Nuxt•2mo ago

useId() hydration mismatch

I'm experiencing an issue when using useId while creating form field components. I get warnings only on the <label> elements accompanying an input, and the issue is that there is always an extra 0 in the id string, e.g.

- rendered on server: for="v-0-0-0-0-0-0-0-0-0-1-0-0-0-0-0-0-0_9"
  - expected on client: for="v-0-0-0-0-0-0-0-0-0-0-1-0-0-0-0-0-0-0-0_9"

- rendered on server: for="v-0-0-0-0-0-0-0-0-0-1-0-0-0-0-0-0-0_9"
  - expected on client: for="v-0-0-0-0-0-0-0-0-0-0-1-0-0-0-0-0-0-0-0_9"

5 Replies

kapa.ai•2mo ago

Hi @slava. I'm kapa.ai, your friendly support bot. I will try to answer your question by searching through the knowledge base. :wave: ---------------------- You're experiencing a hydration mismatch with useId() in Nuxt, which is a known issue that can occur in specific scenarios. This mismatch happens when the ID generated on the server differs from the one generated on the client during hydration. Why this happens The hydration mismatch occurs because Vue needs to maintain consistency between server and client rendering. When using features like useAsyncData or other async operations, they can affect the component tree structure or execution order, causing the IDs to be generated differently between server and client. Several recent PRs in Nuxt have addressed similar issues: 1. A specific issue was identified where useId would generate different IDs after hydration when useAsyncData was used in a parent component Github Issue #30289 2. The Nuxt team implemented a fix by adding an empty array to the instance.sp within useAsyncData to avoid hydration issues with useId PR #30343 3. Other improvements included using useId instead of build-time hashes for island client components PR #30151 and client-fallback components PR #30314 Solutions To resolve this issue, you can try the following approaches: 1. Update to the latest Nuxt version: Many hydration issues with useId() have been fixed in recent releases. 2. Avoid modifying data during rendering: Ensure you're not modifying props or data during the rendering process, as this can cause hydration mismatches. For example, using methods like shift() on arrays can cause issues as explained in this Stack Overflow post. 3. Create local copies of data: If you need to modify data, create a local copy first:

   const localData = [...props.data]

   const localData = [...props.data]

4. Check async data usage: If you're using useAsyncData in parent components, this might be affecting the ID generation. Try to restructure your components to minimize this effect. 5. Use consistent DOM structures: Ensure your components have the same structure on both server and client to avoid hydration mismatches. The pattern in your error (with many zeros in the ID) suggests that there might be multiple nested components all using useId(), which can make debugging more challenging. Consider simplifying your component structure if possible. Vue 3.4 and Nuxt's implementation of useId() have improved hydration error reporting, making these issues easier to debug than before, as mentioned in this YouTube video. ---------------------- Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: ----------------------

kapa.ai•2mo ago

<@492539613034971146> Kapa.ai is still learning and improving, please let me know how I did by reacting below.

slavaOP•2mo ago

@kapa.ai Can you elaborate on #4? I am retrieving data on the parent page with useAsyncQuery (a wrapper for useAsyncData specifically for Apollo/GraphQL)

const { data } = await useAsyncQuery<ProductQueryResult>(GetProductDocument, {
    slug,
  })

const { data } = await useAsyncQuery<ProductQueryResult>(GetProductDocument, {
    slug,
  })

kapa.ai•2mo ago

Let me check the knowledge base for you again. One moment! :books: ---------------------- I'd be happy to elaborate on how useAsyncData (and by extension useAsyncQuery) can affect useId() and cause hydration mismatches. How useAsyncData/useAsyncQuery affects useId() When you use useAsyncQuery in a parent component, it can affect the component tree structure during server-side rendering versus client-side hydration. This is because: 1. useAsyncData (which powers useAsyncQuery) is designed to fetch data on the server and transfer it to the client via the Nuxt payload, avoiding duplicate requests during hydration Nuxt Docs. 2. A specific issue was identified where using useAsyncData in a parent component causes useId() in child components to generate different IDs after hydration Github Issue #30289. 3. The issue occurs because the component instance state differs between server and client rendering, affecting how Vue's useId() generates sequential IDs. Solutions for your specific case Since you're using useAsyncQuery in your parent component, here are some approaches to resolve the hydration mismatch: 1. Update to the latest Nuxt version: The Nuxt team has implemented fixes for this specific issue in recent versions, including a fix that adds an empty array to the instance.sp within useAsyncData PR #30343. 2. Move ID generation to client-only: If possible, consider using a client-only approach for generating IDs for form elements:

   <script setup>
   const inputId = ref(null)
   
   onMounted(() => {
     // Generate ID only on client
     inputId.value = `input-${Math.random().toString(36).substring(2)}`
   })
   </script>
   
   <template>
     <div>
       <label :for="inputId">Label</label>
       <input :id="inputId" />
     </div>
   </template>

   <script setup>
   const inputId = ref(null)
   
   onMounted(() => {
     // Generate ID only on client
     inputId.value = `input-${Math.random().toString(36).substring(2)}`
   })
   </script>
   
   <template>
     <div>
       <label :for="inputId">Label</label>
       <input :id="inputId" />
     </div>
   </template>

3. Use a consistent manual ID strategy: Instead of relying on useId(), you could create your own ID generation that's deterministic and doesn't depend on component tree structure:

   <script setup>
   const props = defineProps(['fieldName'])
   const inputId = `field-${props.fieldName}`
   </script>

   <script setup>
   const props = defineProps(['fieldName'])
   const inputId = `field-${props.fieldName}`
   </script>

4. Isolate async data fetching: Consider moving your data fetching to a separate component that doesn't contain the form elements using useId(), creating a clearer separation between data fetching and UI rendering. The key insight is that useAsyncData/useAsyncQuery can affect the component instance state between server and client, which in turn affects how useId() generates IDs. By either updating to the latest Nuxt version with fixes or implementing one of the alternative approaches, you should be able to resolve the hydration mismatch. ---------------------- Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: ----------------------

kapa.ai•2mo ago

<@492539613034971146> Kapa.ai is still learning and improving, please let me know how I did by reacting below.

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useId() hydration mismatch

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