docs: add custom useFetch recipe (#27208)

docs/2.guide/0.index.md

@@ -16,4 +16,7 @@ surround: false
   ::card{icon="i-ph-star-duotone" title="Going Further" to="/docs/guide/going-further"}
   Master Nuxt with advanced concepts like experimental features, hooks, modules, and more.
   ::
+  ::card{icon="i-ph-book-open-duotone" title="Recipes" to="/docs/guide/recipes"}
+  Find solutions to common problems and learn how to implement them in your Nuxt project.
+  ::
 ::

docs/2.guide/4.recipes/3.custom-usefetch.md

@@ -0,0 +1,105 @@
+---
+navigation.title: 'Custom useFetch'
+title: Custom useFetch in Nuxt
+description: How to create a custom fetcher for calling your external API in Nuxt 3.
+---
+
+When working with Nuxt, you might be making the frontend and fetching an external API, and you might want to set some default options for fetching from your API.
+
+The [`$fetch`](/docs/api/utils/dollarfetch) utility function (used by the [`useFetch`](/docs/api/composables/use-fetch) composable) is intentionally not globally configurable. This is important so that fetching behavior throughout your application remains consistent, and other integrations (like modules) can rely on the behavior of core utilities like `$fetch`.
+
+However, Nuxt provides a way to create a custom fetcher for your API (or multiple fetchers if you have multiple APIs to call).
+
+## Custom `$fetch`
+
+Let's create a custom `$fetch` instance with a [Nuxt plugin](/docs/guide/directory-structure/plugins).
+
+::note
+`$fetch` is a configured instance of [ofetch](https://github.com/unjs/ofetch) which supports adding the base URL of your Nuxt server as well as direct function calls during SSR (avoiding HTTP roundtrips).
+::
+
+Let's pretend here that:
+- The main API is https://api.nuxt.com
+- We are storing the JWT token in a session with [nuxt-auth-utils](https://github.com/atinux/nuxt-auth-utils)
+- If the API responds with a `401` status code, we redirect the user to the `/login` page
+
+```ts [plugins/api.ts]
+export default defineNuxtPlugin(() => {
+  const { session } = useUserSession()
+
+  const api = $fetch.create({
+    baseURL: 'https://api.nuxt.com',
+    onRequest({ request, options, error }) {
+      if (session.value?.token) {
+        const headers = options.headers ||= {}
+        if (Array.isArray(headers)) {
+          headers.push(['Authorization', `Bearer ${session.value?.token}`])
+        } else if (headers instanceof Headers) {
+          headers.set('Authorization', `Bearer ${session.value?.token}`)
+        } else {
+          headers.Authorization = `Bearer ${session.value?.token}`
+        }
+      }
+    },
+    async onResponseError({ response }) {
+      if (response.status === 401) {
+        await navigateTo('/login')
+      }
+    }
+  })
+
+  // Expose to useNuxtApp().$api
+  return {
+    provide: {
+      api
+    }
+  }
+})
+```
+
+With this Nuxt plugin, `$api` is exposed from `useNuxtApp()` to make API calls directly from the Vue components:
+
+```vue [app.vue]
+<script setup>
+const { $api } = useNuxtApp()
+const { data: modules } = await useAsyncData('modules', () => $api('/modules'))
+</script>
+```
+
+::callout
+Wrapping with [`useAsyncData`](/docs/api/composables/use-async-data) **avoid double data fetching when doing server-side rendering** (server & client on hydration).
+::
+
+## Custom `useFetch`
+
+Now that `$api` has the logic we want, let's create a `useAPI` composable to replace the usage of `useAsyncData` + `$api`:
+
+```ts [composables/useAPI.ts]
+import type { UseFetchOptions } from 'nuxt/app'
+
+export function useAPI<T>(
+  url: string | (() => string),
+  options: Omit<UseFetchOptions<T>, 'default'> & { default: () => T | Ref<T> },
+) {
+  return useFetch(url, {
+    ...options,
+    $fetch: useNuxtApp().$api
+  })
+}
+```
+
+Let's use the new composable and have a nice and clean component:
+
+```vue [app.vue]
+<script setup>
+const { data: modules } = await useAPI('/modules')
+</script>
+```
+
+::callout{icon="i-simple-icons-youtube" color="red" to="https://www.youtube.com/watch?v=jXH8Tr-exhI"}
+Watch a video about custom `$fetch` and Repository Pattern in Nuxt.
+::
+
+::note
+We are currently discussing to find a cleaner way to let you create a custom fetcher, see https://github.com/nuxt/nuxt/issues/14736.
+::