nuxt · danielroe · Mar 6, 2024 · Jun 22, 2023 · Jun 22, 2023 · Jun 22, 2023
@@ -0,0 +1,81 @@
+---
+title: "usePreviewMode"
+description: "Use usePreviewMode to check and control preview mode in Nuxt"
+---
+
+# `usePreviewMode`
+
+You can use the built-in `usePreviewMode` composable to access and control preview state in Nuxt. If the composable detects preview mode it will automatically force any updates necessary for [`useAsyncData`](/docs/api/composables/use-async-data) and [`useFetch`](/docs/api/composables/use-fetch) to rerender preview content.
+
+```js
+const { enabled, state } = usePreviewMode()
+```
+
+## Options
+
+### Custom `enable` check
+
+You can specify a custom way to enable preview mode. By default the `usePreviewMode` composable will enable preview mode if there is a `preview` param in url that is equal to `true` (for example, `http://localhost:3000?preview=true`). You can wrap the `usePreviewMode` into custom composable, to keep options consistent across usages and prevent any errors.
+
+```js
+export function useMyPreviewMode () {
+  return usePreviewMode({
+    shouldEnable: () => {
+      return !!route.query.customPreview
+    }
+  });
+}```
+
+### Modify default state
+
+`usePreviewMode` will try to store the value of a `token` param from url in state. You can modify this state and it will be available for all [`usePreviewMode`](/docs/api/composables/use-preview-mode) calls.
+
+```js
+const data1 = ref('data1')
+
+const { enabled, state } = usePreviewMode({
+  getState: (currentState) => {
+    return { data1, data2: 'data2' }
+  }
+})
+```
+
+::alert{icon=👉}
+The `getState` function will append returned values to current state, so be careful not to accidentally overwrite important state.
+::
+
+## Example
+
+```vue [pages/some-page.vue]
+<script setup>
+const route = useRoute()
+
+const { enabled, state } = usePreviewMode({
+  shouldEnable: () => {
+    return route.query.customPreview === 'true'
+  },
+})
+
+const { data } = await useFetch('/api/preview', {
+  query: {
+    apiKey: state.token
+  }
+})
+</script>
+
+<template>
+  <div>
+    Some base content
+
+    <p v-if="enabled">
+      Only preview content: {{ state.token }}
+
+      <br>
+
+      <button @click="enabled = false">
+        disable preview mode
+      </button>
+    </p>
+  </div>
+</template>
+```
@@ -35,4 +35,5 @@ export type { NuxtAppManifest, NuxtAppManifestMeta } from './manifest'
 export type { ReloadNuxtAppOptions } from './chunk'
 export { reloadNuxtApp } from './chunk'
 export { useRequestURL } from './url'
+export { usePreviewMode } from './preview'
 export { useId } from './id'
@@ -0,0 +1,91 @@
+import { toRef, watch } from 'vue'
+
+import { useState } from './state'
+import { refreshNuxtData } from './asyncData'
+import { useRoute, useRouter } from './router'
+
+interface Preview {
+  enabled: boolean
+  state: Record<any, unknown>
+  _initialized?: boolean
+}
+
+interface PreviewModeOptions<S> {
+  shouldEnable?: (state: Preview['state']) => boolean,
+  getState?: (state: Preview['state']) => S,
+}
+
+type EnteredState = Record<any, unknown> | null | undefined | void
+
+let unregisterRefreshHook: (() => any) | undefined
+
+/** @since 3.11.0 */
+export function usePreviewMode<S extends EnteredState> (options: PreviewModeOptions<S> = {}) {
+  const preview = useState<Preview>('_preview-state', () => ({
+    enabled: false,
+    state: {}
+  }))
+
+  if (preview.value._initialized) {
+    return {
+      enabled: toRef(preview.value, 'enabled'),
+      state: preview.value.state as S extends void ? Preview['state'] : (NonNullable<S> & Preview['state']),
+    }
+  }
+
+  if (import.meta.client) {
+    preview.value._initialized = true
+  }
+
+  if (!preview.value.enabled) {
+    const shouldEnable = options.shouldEnable ?? defaultShouldEnable
+    const result = shouldEnable(preview.value.state)
+
+    if (typeof result === 'boolean') { preview.value.enabled = result }
+  }
+
+  watch(() => preview.value.enabled, (value) => {
+    if (value) {
+      const getState = options.getState ?? getDefaultState
+      const newState = getState(preview.value.state)
+
+      if (newState !== preview.value.state) {
+        Object.assign(preview.value.state, newState)
+      }
+
+      if (import.meta.client && !unregisterRefreshHook) {
+        refreshNuxtData()
+
+        unregisterRefreshHook = useRouter().afterEach((() => refreshNuxtData()))
+      }
+    } else if (unregisterRefreshHook) {
+      unregisterRefreshHook()
+
+      unregisterRefreshHook = undefined
+    }
+  }, { immediate: true, flush: 'sync' })
+
+  return {
+    enabled: toRef(preview.value, 'enabled'),
+    state: preview.value.state as S extends void ? Preview['state'] : (NonNullable<S> & Preview['state']),
+  }
+}
+
+function defaultShouldEnable () {
+  const route = useRoute()
+  const previewQueryName = 'preview'
+
+  return route.query[previewQueryName] === 'true'
+}
+
+function getDefaultState (state: Preview['state']) {
+  if (state.token !== undefined) {
+    return state
+  }
+
+  const route = useRoute()
+
+  state.token = Array.isArray(route.query.token) ? route.query.token[0] : route.query.token
+
+  return state
+}
@@ -101,6 +101,10 @@ const granularAppPresets: InlinePreset[] = [
     imports: ['useRequestURL'],
     from: '#app/composables/url'
   },
+  {
+    imports: ['usePreviewMode'],
+    from: '#app/composables/preview'
+  },
   {
     imports: ['useId'],
     from: '#app/composables/id'

@@ -568,6 +568,61 @@ describe('nuxt composables', () => {
     expect(text).toContain('foobar')
     await page.close()
   })
+
+  it('respects preview mode with a token', async () => {
+    const token = 'hehe'
+    const page = await createPage(`/preview?preview=true&token=${token}`)
+
+    const hasRerunFetchOnClient = await new Promise<boolean>((resolve) => {
+      page.on('console', (message) => {
+        setTimeout(() => resolve(false), 4000)
+
+        if (message.text() === 'true') { resolve(true) }
+      })
+    })
+
+    expect(hasRerunFetchOnClient).toBe(true)
+
+    expect(await page.locator('#fetched-on-client').textContent()).toContain('fetched on client')
+    expect(await page.locator('#preview-mode').textContent()).toContain('preview mode enabled')
+
+    await page.click('#use-fetch-check')
+    await page.waitForFunction(() => window.useNuxtApp?.()._route.fullPath.includes('/preview/with-use-fetch'))
+
+    expect(await page.locator('#token-check').textContent()).toContain(token)
+    expect(await page.locator('#correct-api-key-check').textContent()).toContain('true')
+    await page.close()
+  })
+
+  it('respects preview mode with custom state', async () => {
+    const { page } = await renderPage('/preview/with-custom-state?preview=true')
+
+    expect(await page.locator('#data1').textContent()).toContain('data1 updated')
+    expect(await page.locator('#data2').textContent()).toContain('data2')
+
+    await page.click('#toggle-preview') // manually turns off preview mode
+    await page.click('#with-use-fetch')
+    await page.waitForFunction(() => window.useNuxtApp?.()._route.fullPath.includes('/preview/with-use-fetch'))
+
+    expect(await page.locator('#enabled').textContent()).toContain('false')
+    expect(await page.locator('#token-check').textContent()).toEqual('')
+    expect(await page.locator('#correct-api-key-check').textContent()).toContain('false')
+    await page.close()
+  })
+
+  it('respects preview mode with custom enable', async () => {
+    const { page } = await renderPage('/preview/with-custom-enable?preview=true')
+
+    expect(await page.locator('#enabled').textContent()).toContain('false')
+    await page.close()
+  })
+
+  it('respects preview mode with custom enable and customPreview', async () => {
+    const { page } = await renderPage('/preview/with-custom-enable?customPreview=true')
+
+    expect(await page.locator('#enabled').textContent()).toContain('true')
+    await page.close()
+  })
 })
 
 describe('rich payloads', () => {

@@ -0,0 +1,38 @@
+<script setup>
+const { enabled: isPreview } = usePreviewMode()
+
+const { data } = await useAsyncData(async () => {
+  await new Promise(resolve => setTimeout(resolve, 200))
+
+  const fetchedOnClient = process.client
+
+  console.log(fetchedOnClient)
+
+  return { fetchedOnClient }
+})
+</script>
+
+<template>
+  <div>
+    <NuxtLink
+      id="use-fetch-check"
+      href="/preview/with-use-fetch"
+    >
+      check useFetch
+    </NuxtLink>
+
+    <p
+      v-if="data && data.fetchedOnClient"
+      id="fetched-on-client"
+    >
+      fetched on client
+    </p>
+
+    <p
+      v-if="isPreview"
+      id="preview-mode"
+    >
+      preview mode enabled
+    </p>
+  </div>
+</template>
@@ -0,0 +1,17 @@
+<script setup>
+const route = useRoute()
+
+const { enabled } = usePreviewMode({
+  shouldEnable: () => {
+    return !!route.query.customPreview
+  }
+})
+</script>
+
+<template>
+  <div>
+    <p id="enabled">
+      {{ enabled }}
+    </p>
+  </div>
+</template>
@@ -0,0 +1,39 @@
+<script setup>
+const data1 = ref('data1')
+
+const { enabled, state } = usePreviewMode({
+  getState: () => {
+    return { data1, data2: 'data2' }
+  }
+})
+
+onMounted(() => {
+  data1.value = 'data1 updated'
+})
+</script>
+
+<template>
+  <div>
+    <NuxtLink
+      id="with-use-fetch"
+      to="/preview/with-use-fetch"
+    >
+      fetch check
+    </NuxtLink>
+
+    <p id="data1">
+      {{ state.data1 }}
+    </p>
+
+    <p id="data2">
+      {{ state.data2 }}
+    </p>
+
+    <button
+      id="toggle-preview"
+      @click="enabled = !enabled"
+    >
+      toggle preview mode
+    </button>
+  </div>
+</template>
@@ -0,0 +1,25 @@
+<script setup>
+const { enabled, state } = usePreviewMode()
+
+const { data } = await useFetch('/api/preview', {
+  query: {
+    apiKey: state.token || undefined
+  }
+})
+</script>
+
+<template>
+  <div>
+    <p id="enabled">
+      {{ enabled }}
+    </p>
+
+    <p id="token-check">
+      {{ state.token }}
+    </p>
+
+    <p id="correct-api-key-check">
+      {{ data && data.hehe }}
+    </p>
+  </div>
+</template>
@@ -0,0 +1,8 @@
+const apiKeyName = 'apiKey'
+const apiKey = 'hehe'
+
+export default defineEventHandler((event) => {
+  return {
+    hehe: getQuery(event)[apiKeyName] === apiKey
+  }
+})
@@ -128,7 +128,8 @@ describe('composables', () => {
       'useLazyAsyncData',
       'useRouter',
       'useSeoMeta',
-      'useServerSeoMeta'
+      'useServerSeoMeta',
+      'usePreviewMode'
     ]
     expect(Object.keys(composables).sort()).toEqual([...new Set([...testedComposables, ...skippedComposables])].sort())
   })