From d8c8f17be80a3042e06dda4352d0d924f55d7b9a Mon Sep 17 00:00:00 2001
From: Patrik Oldsberg <poldsberg@gmail.com>
Date: Wed, 9 Jun 2021 22:27:42 +0200
Subject: [PATCH] core-plugin-api: allow unknown plugin outputs for backwards
 compatibility

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>
---
 packages/core-app-api/src/app/createApp.tsx |  3 ++-
 packages/core-app-api/src/app/types.ts      | 18 +++++++++++++++++-
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/packages/core-app-api/src/app/createApp.tsx b/packages/core-app-api/src/app/createApp.tsx
index b93df63ff0..1670978791 100644
--- a/packages/core-app-api/src/app/createApp.tsx
+++ b/packages/core-app-api/src/app/createApp.tsx
@@ -35,6 +35,7 @@ import {
   BootErrorPageProps,
   ErrorBoundaryFallbackProps,
 } from './types';
+import { BackstagePlugin } from '@backstage/core-plugin-api';
 
 /**
  * The default config loader, which expects that config is available at compile-time
@@ -171,7 +172,7 @@ export function createApp(options?: AppOptions) {
   return new PrivateAppImpl({
     apis,
     icons,
-    plugins,
+    plugins: plugins as BackstagePlugin<any, any>[],
     components,
     themes,
     configLoader,
diff --git a/packages/core-app-api/src/app/types.ts b/packages/core-app-api/src/app/types.ts
index 02b62aef16..cf5811beae 100644
--- a/packages/core-app-api/src/app/types.ts
+++ b/packages/core-app-api/src/app/types.ts
@@ -24,6 +24,7 @@ import {
   RouteRef,
   SubRouteRef,
   ExternalRouteRef,
+  PluginOutput,
 } from '@backstage/core-plugin-api';
 import { AppConfig } from '@backstage/config';
 import { AppIcons } from './icons';
@@ -131,6 +132,21 @@ export type AppRouteBinder = <
   >,
 ) => void;
 
+// Output from newer or older plugin API versions that might not be supported by
+// this version of the app API, but we don't want to break at the type checking level.
+// We only use this more permissive type for the `createApp` options, as we otherwise
+// want to stick to using the type for the outputs that we know about in this version
+// of the app api.
+type UnknownPluginOutput = {
+  type: string;
+};
+export type BackstagePluginWithAnyOutput = Omit<
+  BackstagePlugin<any, any>,
+  'output'
+> & {
+  output(): (PluginOutput | UnknownPluginOutput)[];
+};
+
 export type AppOptions = {
   /**
    * A collection of ApiFactories to register in the application to either
@@ -146,7 +162,7 @@ export type AppOptions = {
   /**
    * A list of all plugins to include in the app.
    */
-  plugins?: BackstagePlugin<any, any>[];
+  plugins?: BackstagePluginWithAnyOutput[];
 
   /**
    * Supply components to the app to override the default ones.