feat(skills): add vue-patterns skill for Vue.js 3 best practices

Add skills/vue-patterns/SKILL.md covering: - Project structure (feature-first layout, file naming) - Component architecture (SFC order, presentational vs container, props/emits) - Composables (use prefix, MaybeRef/toValue, cleanup, vs mixins) - State management decision tree (local → props → provide/inject → Pinia → server state) - Vue Router patterns (lazy loading, navigation guards, reactive params) - Template patterns (v-if/v-else, v-show, v-for, v-model with defineModel) - Performance techniques (shallowRef, v-memo, v-once, KeepAlive, Suspense) - Testing stack and patterns (Vitest, Vue Test Utils, Pinia testing) - Nuxt-specific patterns (auto-imports, useAsyncData, server routes, runtime config) - Vue 3.5+ new APIs section: reactive props destructure, useTemplateRef, onWatcherCleanup, useId, defer Teleport, lazy hydration - Anti-patterns table with Vue 3.5+ version-specific notes
2026-06-16 08:26:52 +08:00 · 2026-06-12 17:54:28 +08:00 · 2026-06-12 17:54:28 +08:00 · fe2d6656a3
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+---
+name: vue-patterns
+description: Vue.js 3 Composition API patterns, component architecture, reactivity best practices, Pinia state management, Vue Router navigation, and Nuxt SSR patterns. Activates for Vue, Nuxt, Vite, or Pinia projects.
+origin: ECC
+---
+
+# Vue.js Patterns and Best Practices
+
+Comprehensive guide for Vue.js 3 development using Composition API (`<script setup>`), covering component design, reactivity, state management, routing, testing, and SSR patterns. Nuxt-specific guidance is included where it differs from vanilla Vue.
+
+## When to Activate
+
+Activate this skill when:
+- The project uses Vue.js (any version), Nuxt, Vite + Vue, or Pinia.
+- The user asks about Vue component architecture, composables, reactivity, or state management.
+- Reviewing Vue Single-File Components (`.vue` files).
+- Setting up Vue Router, Pinia stores, or Vite/Vitest configuration.
+- Discussing Vue-specific performance, security, or SSR patterns.
+
+---
+
+## 1. Project Structure
+
+### Recommended Layout (Feature-First)
+
+```
+src/
+├── api/              # API client and endpoint definitions
+├── assets/           # Static assets (images, fonts, icons)
+├── components/       # Shared/reusable components
+│   ├── base/         # Base UI primitives (Button, Input, Modal)
+│   └── features/     # Feature-specific shared components
+├── composables/      # Reusable Composition API logic
+├── layouts/          # Page layouts (optional)
+├── pages/            # Route-level page components
+├── router/           # Vue Router configuration
+├── stores/           # Pinia stores
+├── types/            # TypeScript type definitions
+├── utils/            # Pure utility functions
+└── App.vue           # Root component
+```
+
+### File Naming
+
+| Convention | When to Use |
+|-----------|-------------|
+| `PascalCase.vue` | All components (enforced by `vue/multi-word-component-names`) |
+| `useCamelCase.ts` | Composables |
+| `camelCase.ts` | Utilities, API clients, types |
+| `kebab-case` directories | Route segments, feature folders |
+
+---
+
+## 2. Component Architecture
+
+### Single-File Component Order
+
+```vue
+<script setup lang="ts">
+// 1. Imports (vue → ecosystem → absolute → relative)
+// 2. Props & Emits & Slots
+// 3. Composables
+// 4. Local state (ref/reactive)
+// 5. Computed properties
+// 6. Methods
+// 7. Watchers
+// 8. Lifecycle hooks
+</script>
+
+<template>
+  <!-- Template content -->
+</template>
+
+<style scoped>
+  /* Scoped styles */
+</style>
+```
+
+### Presentational vs Container
+
+- **Container components**: Own data fetching, state, and side effects. Render presentational components.
+- **Presentational components**: Receive props, emit events. No API calls, no store access. Pure rendering.
+
+### Props Best Practices
+
+```ts
+// Type-based props with defaults
+interface Props {
+  label: string;
+  variant?: "primary" | "secondary";
+  disabled?: boolean;
+  items: Item[];
+}
+
+const props = withDefaults(defineProps<Props>(), {
+  variant: "primary",
+  disabled: false,
+});
+```
+
+- Always provide `type`, and `required`/`default` where appropriate.
+- Boolean props: `isXxx`, `hasXxx`, `canXxx`.
+- Never mutate props — emit events instead.
+- For v-model binding, use `defineModel()` (Vue 3.4+) or `modelValue` + `update:modelValue`.
+
+### Events
+
+```ts
+const emit = defineEmits<{
+  submit: [];
+  "update:modelValue": [value: string];
+  select: [id: string, index: number];
+}>();
+```
+
+- Use kebab-case in templates (`@update:model-value`).
+- Use camelCase in script (`emit("update:modelValue", val)`).
+
+---
+
+## 3. Composables (Reusable Logic)
+
+### Structure
+
+```ts
+// composables/useDebounce.ts
+export function useDebounce<T>(value: MaybeRef<T>, delay: number): Ref<T> {
+  const debounced = ref(toValue(value)) as Ref<T>;
+
+  let timer: ReturnType<typeof setTimeout>;
+  watch(
+    () => toValue(value),
+    (newVal) => {
+      clearTimeout(timer);
+      timer = setTimeout(() => { debounced.value = newVal; }, delay);
+    }
+  );
+
+  onUnmounted(() => clearTimeout(timer));
+  return readonly(debounced);
+}
+```
+
+### Rules
+
+- Must start with `use` prefix.
+- Return reactive values (`ref`, `computed`, `reactive`), never plain primitives.
+- Accept reactive inputs via `MaybeRef` / `toRef()` / `toValue()`.
+- Clean up side effects in `onUnmounted` or watcher `onCleanup`.
+- No module-scope side effects.
+
+### vs Mixins
+
+Composables replace Vue 2 mixins entirely:
+- **Mixins**: Opaque data flow, source-of-truth collisions, name conflicts.
+- **Composables**: Explicit imports, clear return values, composable and tree-shakable.
+
+---
+
+## 4. State Management
+
+### When to Use What
+
+| Pattern | Use Case |
+|---------|----------|
+| `ref()` / `reactive()` | Local component state |
+| Props + Emits | Parent-child communication |
+| Provide / Inject | Theme, config, plugin API |
+| Pinia store | Global, shared, complex state |
+| Server state composable | API data with caching (wrap `fetch`/TanStack Query) |
+
+### Pinia Setup Store (Preferred)
+
+```ts
+// stores/useCartStore.ts
+export const useCartStore = defineStore("cart", () => {
+  const items = ref<CartItem[]>([]);
+  const isLoading = ref(false);
+
+  const totalPrice = computed(() =>
+    items.value.reduce((sum, i) => sum + i.price * i.quantity, 0)
+  );
+  const itemCount = computed(() =>
+    items.value.reduce((sum, i) => sum + i.quantity, 0)
+  );
+
+  async function addItem(productId: string) {
+    isLoading.value = true;
+    try {
+      const item = await fetchProduct(productId);
+      const existing = items.value.find(i => i.id === item.id);
+      if (existing) existing.quantity++;
+      else items.value.push({ ...item, quantity: 1 });
+    } finally {
+      isLoading.value = false;
+    }
+  }
+
+  return { items, isLoading, totalPrice, itemCount, addItem };
+});
+```
+
+- Use Setup Store syntax (not Options Store).
+- Actions: only place to mutate state.
+- Every async action: handle loading + success + error.
+
+---
+
+## 5. Vue Router
+
+### Route Definitions
+
+```ts
+const routes = [
+  {
+    path: "/users/:id",
+    name: "user-detail",
+    component: () => import("@/pages/UserDetail.vue"), // lazy
+    props: true, // pass params as props
+    meta: { requiresAuth: true },
+  },
+];
+```
+
+### Navigation Guards
+
+```ts
+router.beforeEach((to, from) => {
+  const { isLoggedIn } = useAuthStore();
+  if (to.meta.requiresAuth && !isLoggedIn) {
+    return { name: "login", query: { redirect: to.fullPath } };
+  }
+});
+```
+
+### Reactive Route Params
+
+When a component stays mounted but route params change:
+
+```ts
+const route = useRoute();
+const id = computed(() => route.params.id as string);
+watch(id, (newId) => fetchItem(newId));
+```
+
+---
+
+## 6. Template Patterns
+
+### Template Syntax
+
+```vue
+<!-- v-if/v-else-if/v-else -->
+<div v-if="isLoading">Loading...</div>
+<div v-else-if="error">Error: {{ error }}</div>
+<div v-else>{{ content }}</div>
+
+<!-- v-show for frequent toggles -->
+<div v-show="isOpen">Toggled content</div>
+
+<!-- v-for with stable keys -->
+<div v-for="item in items" :key="item.id">{{ item.name }}</div>
+
+<!-- Computed filtered list (not v-if + v-for on same element) -->
+<div v-for="item in activeItems" :key="item.id">{{ item.name }}</div>
+
+<!-- Event handling -->
+<form @submit.prevent="handleSubmit">
+  <button type="submit">Save</button>
+</form>
+
+<!-- v-model -->
+<input v-model="name" />
+<CustomInput v-model="value" v-model:title="title" />
+```
+
+---
+
+## 7. Performance
+
+| Technique | When to Use |
+|-----------|-------------|
+| `v-memo` | List items that rarely change |
+| `v-once` | Content rendered once and static forever |
+| `shallowRef()` | Large data structures replaced wholesale |
+| `shallowReactive()` | Only top-level properties are reactive |
+| `v-show` over `v-if` | Frequent visibility toggles |
+| `<KeepAlive :max="10">` | Cache toggled views |
+| Lazy routes | `() => import(...)` for non-critical routes |
+| `Suspense` | Async component loading with fallback |
+
+---
+
+## 8. Testing
+
+### Stack
+
+- **Vitest** for unit and component tests
+- **Vue Test Utils** for mounting and interaction
+- **@pinia/testing** for store mocking
+- **Playwright** for E2E
+
+### Component Test Pattern
+
+```ts
+import { mount } from "@vue/test-utils";
+import { createPinia, setActivePinia } from "pinia";
+import UserCard from "./UserCard.vue";
+
+beforeEach(() => { setActivePinia(createPinia()); });
+
+it("renders and emits", async () => {
+  const wrapper = mount(UserCard, {
+    props: { user: { id: "1", name: "Alice" } },
+  });
+  expect(wrapper.text()).toContain("Alice");
+  await wrapper.find("button").trigger("click");
+  expect(wrapper.emitted("select")![0]).toEqual(["1"]);
+});
+```
+
+---
+
+## 9. Nuxt-Specific Patterns
+
+### Auto-Imports
+
+Nuxt auto-imports `ref`, `computed`, `watch`, `useFetch`, `useAsyncData`, etc. Use them directly without importing. For non-Nuxt projects, always import explicitly.
+
+### useAsyncData / useFetch
+
+```ts
+const { data: user, pending, error, refresh } = await useAsyncData(
+  "user", // unique key for caching
+  () => $fetch(`/api/users/${id}`),
+);
+
+const { data: posts } = await useFetch("/api/posts", {
+  query: { page: 1 },
+  key: "posts-page-1", // dedupes requests
+});
+```
+
+### Server Routes
+
+```ts
+// server/api/users/[id].ts
+export default defineEventHandler(async (event) => {
+  const { id } = await getValidatedRouterParams(event, z.object({
+    id: z.string().uuid(),
+  }).parse);
+  // ... fetch and return
+});
+```
+
+### Runtime Config
+
+```ts
+// nuxt.config.ts
+export default defineNuxtConfig({
+  runtimeConfig: {
+    // server-only
+    apiSecret: "",
+    // public (exposed to client)
+    public: {
+      apiBase: "https://api.example.com",
+    },
+  },
+});
+```
+
+---
+
+## 10. Vue 3.5+ New APIs
+
+### Reactive Props Destructure
+
+Vue 3.5 stabilized reactive props destructure — destructured variables from `defineProps()` are automatically reactive:
+
+```ts
+// Vue 3.5+: destructured props are reactive (no need for toRefs)
+const { count = 0, msg = "hello" } = defineProps<{
+  count?: number;
+  msg?: string;
+}>();
+
+// Limitation: cannot watch destructured prop directly
+watch(() => count, (newVal) => { ... }); // ✅ getter required
+```
+
+### `useTemplateRef()`
+
+Replace name-matched plain refs with `useTemplateRef()` for template references:
+
+```ts
+import { useTemplateRef } from "vue";
+const inputEl = useTemplateRef<HTMLInputElement>("input");
+// "input" matches the ref="input" attribute in template, not the variable name
+```
+
+Supports dynamic ref IDs: `useTemplateRef(dynamicRefId)`.
+
+### `onWatcherCleanup()`
+
+Globally importable watcher cleanup API (Vue 3.5+):
+
+```ts
+import { watch, onWatcherCleanup } from "vue";
+
+watch(userId, async (newId) => {
+  const controller = new AbortController();
+  onWatcherCleanup(() => controller.abort());
+  // ... fetch with signal
+});
+```
+
+### `useId()`
+
+SSR-stable unique ID generation for form elements and accessibility:
+
+```ts
+import { useId } from "vue";
+const id = useId();
+```
+
+### `defer` Teleport
+
+`<Teleport defer>` allows teleporting to targets rendered in the same cycle:
+
+```vue
+<Teleport defer target="#container">Content</Teleport>
+<div id="container"></div>
+```
+
+### Lazy Hydration (SSR)
+
+`defineAsyncComponent()` now supports `hydrate` strategy:
+
+```ts
+import { defineAsyncComponent, hydrateOnVisible } from "vue";
+const AsyncComp = defineAsyncComponent({
+  loader: () => import("./Comp.vue"),
+  hydrate: hydrateOnVisible(),
+});
+```
+
+---
+
+## Anti-Patterns
+
+| Anti-Pattern | Why It's Wrong | The Fix |
+|-------------|---------------|---------|
+| Destructuring `defineProps()` (Vue < 3.5) | Captures snapshot, loses reactivity | Access via `props.xxx` or use `toRefs()` |
+| `watch()` on destructured prop (Vue 3.5+) | Compile-time error — destructured props can't be watched directly | Use getter wrapper: `watch(() => count, ...)` |
+| `v-if` + `v-for` on same element | Ambiguous execution order | Use computed filtered array |
+| `v-for` key = index | Broken state on reorder | Use stable database IDs |
+| Mutating props | Violates one-way data flow | Emit events or use `v-model` |
+| `v-html` with user content | XSS vulnerability | Sanitize with DOMPurify |
+| Mixins in Vue 3 | Opaque, collision-prone | Replace with composables |
+| Module-scope side effects in composable | Shared across instances | Scope in `onMounted` + `onUnmounted` |
+| `reactive()` for replaceable state | Replacement breaks reactivity | Use `ref()` instead |
+| Watcher without cleanup | Memory leaks, race conditions | Use `onCleanup` or `onWatcherCleanup()` (Vue 3.5+) |
+| Options API in new Vue 3 code | Ecosystem move to Composition API | Use `<script setup>` |
+| Plain ref for template references | No dynamic ref support, name-matching fragile | Use `useTemplateRef()` (Vue 3.5+) |
+
+## Related Skills
+
+- `accessibility` — ARIA, semantic HTML, focus management
+- `frontend-patterns` — Cross-framework frontend architecture
+- `typescript` — TypeScript best practices applied to Vue projects
+- `coding-standards` — General code quality standards