chore: improve backend init error message

Include extension point ID and module ID in backend init error message.

Signed-off-by: Patrick Jungermann <Patrick.Jungermann@gmail.com>

.changeset/gorgeous-bobcats-press.md

@@ -0,0 +1,5 @@
+---
+'@backstage/backend-app-api': patch
+---
+
+Include the extension point ID and the module ID in the backend init error message.

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

@@ -321,7 +321,7 @@ describe('BackendInitializer', () => {
       })(),
     );
     await expect(init.start()).rejects.toThrow(
-      "Extension point registered for plugin 'test-a' may not be used by module for plugin 'test-b'",
+      "Illegal dependency: Module 'mod' for plugin 'test-b' attempted to depend on extension point 'a' for plugin 'test-a'. Extension points can only be used within their plugin's scope.",
     );
   });
 });

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

@@ -55,6 +55,7 @@ export class BackendInitializer {
   async #getInitDeps(
     deps: { [name: string]: ServiceOrExtensionPoint },
     pluginId: string,
+    moduleId?: string,
   ) {
     const result = new Map<string, unknown>();
     const missingRefs = new Set<ServiceOrExtensionPoint>();
@@ -64,7 +65,7 @@ export class BackendInitializer {
       if (ep) {
         if (ep.pluginId !== pluginId) {
           throw new Error(
-            `Extension point registered for plugin '${ep.pluginId}' may not be used by module for plugin '${pluginId}'`,
+            `Illegal dependency: Module '${moduleId}' for plugin '${pluginId}' attempted to depend on extension point '${ref.id}' for plugin '${ep.pluginId}'. Extension points can only be used within their plugin's scope.`,
           );
         }
         result.set(name, ep.impl);
@@ -260,6 +261,7 @@ export class BackendInitializer {
               const moduleDeps = await this.#getInitDeps(
                 moduleInit.init.deps,
                 pluginId,
+                moduleId,
               );
               await moduleInit.init.func(moduleDeps).catch(error => {
                 throw new ForwardedError(

packages/backend-test-utils/src/next/wiring/TestBackend.test.ts

@@ -307,7 +307,7 @@ describe('TestBackend', () => {
         ],
       }),
     ).rejects.toThrow(
-      "Extension point registered for plugin 'testA' may not be used by module for plugin 'testB'",
+      "Illegal dependency: Module 'test' for plugin 'testB' attempted to depend on extension point 'a' for plugin 'testA'. Extension points can only be used within their plugin's scope.",
     );
   });