fix(nuxt3): forward $nuxt on the instance by default (#1112)

* fix(nuxt3): forward $nuxt on the instance by default

This is similar to how we forward $router and $store, but in this case it needs to happen before the beforeCreate of nuxt happens

* conditionnel présent

src/util/__tests__/createServerRootMixin.test.js

@@ -660,6 +660,60 @@ Array [
         await renderToString(wrapper);
       });
 
+      it('forwards nuxt', async () => {
+        const searchClient = createFakeClient();
+
+        let nuxt = 0;
+        // every time the function gets called, we get a different "nuxt"
+        // this can be used to assert both "nuxt" objects are equal
+        const getNuxtCounter = () => ++nuxt;
+
+        // there are two renders of App, each with an assertion
+        expect.assertions(2);
+
+        const App = {
+          mixins: [
+            {
+              beforeCreate() {
+                this.$nuxt = getNuxtCounter();
+              },
+            },
+            forceIsServerMixin,
+            createServerRootMixin({
+              searchClient,
+              indexName: 'hello',
+            }),
+          ],
+          data() {
+            expect(this.$nuxt).toEqual(1);
+            return {};
+          },
+          render: renderCompat(h =>
+            h(InstantSearchSsr, {}, [
+              h(Configure, {
+                attrs: {
+                  hitsPerPage: 100,
+                },
+              }),
+              h(SearchBox),
+            ])
+          ),
+          serverPrefetch() {
+            return this.instantsearch.findResultsState({
+              component: this,
+              renderToString,
+            });
+          },
+        };
+
+        const wrapper = createSSRApp({
+          mixins: [forceIsServerMixin],
+          render: renderCompat(h => h(App)),
+        });
+
+        await renderToString(wrapper);
+      });
+
       it('searches only once', async () => {
         const searchClient = createFakeClient();
         const app = {

src/util/createServerRootMixin.js

@@ -41,7 +41,7 @@ function defaultCloneComponent(componentInstance, { mixins = [] } = {}) {
 
   if (isVue3) {
     const appOptions = Object.assign({}, componentInstance.$options, options);
-    appOptions.mixins = [...appOptions.mixins, ...mixins];
+    appOptions.mixins = [...mixins, ...appOptions.mixins];
     app = createSSRApp(appOptions);
     if (componentInstance.$router) {
       app.use(componentInstance.$router);
@@ -104,6 +104,13 @@ function augmentInstantSearch(instantSearchOptions, cloneComponent) {
         app = cloneComponent(component, {
           mixins: [
             {
+              beforeCreate() {
+                if (component.$nuxt) {
+                  // In case of Nuxt (3), we ensure the context is shared between
+                  // the real and cloned component
+                  this.$nuxt = component.$nuxt;
+                }
+              },
               created() {
                 instance = this.instantsearch;