#Observing Proxy objects in Webstorm debugger

15 messages · Page 1 of 1 (latest)

lilac bluffBOT
#

Hi @plucky dust. I'm kapa.ai, your friendly support bot. I will try to answer your question by searching through the knowledge base. :wave:

#

This is a common issue when working with reactive objects in Nuxt/Vue. What you're experiencing is related to how Nuxt handles promises and reactive objects.

In Nuxt 3, functions like useFetch and other composables that return promises have a special behavior. They return a promise that is also enhanced with reactive properties. This is why you can use them both with and without await:

// Both of these work
const { data } = useFetch('...')
const { data } = await useFetch('...')

As explained in a Stack Overflow answer about this behavior:

If you look at the implementation of useFetch in nuxt3, you will see first that is not an async function. It uses useAsyncData under the hood, again not an async function, which [...] "mixes" a promise with the reactive properties you know (asyncData has the properties data, pending, status, error, ...), so you can either use await (i.e. the promise) or not, and more or less get the same behavior.
Stack Overflow - Why can I access the return value of useFetch without await keyword?

When you're debugging in WebStorm, the debugger might not fully evaluate the Proxy object until it's actually accessed. When you add a console.log(), it forces the evaluation of the Proxy, which is why you suddenly see the value.

This is particularly important to understand when working with composables in Nuxt, as they often return reactive objects wrapped in Proxies. The Vue/Nuxt reactivity system uses these Proxies to track changes to objects.

For debugging these types of objects:

  1. You can use console.log() before your breakpoint to force evaluation
  2. In the debugger, try expanding the Proxy object to see its internal properties
  3. For reactive objects, look for the .value property if it's a ref
#

This behavior is part of how Nuxt handles async operations and reactivity, making it possible to use composables in a more flexible way.

Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:

#

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

plucky dust
#

@lilac bluff what do you mean by expanding the Proxy object in the debugger ?

lilac bluffBOT
#

Let me check the knowledge base for you again. One moment! :books:

#

When I mentioned "expanding the Proxy object in the debugger," I was referring to how you can interact with Proxy objects in WebStorm's debugger interface.

In WebStorm (and other JetBrains IDEs), when you hit a breakpoint and the debugger shows variables in the Variables panel, Proxy objects appear as collapsible tree structures. You can click on the small arrow or plus sign next to the Proxy object to "expand" it and see its internal structure.

When expanded, a Proxy object typically shows:

  1. The [[Target]] - the original object being wrapped
  2. The [[Handler]] - the object containing the traps that intercept operations
  3. Other internal properties

For reactive objects in Nuxt/Vue, expanding the Proxy allows you to see the actual data contained within. For example, if you have a ref created with ref(), you'll need to expand it to see the .value property that contains the actual data.

As mentioned in the Nuxt documentation about debugging:

nuxi dev --inspect

This will start Nuxt in dev mode with the debugger active, allowing you to inspect these objects more effectively Debugging in Nuxt.

WebStorm is also officially supported for Nuxt development, as mentioned in a recent documentation update Github PR #29845, which makes it a good choice for debugging Nuxt applications.

Remember that some Proxy behaviors in Nuxt are specifically designed for reactivity and may behave differently than you might expect when debugging, which is why techniques like console logging before inspection can help force evaluation.

I hope this clarifies what I meant by expanding Proxy objects in the debugger!

Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:

#

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

plucky dust
#

@lilac bluff Hm, since the abc value is "undefined" i cant really expand anything :/

lilac bluffBOT
#

Let me check the knowledge base for you again. One moment! :books:

#

I understand your frustration with debugging Proxy objects in WebStorm. When the value appears as "undefined" in the debugger, you indeed can't expand it.

This is a known issue when working with reactive objects in Nuxt. The problem might be related to how Nuxt's reactivity system works, especially with async operations. When the debugger evaluates the variable at the breakpoint, the Proxy might not have been fully resolved yet.

Here are some alternative debugging approaches you can try:

  1. Enable Nuxt debugging mode by adding debug: true to your nuxt.config.ts file. This will provide more verbose logging that might help identify what's happening with your Proxy objects:
export default defineNuxtConfig({
  debug: true,
  // other config
})

As mentioned in a recent PR, this helps track changes to Nuxt options Github PR #30555.

  1. Try using useAsyncData instead of useFetch if that's what you're using. Some users have reported that useAsyncData works better in production builds while useFetch can cause hydration issues:
// Works prod and dev
const { data } = await useAsyncData(
  'key-name',
  () => $fetch(url)
) 

// May have issues in prod
const { data } = await useFetch(url)

This workaround was mentioned in a GitHub issue about hydration failures Github Issue #31355.

  1. Add a watch statement in your code to see when the value changes:
watch(abc, (newValue) => {
  console.log('abc changed:', newValue)
}, { immediate: true, deep: true })

This approach was suggested in a Stack Overflow post about watching route changes Stack Overflow #77848758.

#
  1. Use the Vue DevTools extension alongside WebStorm's debugger, as it's specifically designed to inspect reactive state.

If you're working with custom components, remember that you need to use defineExpose to make refs accessible to parent components, as mentioned in Stack Overflow #76859379.

Let me know if any of these approaches help with your debugging!

Note: you can ask me a follow up question by @ mentioning me again :speech_balloon:

#

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

plucky dust
#

Sorry, this is not helpful, how do you even debug code like this .... very disappointing :(

plucky dust
#

So, no one ever came across this issue in nuxt/vue ? That's strange .....