From 1279a33259a967b731605046fcbc1dfed9c0a835 Mon Sep 17 00:00:00 2001
From: Oliver Sand <oliver.sand@sda-se.com>
Date: Tue, 6 Apr 2021 15:23:52 +0200
Subject: [PATCH] Handle chunk loading errors

Signed-off-by: Oliver Sand <oliver.sand@sda-se.com>
---
 .changeset/forty-queens-hear.md               |  7 +++
 packages/core-api/src/app/types.ts            |  2 +-
 .../core-api/src/extensions/extensions.tsx    | 56 +++++++++++--------
 packages/core/src/api-wrappers/createApp.tsx  | 34 ++++++++---
 4 files changed, 67 insertions(+), 32 deletions(-)
 create mode 100644 .changeset/forty-queens-hear.md

diff --git a/.changeset/forty-queens-hear.md b/.changeset/forty-queens-hear.md
new file mode 100644
index 0000000000..5e0b35162a
--- /dev/null
+++ b/.changeset/forty-queens-hear.md
@@ -0,0 +1,7 @@
+---
+'@backstage/core': patch
+'@backstage/core-api': patch
+---
+
+Introduce a `load-chunk` step in the `BootErrorPage` to show make chunk loading
+errors visible to the user.
diff --git a/packages/core-api/src/app/types.ts b/packages/core-api/src/app/types.ts
index 5bdf51837d..cf3aaac931 100644
--- a/packages/core-api/src/app/types.ts
+++ b/packages/core-api/src/app/types.ts
@@ -24,7 +24,7 @@ import { AppConfig } from '@backstage/config';
 import { SubRouteRef } from '../routing/types';
 
 export type BootErrorPageProps = {
-  step: 'load-config';
+  step: 'load-config' | 'load-chunk';
   error: Error;
 };
 
diff --git a/packages/core-api/src/extensions/extensions.tsx b/packages/core-api/src/extensions/extensions.tsx
index 9463e437e3..8ff4055e61 100644
--- a/packages/core-api/src/extensions/extensions.tsx
+++ b/packages/core-api/src/extensions/extensions.tsx
@@ -15,9 +15,10 @@
  */
 
 import React, { lazy, Suspense } from 'react';
+import { useApp } from '../app';
+import { BackstagePlugin, Extension } from '../plugin/types';
 import { RouteRef, useRouteRef } from '../routing';
 import { attachComponentData } from './componentData';
-import { Extension, BackstagePlugin } from '../plugin/types';
 
 type ComponentLoader<T> =
   | {
@@ -40,30 +41,41 @@ export function createRoutableExtension<
   return createReactExtension({
     component: {
       lazy: () =>
-        component().then(InnerComponent => {
-          const RoutableExtensionWrapper: any = (props: any) => {
-            // Validate that the routing is wired up correctly in the App.tsx
-            try {
-              useRouteRef(mountPoint);
-            } catch {
-              throw new Error(
-                `Routable extension component with mount point ${mountPoint} was not discovered in the app element tree. ` +
-                  'Routable extension components may not be rendered by other components and must be ' +
-                  'directly available as an element within the App provider component.',
-              );
-            }
-            return <InnerComponent {...props} />;
-          };
+        component().then(
+          InnerComponent => {
+            const RoutableExtensionWrapper: any = (props: any) => {
+              // Validate that the routing is wired up correctly in the App.tsx
+              try {
+                useRouteRef(mountPoint);
+              } catch {
+                throw new Error(
+                  `Routable extension component with mount point ${mountPoint} was not discovered in the app element tree. ` +
+                    'Routable extension components may not be rendered by other components and must be ' +
+                    'directly available as an element within the App provider component.',
+                );
+              }
+              return <InnerComponent {...props} />;
+            };
 
-          const componentName =
-            (InnerComponent as { displayName?: string }).displayName ||
-            InnerComponent.name ||
-            'LazyComponent';
+            const componentName =
+              (InnerComponent as { displayName?: string }).displayName ||
+              InnerComponent.name ||
+              'LazyComponent';
 
-          RoutableExtensionWrapper.displayName = `RoutableExtension(${componentName})`;
+            RoutableExtensionWrapper.displayName = `RoutableExtension(${componentName})`;
 
-          return RoutableExtensionWrapper as T;
-        }),
+            return RoutableExtensionWrapper as T;
+          },
+          error => {
+            const RoutableExtensionWrapper: any = (_: any) => {
+              const app = useApp();
+              const { BootErrorPage } = app.getComponents();
+
+              return <BootErrorPage step="load-chunk" error={error} />;
+            };
+            return RoutableExtensionWrapper;
+          },
+        ),
     },
     data: {
       'core.mountPoint': mountPoint,
diff --git a/packages/core/src/api-wrappers/createApp.tsx b/packages/core/src/api-wrappers/createApp.tsx
index db8d0d0636..b071c2d014 100644
--- a/packages/core/src/api-wrappers/createApp.tsx
+++ b/packages/core/src/api-wrappers/createApp.tsx
@@ -97,16 +97,32 @@ export function createApp(options?: AppOptions) {
     <ErrorPage status="404" statusMessage="PAGE NOT FOUND" />
   );
   const DefaultBootErrorPage = ({ step, error }: BootErrorPageProps) => {
-    let message = '';
-    if (step === 'load-config') {
-      message = `The configuration failed to load, someone should have a look at this error: ${error.message}`;
+    switch (step) {
+      case 'load-config':
+        // TODO: figure out a nicer way to handle routing on the error page, when it can be done.
+        return (
+          <MemoryRouter>
+            <ErrorPage
+              status="501"
+              statusMessage={`The configuration failed to load, someone should have a look at this error: ${error.message}`}
+            />
+          </MemoryRouter>
+        );
+      case 'load-chunk':
+        return (
+          <ErrorPage
+            status="501"
+            statusMessage={`Lazy loaded chunk failed to load, try to reload the page: ${error.message}`}
+          />
+        );
+      default:
+        // TODO: figure out a nicer way to handle routing on the error page, when it can be done.
+        return (
+          <MemoryRouter>
+            <ErrorPage status="501" statusMessage="" />
+          </MemoryRouter>
+        );
     }
-    // TODO: figure out a nicer way to handle routing on the error page, when it can be done.
-    return (
-      <MemoryRouter>
-        <ErrorPage status="501" statusMessage={message} />
-      </MemoryRouter>
-    );
   };
 
   const apis = options?.apis ?? [];