fix(routing): enforce RoutingManager is the last widget

src/lib/InstantSearch.js

@@ -195,6 +195,12 @@ To help you migrate, please refer to the migration guide: https://community.algo
       );
     }
 
+    // The routing manager widget is always added manually at the last position.
+    // By removing it from the last position and adding it back after, we ensure
+    // it keeps this position.
+    // fixes #3148
+    const lastWidget = this.widgets.pop();
+
     widgets.forEach(widget => {
       // Add the widget to the list of widget
       if (widget.render === undefined && widget.init === undefined) {
@@ -204,6 +210,9 @@ To help you migrate, please refer to the migration guide: https://community.algo
       this.widgets.push(widget);
     });
 
+    // Second part of the fix for #3148
+    if (lastWidget) this.widgets.push(lastWidget);
+
     // Init the widget directly if instantsearch has been already started
     if (this.started && Boolean(widgets.length)) {
       this.searchParameters = this.widgets.reduce(enhanceConfiguration({}), {

src/lib/__tests__/InstantSearch-test.js

@@ -260,16 +260,15 @@ describe('InstantSearch lifecycle', () => {
     });
   });
 
-  describe('when we have 5 widgets', () => {
+  describe('when we have 5 widgets (at once)', () => {
     let widgets;
 
     beforeEach(() => {
-      widgets = range(5);
-      widgets = widgets.map((widget, widgetIndex) => ({
+      widgets = range(5).map((widget, widgetIndex) => ({
         init() {},
         getConfiguration: sinon.stub().returns({ values: [widgetIndex] }),
       }));
-      widgets.forEach(search.addWidget, search);
+      search.addWidgets(widgets);
       search.start();
     });