nuxt/4/shallow-function-reactivity

This codemod transforms the data object returned from useAsyncData, useFetch, useLazyAsyncData and useLazyFetch into a shallowRef

When new data is fetched, anything depending on data will still be reactive because the entire object is replaced. But if your code changes a property within that data structure, this will not trigger any reactivity in your app.

This brings a significant performance improvement for deeply nested objects and arrays because Vue does not need to watch every single property/array for modification. In most cases, data should also be immutable.

Before

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const { data } = useFetch("/api/test");

This can apply to all useAsyncData, useFetch, useLazyAsyncData and useLazyFetch.

After

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const { data } = useFetch("/api/test", { deep: true });

Additional Feature

This codemod ensures that any unique key of your data is always resolvable to the same data. For example, if you are using useAsyncData to fetch data related to a particular page, it should be changed to a key that uniquely matches that data. (useFetch should do this automatically for you.)

Example

Code before transformation:

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const route = useRoute();
const { data } = await useAsyncData(async () => {
  return await $fetch(`/api/my-page/${route.params.slug}`);
});

Code after transformation:

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const route = useRoute();
const { data } = await useAsyncData(route.params.slug, async () => {
  return await $fetch(`/api/my-page/${route.params.slug}`), { deep: true };
});