backend-app-api: immediately log plugin startup errors

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

.changeset/grumpy-crews-sneeze.md

@@ -0,0 +1,5 @@
+---
+'@backstage/backend-app-api': patch
+---
+
+The log message written when plugins fail to initialize now includes the error that caused the plugin startup to fail.

packages/backend-app-api/src/wiring/BackendInitializer.ts

@@ -34,7 +34,7 @@ import type {
 } from '../../../backend-plugin-api/src/wiring/types';
 // eslint-disable-next-line @backstage/no-relative-monorepo-imports
 import type { InternalServiceFactory } from '../../../backend-plugin-api/src/services/system/types';
-import { ForwardedError, ConflictError } from '@backstage/errors';
+import { ForwardedError, ConflictError, assertError } from '@backstage/errors';
 import {
   instanceMetadataServiceRef,
   featureDiscoveryServiceRef,
@@ -405,8 +405,9 @@ export class BackendInitializer {
           // Once the plugin and all modules have been initialized, we can signal that the plugin has stared up successfully
           const lifecycleService = await this.#getPluginLifecycleImpl(pluginId);
           await lifecycleService.startup();
-        } catch (error) {
-          initLogger.onPluginFailed(pluginId);
+        } catch (error: unknown) {
+          assertError(error);
+          initLogger.onPluginFailed(pluginId, error);
           throw error;
         }
       }),

packages/backend-app-api/src/wiring/createInitializationLogger.ts

@@ -27,7 +27,7 @@ export function createInitializationLogger(
   rootLogger?: RootLoggerService,
 ): {
   onPluginStarted(pluginId: string): void;
-  onPluginFailed(pluginId: string): void;
+  onPluginFailed(pluginId: string, error: Error): void;
   onAllStarted(): void;
 } {
   const logger = rootLogger?.child({ type: 'initialization' });
@@ -68,14 +68,15 @@ export function createInitializationLogger(
       starting.delete(pluginId);
       started.add(pluginId);
     },
-    onPluginFailed(pluginId: string) {
+    onPluginFailed(pluginId: string, error: Error) {
       starting.delete(pluginId);
       const status =
         starting.size > 0
           ? `, waiting for ${starting.size} other plugins to finish before shutting down the process`
           : '';
       logger?.error(
-        `Plugin '${pluginId}' threw an error during startup${status}`,
+        `Plugin '${pluginId}' threw an error during startup${status}.`,
+        error,
       );
     },
     onAllStarted() {