svelte5-runes-static

使用 adapter-static 的 Svelte 5 Runes（SvelteKit）

概述

使用 Svelte 5 runes 构建静态优先的 SvelteKit 应用，同时避免破坏水合。使用 adapter-static（预渲染）并将全局 store 与组件局部 runes 结合时，请采用这些模式。

相关技能

• svelte（Svelte 5 runes 核心模式）
• sveltekit（适配器、部署、SSR/SSG 模式）
• typescript-core（TypeScript 模式与验证）
• vitest（单元测试模式）

核心专业知识

使用 runes 模式构建静态优先的 Svelte 5 应用，并采用能够在预渲染和水合后正常工作的状态管理模式。

关键兼容性规则

❌ 绝对不要：在 adapter-static 中于模块作用域使用 Runes

问题：静态预渲染后，runes 无法正常水合

// ❌ BROKEN - State becomes frozen after SSG
export function createStore() {
  let state = $state({ count: 0 });
  return {
    get count() { return state.count; },
    increment: () => { state.count++; }
  };
}

失败原因：

• adapter-static 会将组件预渲染为 HTML
• 模块作用域中的 runes 无法序列化／反序列化
• 水合后状态会变为不活跃／冻结
• 响应性会完全失效

解决方案：使用传统的 writable() store 管理全局状态

// ✅ WORKS - Traditional stores hydrate correctly
import { writable } from 'svelte/store';

export function createStore() {
  const count = writable(0);
  return {
    count,
    increment: () => count.update(n => n + 1)
  };
}

❌ 绝对不要：在 $derived 内使用 $ 自动订阅

问题：runes 模式会禁用 $ 自动订阅语法

// ❌ BROKEN - Can't use $ inside $derived
let filtered = $derived($events.filter(e => e.type === 'info'));
//                      ^^^^^^^ Error: $ not available in runes mode

解决方案：在 $effect() 中订阅 → 更新 $state() → 在 $derived() 中使用

// ✅ WORKS - Manual subscription pattern
import { type Writable } from 'svelte/store';

let events = $state<Event[]>([]);

$effect(() => {
  const unsub = eventsStore.subscribe(value => {
    events = value;
  });
  return unsub;
});

let filtered = $derived(events.filter(e => e.type === 'info'));

❌ 绝对不要：使用带 getter 的 Store 工厂

问题：getter 不会建立响应式连接

// ❌ BROKEN - Getter pattern breaks reactivity
export function createSocketStore() {
  const socket = writable<Socket | null>(null);
  return {
    get socket() { return socket; }, // ❌ Not reactive
    connect: () => { /* ... */ }
  };
}

解决方案：直接导出 store

// ✅ WORKS - Direct store exports
export function createSocketStore() {
  const socket = writable<Socket | null>(null);
  const isConnected = derived(socket, $s => $s?.connected ?? false);

  return {
    socket,          // ✅ Direct store reference
    isConnected,     // ✅ Direct derived reference
    connect: () => { /* ... */ }
  };
}

推荐的混合模式

全局状态：传统 Store

对于需要在 SSG/SSR 中保留的状态，使用 writable()/derived()：

// stores/globalState.ts
import { writable, derived } from 'svelte/store';

export const user = writable<User | null>(null);
export const theme = writable<'light' | 'dark'>('light');
export const isAuthenticated = derived(user, $u => $u !== null);

组件状态：Svelte 5 Runes

使用 runes 管理组件局部状态和逻辑：

<script lang="ts">
import { user } from '$lib/stores/globalState';

// Props with runes
let {
  initialCount = 0,
  onUpdate = () => {}
}: {
  initialCount?: number;
  onUpdate?: (count: number) => void;
} = $props();

// Bridge: Store → Rune State
let currentUser = $state<User | null>(null);
$effect(() => {
  const unsub = user.subscribe(u => {
    currentUser = u;
  });
  return unsub;
});

// Component-local state
let count = $state(initialCount);
let doubled = $derived(count * 2);

// Effects
$effect(() => {
  if (count > 10) {
    onUpdate(count);
  }
});

function increment() {
  count++;
}
</script>

<button onclick={increment}>
  {currentUser?.name ?? 'Guest'}: {count} (×2 = {doubled})
</button>

完整的桥接模式

Store → Rune → Derived 链

<script lang="ts">
import { type Writable } from 'svelte/store';

// 1. Import global stores (traditional)
const { events: eventsStore, filters: filtersStore } = myGlobalStore;

// 2. Bridge to rune state
let events = $state<Event[]>([]);
let activeFilters = $state<string[]>([]);

$effect(() => {
  const unsubEvents = eventsStore.subscribe(v => { events = v; });
  const unsubFilters = filtersStore.subscribe(v => { activeFilters = v; });

  return () => {
    unsubEvents();
    unsubFilters();
  };
});

// 3. Derived computations (pure runes)
let filtered = $derived(
  events.filter(e =>
    activeFilters.length === 0 ||
    activeFilters.includes(e.category)
  )
);

let count = $derived(filtered.length);
let hasEvents = $derived(count > 0);
</script>

{#if hasEvents}
  <p>Found {count} events</p>
  {#each filtered as event}
    <EventCard {event} />
  {/each}
{:else}
  <p>No events match filters</p>
{/if}

SSG/SSR 注意事项

预渲染安全模式

// ✅ Safe for prerendering
export const load = async ({ fetch }) => {
  const data = await fetch('/api/data').then(r => r.json());
  return { data };
};

<script lang="ts">
import { browser } from '$app/environment';

let { data } = $props();

// ✅ Client-only initialization
$effect(() => {
  if (browser) {
    // WebSocket, localStorage, etc.
    initializeClientOnlyFeatures();
  }
});
</script>

防止水合不匹配

// ✅ Avoid hydration mismatches
let timestamp = $state<number | null>(null);

$effect(() => {
  if (browser) {
    timestamp = Date.now(); // Only set on client
  }
});

{#if browser}
  <LiveClock />
{:else}
  <p>Loading clock...</p>
{/if}

TypeScript 集成

使用 Runes 的类型化 Props

<script lang="ts">
import type { Snippet } from 'svelte';

interface Props {
  title: string;
  count?: number;
  items: Array<{ id: string; name: string }>;
  onSelect?: (id: string) => void;
  children?: Snippet;
}

let {
  title,
  count = 0,
  items,
  onSelect = () => {},
  children
}: Props = $props();

let selected = $state<string | null>(null);
let filteredItems = $derived(
  items.filter(item =>
    selected === null || item.id === selected
  )
);
</script>

<h2>{title} ({count})</h2>

{#each filteredItems as item}
  <button onclick={() => onSelect(item.id)}>
    {item.name}
  </button>
{/each}

{@render children?.()}

类型化 Store 桥接

<script lang="ts">
import type { Writable, Readable } from 'svelte/store';

interface StoreShape {
  data: Writable<string[]>;
  status: Readable<'loading' | 'ready' | 'error'>;
}

const stores: StoreShape = getMyStores();

let data = $state<string[]>([]);
let status = $state<'loading' | 'ready' | 'error'>('loading');

$effect(() => {
  const unsubData = stores.data.subscribe(v => { data = v; });
  const unsubStatus = stores.status.subscribe(v => { status = v; });
  return () => {
    unsubData();
    unsubStatus();
  };
});

let isEmpty = $derived(data.length === 0);
let isReady = $derived(status === 'ready');
</script>

常见模式

可绑定的组件状态

<script lang="ts">
let {
  value = $bindable(''),
  disabled = false
}: {
  value?: string;
  disabled?: boolean;
} = $props();

let focused = $state(false);
let charCount = $derived(value.length);
let isValid = $derived(charCount >= 3 && charCount <= 100);
</script>

<input
  bind:value
  {disabled}
  onfocus={() => { focused = true; }}
  onblur={() => { focused = false; }}
  class:focused
  class:invalid={!isValid}
/>
<p>{charCount}/100</p>

表单状态管理

<script lang="ts">
interface FormData {
  email: string;
  password: string;
}

let formData = $state<FormData>({
  email: '',
  password: ''
});

let errors = $state<Partial<Record<keyof FormData, string>>>({});

let isValid = $derived(
  formData.email.includes('@') &&
  formData.password.length >= 8
);

let canSubmit = $derived(
  isValid && Object.keys(errors).length === 0
);

function validate(field: keyof FormData) {
  if (field === 'email' && !formData.email.includes('@')) {
    errors.email = 'Invalid email';
  } else if (field === 'password' && formData.password.length < 8) {
    errors.password = 'Password too short';
  } else {
    delete errors[field];
  }
}

async function handleSubmit() {
  if (!canSubmit) return;

  // Submit logic
  const result = await submitForm(formData);

  if (result.ok) {
    // Success
  } else {
    errors = result.errors;
  }
}
</script>

<form onsubmit={handleSubmit}>
  <input
    type="email"
    bind:value={formData.email}
    onblur={() => validate('email')}
  />
  {#if errors.email}
    <span class="error">{errors.email}</span>
  {/if}

  <input
    type="password"
    bind:value={formData.password}
    onblur={() => validate('password')}
  />
  {#if errors.password}
    <span class="error">{errors.password}</span>
  {/if}

  <button type="submit" disabled={!canSubmit}>
    Submit
  </button>
</form>

防抖搜索

<script lang="ts">
import { writable, derived } from 'svelte/store';

const searchQuery = writable('');

// Traditional derived store with debounce
const debouncedQuery = derived(
  searchQuery,
  ($query, set) => {
    const timeout = setTimeout(() => set($query), 300);
    return () => clearTimeout(timeout);
  },
  '' // initial value
);

// Bridge to rune state
let query = $state('');
let debouncedValue = $state('');

$effect(() => {
  searchQuery.set(query);
});

$effect(() => {
  const unsub = debouncedQuery.subscribe(v => {
    debouncedValue = v;
  });
  return unsub;
});

// Use in derived
let results = $derived(
  debouncedValue.length >= 3
    ? performSearch(debouncedValue)
    : []
);
</script>

<input
  type="search"
  bind:value={query}
  placeholder="Search..."
/>

{#each results as result}
  <SearchResult {result} />
{/each}

迁移检查清单

从 Svelte 4 迁移到使用 adapter-static 的 Svelte 5 时：

• 将组件级 $: 替换为 $derived()
• 将 export let prop 替换为 let { prop } = $props()
• 将全局 store 保留为 writable()/derived()
• 为 store → rune 状态添加桥接模式
• 将 $store 语法替换为在 $effect() 中手动订阅
• 使用 npm run build 测试预渲染
• 验证水合是否正常工作
• 检查控制台中是否有水合不匹配问题
• 确保仅客户端代码受到 browser 检查的保护

测试模式

Runes 单元测试

import { mount } from 'svelte';
import { tick } from 'svelte';
import { describe, it, expect } from 'vitest';
import Counter from './Counter.svelte';

describe('Counter', () => {
  it('increments count', async () => {
    const { component } = mount(Counter, {
      target: document.body,
      props: { initialCount: 0 }
    });

    const button = document.querySelector('button');
    button?.click();

    await tick();

    expect(button?.textContent).toContain('1');
  });
});

测试 Store 桥接

import { get } from 'svelte/store';
import { tick } from 'svelte';
import { describe, it, expect } from 'vitest';
import { createMyStore } from './myStore';

describe('Store Bridge', () => {
  it('syncs store to rune state', async () => {
    const store = createMyStore();

    store.data.set(['item1', 'item2']);

    await tick();

    expect(get(store.data)).toEqual(['item1', 'item2']);
  });
});

性能注意事项

避免不必要的响应性

// ❌ Over-reactive
let items = $state([1, 2, 3, 4, 5]);
let doubled = $derived(items.map(x => x * 2));
let tripled = $derived(items.map(x => x * 3));
let quadrupled = $derived(items.map(x => x * 4));

// ✅ Compute only what's needed
let items = $state([1, 2, 3, 4, 5]);
let transformedItems = $derived(
  mode === 'double' ? items.map(x => x * 2) :
  mode === 'triple' ? items.map(x => x * 3) :
  items.map(x => x * 4)
);

缓存开销较大的计算

// Traditional derived store for expensive computations
const expensiveComputation = derived(
  [source1, source2],
  ([$s1, $s2]) => {
    // Expensive calculation
    return complexAlgorithm($s1, $s2);
  }
);

// Bridge to rune
let result = $state(null);
$effect(() => {
  const unsub = expensiveComputation.subscribe(v => { result = v; });
  return unsub;
});

故障排除

症状：水合后状态没有更新

原因：在 adapter-static 中于模块作用域使用 runes

修复：使用传统的 writable() store 管理全局状态

症状：在 $derived 中出现 "$ is not defined" 错误

原因：尝试在 runes 模式中使用 $store 语法

修复：使用带 $effect() 订阅的桥接模式

症状：SSG 后出现 "Cannot read property of undefined"

原因：使用带 getter 的 Store 工厂，而非直接导出 store

修复：直接导出 store，不要将它们包装在 getter 中

症状：出现水合不匹配警告

原因：在 SSR 期间渲染了仅客户端状态

修复：使用 browser 检查进行保护，或使用 {#if browser}

决策框架

适用传统 Store 的情况：

• 状态需要在 SSG/SSR 预渲染期间保留
• 状态是全局状态，或需在多个组件间共享
• 状态需要序列化／反序列化
• 使用 adapter-static

适用 Runes 的情况：

• 状态仅限组件内部使用
• 构建响应式 UI 逻辑
• 使用 props 和组件生命周期
• 根据局部状态创建派生计算

适用桥接模式的情况：

• 需要将全局 Store 与组件 Runes 结合
• 希望根据 Store 值进行派生计算
• 构建复杂的响应式链

相关技能

• toolchains-javascript-frameworks-svelte：Svelte 基础模式
• toolchains-typescript-core：TypeScript 集成
• toolchains-ui-styling-tailwind：Svelte 组件样式
• toolchains-javascript-testing-vitest：测试 Svelte 5

参考资料

• Svelte 5 Runes 文档
• SvelteKit adapter-static
• Svelte Stores