🐛 RBAC: Incompatible with Backstage 1.47 (FetchUrlReader constructor is now private)

[wingleung]

Workspace

rbac

📜 Description

The RBAC backend plugin fails to start with Backstage 1.47.x due to a breaking change in @backstage/backend-defaults@0.15.0 where the FetchUrlReader constructor was made private.

👍 Expected behavior

The RBAC backend plugin should start successfully with Backstage 1.47.x.

👎 Actual Behavior with Screenshots

The backend fails to start with the following error:

TypeError: Cannot read properties of undefined (reading 'predicate')                                                                                                                                             
  at new FetchUrlReader (.../node_modules/@backstage-community/plugin-rbac-backend/node_modules/@backstage/backend-defaults/src/entrypoints/urlReader/lib/FetchUrlReader.ts:135:31)                            
  at permissionFactory (.../node_modules/@backstage-community/plugin-rbac-backend/src/service/plugin-endpoints.ts:125:23)  

👟 Reproduction steps

1. Upgrade Backstage to 1.47.x using yarn backstage-cli versions:bump
2. Ensure @backstage-community/plugin-rbac-backend@^7.6.1 is installed
3. Run yarn start or yarn dev
4. Backend fails during RBAC plugin initialization

📃 Provide the context for the Bug.

In @backstage/backend-defaults@0.15.0, the FetchUrlReader constructor was made private. The changelog states:

27f9061: BREAKING: The constructor for FetchUrlReader is now private. If you have to construct an instance of it, please use FetchUrlReader.fromConfig instead.

The RBAC plugin still uses the old pattern in plugin-endpoints.ts:

private static permissionFactory: ReaderFactory = () => {
  return [{ reader: new FetchUrlReader(), predicate: (_url: URL) => true }];
};

Suggested fix: Update to use FetchUrlReader.fromConfig(config) instead of new FetchUrlReader().

Versions

• Backstage: 1.47.2
• @backstage-community/plugin-rbac-backend: 7.6.1
• @backstage/backend-defaults: 0.15.1

Workaround

Downgrade to Backstage 1.46.x which uses @backstage/backend-defaults@0.14.x.

👀 Have you spent some time to check if this bug has been raised before?

• I checked and didn't find similar issue

🏢 Have you read the Code of Conduct?

• I have read the Code of Conduct

Are you willing to submit PR?

None