 'useLink',
                 'useRouterViewDepth',
+                'getRouterViewDepth',
                 'getRouter',
                 'getRoute',
                 'RouterLink',
@@ -217,6 +229,8 @@ describe('index.ts - Package Entry Point', () => {
                 'useRoute',
                 'useProvideRouter',
                 'useLink',
+                'useRouterViewDepth',
+                'getRouterViewDepth',
                 'getRouter',
                 'getRoute'
             ];

packages/router-vue/src/index.ts

@@ -7,6 +7,7 @@ export {
     useProvideRouter,
     useLink,
     useRouterViewDepth,
+    getRouterViewDepth,
     getRoute,
     getRouter
 } from './use';

packages/router-vue/src/plugin.ts

@@ -71,6 +71,10 @@ export const RouterPlugin = {
      * @param app Vue application instance (Vue 3) or Vue constructor (Vue 2)
      */
     install(app: unknown): void {
+        if (!app) {
+            throw new Error('[@esmx/router-vue] Invalid Vue app instance');
+        }
+
         const vueApp = app as VueApp;
         const target = vueApp.config?.globalProperties || vueApp.prototype;