backend-app-api: better error message for missing service deps

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

.changeset/gorgeous-scissors-wave.md

@@ -0,0 +1,5 @@
+---
+'@backstage/backend-app-api': patch
+---
+
+Updated the error message for missing service dependencies to include the plugin and module IDs.

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

@@ -577,6 +577,56 @@ describe('BackendInitializer', () => {
     );
   });
 
+  it('should reject plugins with missing dependencies', async () => {
+    const init = new BackendInitializer(baseFactories);
+    const ref = createServiceRef<string>({ id: 'a' });
+    init.add(
+      createBackendPlugin({
+        pluginId: 'test',
+        register(reg) {
+          reg.registerInit({
+            deps: { ref },
+            async init() {},
+          });
+        },
+      }),
+    );
+    await expect(init.start()).rejects.toThrow(
+      "Service or extension point dependencies of plugin 'test' are missing for the following ref(s): serviceRef{a}",
+    );
+  });
+
+  it('should reject modules with missing dependencies', async () => {
+    const init = new BackendInitializer(baseFactories);
+    const ref = createServiceRef<string>({ id: 'a' });
+    init.add(
+      createBackendPlugin({
+        pluginId: 'test',
+        register(reg) {
+          reg.registerInit({
+            deps: {},
+            async init() {},
+          });
+        },
+      }),
+    );
+    init.add(
+      createBackendModule({
+        pluginId: 'test',
+        moduleId: 'test-mod',
+        register(reg) {
+          reg.registerInit({
+            deps: { ref },
+            async init() {},
+          });
+        },
+      }),
+    );
+    await expect(init.start()).rejects.toThrow(
+      "Service or extension point dependencies of module 'test-mod' for plugin 'test' are missing for the following ref(s): serviceRef{a}",
+    );
+  });
+
   it('should properly load double-default CJS modules', async () => {
     expect.assertions(3);
 

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

@@ -93,8 +93,11 @@ export class BackendInitializer {
 
     if (missingRefs.size > 0) {
       const missing = Array.from(missingRefs).join(', ');
+      const target = moduleId
+        ? `module '${moduleId}' for plugin '${pluginId}'`
+        : `plugin '${pluginId}'`;
       throw new Error(
-        `No extension point or service available for the following ref(s): ${missing}`,
+        `Service or extension point dependencies of ${target} are missing for the following ref(s): ${missing}`,
       );
     }