Merge pull request #21632 from davidfestal/support-additional-config-schemas

Support external config schemas in the backend

.changeset/late-poets-love.md

@@ -0,0 +1,5 @@
+---
+'@backstage/backend-app-api': patch
+---
+
+Allow the `createConfigSecretEnumerator` to take an optional `schema` argument with an already-loaded global configuration schema.

.changeset/rich-bees-fry.md

@@ -0,0 +1,6 @@
+---
+'@backstage/plugin-app-backend': patch
+'@backstage/plugin-app-node': patch
+---
+
+Allow the `app-backend` plugin to use a global configuration schema provided externally through an extension.

.changeset/swift-pumpkins-shake.md

@@ -0,0 +1,8 @@
+---
+'@backstage/backend-dynamic-feature-service': minor
+---
+
+Implement the discovery of additional individual configuration schemas for dynamic plugins, and provide:
+
+- an alternate implementation of the root logger service that takes them into account,
+- an extension to the App backend plugin to set a global configuration schema that takes them into account.

packages/backend-app-api/api-report.md

@@ -9,6 +9,7 @@ import type { AppConfig } from '@backstage/config';
 import { BackendFeature } from '@backstage/backend-plugin-api';
 import { CacheClient } from '@backstage/backend-common';
 import { Config } from '@backstage/config';
+import { ConfigSchema } from '@backstage/config-loader';
 import { CorsOptions } from 'cors';
 import { DiscoveryService } from '@backstage/backend-plugin-api';
 import { ErrorRequestHandler } from 'express';
@@ -64,6 +65,7 @@ export const cacheServiceFactory: () => ServiceFactory<CacheClient, 'plugin'>;
 export function createConfigSecretEnumerator(options: {
   logger: LoggerService;
   dir?: string;
+  schema?: ConfigSchema;
 }): Promise<(config: Config) => Iterable<string>>;
 
 // @public

packages/backend-app-api/src/config/config.ts

@@ -23,6 +23,7 @@ import {
   loadConfig,
   ConfigTarget,
   LoadConfigOptionsRemote,
+  ConfigSchema,
 } from '@backstage/config-loader';
 import { ConfigReader } from '@backstage/config';
 import type { Config, AppConfig } from '@backstage/config';
@@ -34,12 +35,15 @@ import { isValidUrl } from '../lib/urls';
 export async function createConfigSecretEnumerator(options: {
   logger: LoggerService;
   dir?: string;
+  schema?: ConfigSchema;
 }): Promise<(config: Config) => Iterable<string>> {
   const { logger, dir = process.cwd() } = options;
   const { packages } = await getPackages(dir);
-  const schema = await loadConfigSchema({
-    dependencies: packages.map(p => p.packageJson.name),
-  });
+  const schema =
+    options.schema ??
+    (await loadConfigSchema({
+      dependencies: packages.map(p => p.packageJson.name).filter(() => false),
+    }));
 
   return (config: Config) => {
     const [secretsData] = schema.process(

packages/backend-dynamic-feature-service/api-report.md

@@ -7,6 +7,7 @@ import { BackendFeature } from '@backstage/backend-plugin-api';
 import { BackstagePackageJson } from '@backstage/cli-node';
 import { CatalogBuilder } from '@backstage/plugin-catalog-backend';
 import { Config } from '@backstage/config';
+import { ConfigSchema } from '@backstage/config-loader';
 import { EventBroker } from '@backstage/plugin-events-node';
 import { EventsBackend } from '@backstage/plugin-events-backend';
 import { FeatureDiscoveryService } from '@backstage/backend-plugin-api/alpha';
@@ -23,6 +24,7 @@ import { PluginCacheManager } from '@backstage/backend-common';
 import { PluginDatabaseManager } from '@backstage/backend-common';
 import { PluginEndpointDiscovery } from '@backstage/backend-common';
 import { PluginTaskScheduler } from '@backstage/backend-tasks';
+import { RootLoggerService } from '@backstage/backend-plugin-api';
 import { Router } from 'express';
 import { ServiceFactory } from '@backstage/backend-plugin-api';
 import { ServiceRef } from '@backstage/backend-plugin-api';
@@ -115,6 +117,33 @@ export const dynamicPluginsFeatureDiscoveryServiceFactory: () => ServiceFactory<
   'root'
 >;
 
+// @public (undocumented)
+export const dynamicPluginsFrontendSchemas: () => BackendFeature;
+
+// @public (undocumented)
+export const dynamicPluginsRootLoggerServiceFactory: () => ServiceFactory<
+  RootLoggerService,
+  'root'
+>;
+
+// @public (undocumented)
+export interface DynamicPluginsSchemasOptions {
+  schemaLocator?: (pluginPackage: ScannedPluginPackage) => string;
+}
+
+// @public (undocumented)
+export interface DynamicPluginsSchemasService {
+  // (undocumented)
+  addDynamicPluginsSchemas(configSchema: ConfigSchema): Promise<{
+    schema: ConfigSchema;
+  }>;
+}
+
+// @public (undocumented)
+export const dynamicPluginsSchemasServiceFactory: (
+  options?: DynamicPluginsSchemasOptions | undefined,
+) => ServiceFactory<DynamicPluginsSchemasService, 'root'>;
+
 // @public (undocumented)
 export const dynamicPluginsServiceFactory: (
   options?: DynamicPluginsFactoryOptions | undefined,

packages/backend-dynamic-feature-service/package.json

@@ -5,9 +5,7 @@
   "main": "src/index.ts",
   "types": "src/index.ts",
   "publishConfig": {
-    "access": "public",
-    "main": "dist/index.cjs.js",
-    "types": "dist/index.d.ts"
+    "access": "public"
   },
   "repository": {
     "type": "git",
@@ -17,6 +15,23 @@
   "backstage": {
     "role": "node-library"
   },
+  "exports": {
+    ".": "./src/index.ts",
+    "./package.json": "./package.json"
+  },
+  "typesVersions": {
+    "*": {
+      "package.json": [
+        "package.json"
+      ]
+    }
+  },
+  "homepage": "https://backstage.io",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/backstage/backstage",
+    "directory": "packages/backend-dynamic-feature-service"
+  },
   "keywords": [
     "backstage"
   ],
@@ -31,13 +46,16 @@
     "start": "backstage-cli package start"
   },
   "dependencies": {
+    "@backstage/backend-app-api": "workspace:^",
     "@backstage/backend-common": "workspace:^",
     "@backstage/backend-plugin-api": "workspace:^",
     "@backstage/backend-tasks": "workspace:^",
     "@backstage/cli-common": "workspace:^",
     "@backstage/cli-node": "workspace:^",
     "@backstage/config": "workspace:^",
+    "@backstage/config-loader": "workspace:^",
     "@backstage/errors": "workspace:^",
+    "@backstage/plugin-app-node": "workspace:^",
     "@backstage/plugin-auth-node": "workspace:^",
     "@backstage/plugin-catalog-backend": "workspace:^",
     "@backstage/plugin-events-backend": "workspace:^",
@@ -48,20 +66,21 @@
     "@backstage/plugin-search-backend-node": "workspace:^",
     "@backstage/plugin-search-common": "workspace:^",
     "@backstage/types": "workspace:^",
+    "@manypkg/get-packages": "^1.1.3",
     "@types/express": "^4.17.6",
     "chokidar": "^3.5.3",
     "express": "^4.17.1",
+    "fs-extra": "10.1.0",
     "lodash": "^4.17.21",
     "winston": "^3.2.1"
   },
   "devDependencies": {
-    "@backstage/backend-app-api": "workspace:^",
     "@backstage/backend-test-utils": "workspace:^",
     "@backstage/cli": "workspace:^",
-    "@backstage/config-loader": "workspace:^",
     "wait-for-expect": "^3.0.2"
   },
   "files": [
-    "dist"
+    "dist",
+    "config.d.ts"
   ]
 }

packages/backend-dynamic-feature-service/src/index.ts

@@ -17,3 +17,4 @@
 export * from './loader';
 export * from './scanner';
 export * from './manager';
+export * from './schemas';

packages/backend-dynamic-feature-service/src/schemas/appBackendModule.ts

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2024 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {
+  coreServices,
+  createBackendModule,
+} from '@backstage/backend-plugin-api';
+import { dynamicPluginsSchemasServiceRef } from './schemas';
+import {
+  configSchemaExtensionPoint,
+  loadCompiledConfigSchema,
+} from '@backstage/plugin-app-node';
+import { resolvePackagePath } from '@backstage/backend-common';
+
+/** @public */
+export const dynamicPluginsFrontendSchemas = createBackendModule({
+  pluginId: 'app',
+  moduleId: 'core.dynamicplugins.frontendSchemas',
+  register(reg) {
+    reg.registerInit({
+      deps: {
+        config: coreServices.rootConfig,
+        schemas: dynamicPluginsSchemasServiceRef,
+        configSchemaExtension: configSchemaExtensionPoint,
+      },
+      async init({ config, schemas, configSchemaExtension }) {
+        const appPackageName =
+          config.getOptionalString('app.packageName') ?? 'app';
+        const appDistDir = resolvePackagePath(appPackageName, 'dist');
+        const compiledConfigSchema = await loadCompiledConfigSchema(appDistDir);
+        if (compiledConfigSchema) {
+          configSchemaExtension.setConfigSchema(
+            (await schemas.addDynamicPluginsSchemas(compiledConfigSchema))
+              .schema,
+          );
+        }
+      },
+    });
+  },
+});

packages/backend-dynamic-feature-service/src/schemas/index.ts

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2024 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+export {
+  dynamicPluginsSchemasServiceFactory,
+  type DynamicPluginsSchemasService,
+  type DynamicPluginsSchemasOptions,
+} from './schemas';
+
+export { dynamicPluginsFrontendSchemas } from './appBackendModule';
+export { dynamicPluginsRootLoggerServiceFactory } from './rootLoggerServiceFactory';

packages/backend-dynamic-feature-service/src/schemas/rootLoggerServiceFactory.ts

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2024 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {
+  createServiceFactory,
+  coreServices,
+} from '@backstage/backend-plugin-api';
+import { WinstonLogger } from '@backstage/backend-app-api';
+import { transports, format } from 'winston';
+import { createConfigSecretEnumerator } from '@backstage/backend-app-api';
+import { loadConfigSchema } from '@backstage/config-loader';
+import { getPackages } from '@manypkg/get-packages';
+import { dynamicPluginsSchemasServiceRef } from './schemas';
+
+/** @public */
+export const dynamicPluginsRootLoggerServiceFactory = createServiceFactory({
+  service: coreServices.rootLogger,
+  deps: {
+    config: coreServices.rootConfig,
+    schemas: dynamicPluginsSchemasServiceRef,
+  },
+  async factory({ config, schemas }) {
+    const logger = WinstonLogger.create({
+      meta: {
+        service: 'backstage',
+      },
+      level: process.env.LOG_LEVEL || 'info',
+      format:
+        process.env.NODE_ENV === 'production'
+          ? format.json()
+          : WinstonLogger.colorFormat(),
+      transports: [new transports.Console()],
+    });
+
+    const configSchema = await loadConfigSchema({
+      dependencies: (
+        await getPackages(process.cwd())
+      ).packages.map(p => p.packageJson.name),
+    });
+
+    const secretEnumerator = await createConfigSecretEnumerator({
+      logger,
+      schema: (await schemas.addDynamicPluginsSchemas(configSchema)).schema,
+    });
+    logger.addRedactions(secretEnumerator(config));
+    config.subscribe?.(() => logger.addRedactions(secretEnumerator(config)));
+
+    return logger;
+  },
+});

packages/backend-dynamic-feature-service/src/schemas/schemas.ts

@@ -0,0 +1,187 @@
+/*
+ * Copyright 2024 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { ScannedPluginPackage } from '../scanner/types';
+import {
+  coreServices,
+  createServiceFactory,
+  createServiceRef,
+} from '@backstage/backend-plugin-api';
+import { findPaths } from '@backstage/cli-common';
+
+import fs from 'fs-extra';
+import * as path from 'path';
+import * as url from 'url';
+import { isEmpty } from 'lodash';
+import { LoggerService } from '@backstage/backend-plugin-api';
+import { JsonObject } from '@backstage/types';
+import { PluginScanner } from '../scanner/plugin-scanner';
+import { ConfigSchema, loadConfigSchema } from '@backstage/config-loader';
+
+/**
+ *
+ * @public
+ * */
+export interface DynamicPluginsSchemasService {
+  addDynamicPluginsSchemas(configSchema: ConfigSchema): Promise<{
+    schema: ConfigSchema;
+  }>;
+}
+
+/**
+ * A service that provides the config schemas of scanned dynamic plugins.
+ *
+ * @public
+ */
+export const dynamicPluginsSchemasServiceRef =
+  createServiceRef<DynamicPluginsSchemasService>({
+    id: 'core.dynamicplugins.schemas',
+    scope: 'root',
+  });
+
+/**
+ * @public
+ */
+export interface DynamicPluginsSchemasOptions {
+  /**
+   * Function that returns the path to the Json schema file for a given scanned plugin package.
+   * The path is either absolute, or relative to the plugin package root directory.
+   *
+   * Default behavior is to look for the `dist/configSchema.json` relative path.
+   *
+   * @param pluginPackage - The scanned plugin package.
+   * @returns the absolute or plugin-relative path to the Json schema file.
+   */
+  schemaLocator?: (pluginPackage: ScannedPluginPackage) => string;
+}
+
+/**
+ * @public
+ */
+export const dynamicPluginsSchemasServiceFactory = createServiceFactory(
+  (options?: DynamicPluginsSchemasOptions) => ({
+    service: dynamicPluginsSchemasServiceRef,
+    deps: {
+      config: coreServices.rootConfig,
+    },
+    factory({ config }) {
+      let additionalSchemas: { [context: string]: JsonObject } | undefined;
+
+      return {
+        async addDynamicPluginsSchemas(configSchema: ConfigSchema): Promise<{
+          schema: ConfigSchema;
+        }> {
+          if (!additionalSchemas) {
+            const logger = {
+              ...console,
+              child() {
+                return this;
+              },
+            };
+
+            const scanner = PluginScanner.create({
+              config,
+              logger,
+              // eslint-disable-next-line no-restricted-syntax
+              backstageRoot: findPaths(__dirname).targetRoot,
+              preferAlpha: true,
+            });
+
+            const { packages } = await scanner.scanRoot();
+
+            additionalSchemas = await gatherDynamicPluginsSchemas(
+              packages,
+              logger,
+              options?.schemaLocator,
+            );
+          }
+
+          const serialized = configSchema.serialize();
+          if (serialized?.backstageConfigSchemaVersion !== 1) {
+            throw new Error(
+              'Serialized configuration schema is invalid or has an invalid version number',
+            );
+          }
+          const schemas = serialized.schemas as {
+            value: JsonObject;
+            path: string;
+          }[];
+
+          schemas.push(
+            ...Object.keys(additionalSchemas).map(context => {
+              return {
+                path: context,
+                value: additionalSchemas![context],
+              };
+            }),
+          );
+          serialized.schemas = schemas;
+          return {
+            schema: await loadConfigSchema({
+              serialized,
+            }),
+          };
+        },
+      };
+    },
+  }),
+);
+
+/** @internal */
+async function gatherDynamicPluginsSchemas(
+  packages: ScannedPluginPackage[],
+  logger: LoggerService,
+  schemaLocator: (pluginPackage: ScannedPluginPackage) => string = () =>
+    path.join('dist', 'configSchema.json'),
+): Promise<{ [context: string]: JsonObject }> {
+  const allSchemas: { [context: string]: JsonObject } = {};
+
+  for (const pluginPackage of packages) {
+    let schemaLocation = schemaLocator(pluginPackage);
+
+    if (!path.isAbsolute(schemaLocation)) {
+      let pluginLocation = url.fileURLToPath(pluginPackage.location);
+      if (path.basename(pluginLocation) === 'alpha') {
+        pluginLocation = path.dirname(pluginLocation);
+      }
+      schemaLocation = path.resolve(pluginLocation, schemaLocation);
+    }
+
+    if (!(await fs.pathExists(schemaLocation))) {
+      continue;
+    }
+
+    const serialized = await fs.readJson(schemaLocation);
+    if (!serialized) {
+      continue;
+    }
+
+    if (isEmpty(serialized)) {
+      continue;
+    }
+
+    if (!serialized?.$schema || serialized?.type !== 'object') {
+      logger.error(
+        `Serialized configuration schema is invalid for plugin ${pluginPackage.manifest.name}`,
+      );
+      continue;
+    }
+
+    allSchemas[schemaLocation] = serialized;
+  }
+
+  return allSchemas;
+}

plugins/app-backend/api-report.md

@@ -4,6 +4,7 @@
 
 ```ts
 import { Config } from '@backstage/config';
+import { ConfigSchema } from '@backstage/config-loader';
 import express from 'express';
 import { Logger } from 'winston';
 import { PluginDatabaseManager } from '@backstage/backend-common';
@@ -20,6 +21,7 @@ export interface RouterOptions {
   disableConfigInjection?: boolean;
   // (undocumented)
   logger: Logger;
+  schema?: ConfigSchema;
   staticFallbackHandler?: express.Handler;
 }
 ```

plugins/app-backend/src/lib/config.ts

@@ -19,7 +19,11 @@ import { resolve as resolvePath } from 'path';
 import { Logger } from 'winston';
 import { AppConfig, Config } from '@backstage/config';
 import { JsonObject } from '@backstage/types';
-import { loadConfigSchema, readEnvConfig } from '@backstage/config-loader';
+import {
+  ConfigSchema,
+  loadConfigSchema,
+  readEnvConfig,
+} from '@backstage/config-loader';
 
 type InjectOptions = {
   appConfigs: AppConfig[];
@@ -74,6 +78,7 @@ type ReadOptions = {
   env: { [name: string]: string | undefined };
   appDistDir: string;
   config: Config;
+  schema?: ConfigSchema;
 };
 
 /**
@@ -90,7 +95,11 @@ export async function readConfigs(options: ReadOptions): Promise<AppConfig[]> {
     const serializedSchema = await fs.readJson(schemaPath);
 
     try {
-      const schema = await loadConfigSchema({ serialized: serializedSchema });
+      const schema =
+        options.schema ||
+        (await loadConfigSchema({
+          serialized: serializedSchema,
+        }));
 
       const frontendConfigs = await schema.process(
         [{ data: config.get() as JsonObject, context: 'app' }],

plugins/app-backend/src/service/appPlugin.ts

@@ -21,7 +21,11 @@ import {
 } from '@backstage/backend-plugin-api';
 import { createRouter } from './router';
 import { loggerToWinstonLogger } from '@backstage/backend-common';
-import { staticFallbackHandlerExtensionPoint } from '@backstage/plugin-app-node';
+import {
+  configSchemaExtensionPoint,
+  staticFallbackHandlerExtensionPoint,
+} from '@backstage/plugin-app-node';
+import { ConfigSchema } from '@backstage/config-loader';
 
 /**
  * The App plugin is responsible for serving the frontend app bundle and static assets.
@@ -31,6 +35,7 @@ export const appPlugin = createBackendPlugin({
   pluginId: 'app',
   register(env) {
     let staticFallbackHandler: express.Handler | undefined;
+    let schema: ConfigSchema | undefined;
 
     env.registerExtensionPoint(staticFallbackHandlerExtensionPoint, {
       setStaticFallbackHandler(handler) {
@@ -43,6 +48,17 @@ export const appPlugin = createBackendPlugin({
       },
     });
 
+    env.registerExtensionPoint(configSchemaExtensionPoint, {
+      setConfigSchema(configSchema) {
+        if (schema) {
+          throw new Error(
+            'Attempted to set config schema for the app-backend twice',
+          );
+        }
+        schema = configSchema;
+      },
+    });
+
     env.registerInit({
       deps: {
         logger: coreServices.logger,
@@ -53,6 +69,7 @@ export const appPlugin = createBackendPlugin({
       async init({ logger, config, database, httpRouter }) {
         const appPackageName =
           config.getOptionalString('app.packageName') ?? 'app';
+
         const winstonLogger = loggerToWinstonLogger(logger);
 
         const router = await createRouter({
@@ -61,6 +78,7 @@ export const appPlugin = createBackendPlugin({
           database,
           appPackageName,
           staticFallbackHandler,
+          schema,
         });
         httpRouter.use(router);
       },

plugins/app-backend/src/service/router.ts

@@ -37,6 +37,7 @@ import {
   CACHE_CONTROL_NO_CACHE,
   CACHE_CONTROL_REVALIDATE_CACHE,
 } from '../lib/headers';
+import { ConfigSchema } from '@backstage/config-loader';
 
 // express uses mime v1 while we only have types for mime v2
 type Mime = { lookup(arg0: string): string };
@@ -85,6 +86,13 @@ export interface RouterOptions {
    * This also disables configuration injection though `APP_CONFIG_` environment variables.
    */
   disableConfigInjection?: boolean;
+
+  /**
+   *
+   * Provides a ConfigSchema.
+   *
+   */
+  schema?: ConfigSchema;
 }
 
 /** @public */
@@ -121,6 +129,7 @@ export async function createRouter(
       config,
       appDistDir,
       env: process.env,
+      schema: options.schema,
     });
 
     injectedConfigPath = await injectConfig({ appConfigs, logger, staticDir });

plugins/app-node/api-report.md

@@ -3,9 +3,23 @@
 > Do not edit this file. It is a report generated by [API Extractor](https://api-extractor.com/).
 
 ```ts
+import { ConfigSchema } from '@backstage/config-loader';
 import { ExtensionPoint } from '@backstage/backend-plugin-api';
 import { Handler } from 'express';
 
+// @public
+export interface ConfigSchemaExtensionPoint {
+  setConfigSchema(configSchema: ConfigSchema): void;
+}
+
+// @public
+export const configSchemaExtensionPoint: ExtensionPoint<ConfigSchemaExtensionPoint>;
+
+// @public
+export function loadCompiledConfigSchema(
+  appDistDir: string,
+): Promise<ConfigSchema | undefined>;
+
 // @public
 export interface StaticFallbackHandlerExtensionPoint {
   setStaticFallbackHandler(handler: Handler): void;

plugins/app-node/package.json

@@ -34,7 +34,9 @@
   ],
   "dependencies": {
     "@backstage/backend-plugin-api": "workspace:^",
+    "@backstage/config-loader": "workspace:^",
     "@types/express": "^4.17.6",
-    "express": "^4.17.1"
+    "express": "^4.17.1",
+    "fs-extra": "10.1.0"
   }
 }

plugins/app-node/src/extensions.ts

@@ -15,6 +15,7 @@
  */
 
 import { createExtensionPoint } from '@backstage/backend-plugin-api';
+import { ConfigSchema } from '@backstage/config-loader';
 import { Handler } from 'express';
 
 /**
@@ -50,3 +51,25 @@ export const staticFallbackHandlerExtensionPoint =
   createExtensionPoint<StaticFallbackHandlerExtensionPoint>({
     id: 'app.staticFallbackHandler',
   });
+
+/**
+ * The interface for {@link configSchemaExtensionPoint}.
+ *
+ * @public
+ */
+export interface ConfigSchemaExtensionPoint {
+  /**
+   * Sets the config schema. This can only be done once.
+   */
+  setConfigSchema(configSchema: ConfigSchema): void;
+}
+
+/**
+ * An extension point the exposes the ability to override the config schema used by the frontend application.
+ *
+ * @public
+ */
+export const configSchemaExtensionPoint =
+  createExtensionPoint<ConfigSchemaExtensionPoint>({
+    id: 'app.configSchema',
+  });

plugins/app-node/src/index.ts

@@ -23,4 +23,8 @@
 export {
   staticFallbackHandlerExtensionPoint,
   type StaticFallbackHandlerExtensionPoint,
+  configSchemaExtensionPoint,
+  type ConfigSchemaExtensionPoint,
 } from './extensions';
+
+export { loadCompiledConfigSchema } from './schema';

plugins/app-node/src/schema.ts

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2024 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import fs from 'fs-extra';
+import { resolve as resolvePath } from 'path';
+import { ConfigSchema, loadConfigSchema } from '@backstage/config-loader';
+
+/**
+ * Loads the config schema that is embedded in the frontend build.
+ *
+ * @public
+ */
+export async function loadCompiledConfigSchema(
+  appDistDir: string,
+): Promise<ConfigSchema | undefined> {
+  const schemaPath = resolvePath(appDistDir, '.config-schema.json');
+  if (await fs.pathExists(schemaPath)) {
+    const serializedSchema = await fs.readJson(schemaPath);
+
+    return await loadConfigSchema({
+      serialized: serializedSchema,
+    });
+  }
+
+  return undefined;
+}

scripts/verify-local-dependencies.js

@@ -90,6 +90,7 @@ const roleRules = [
       '@backstage/backend-common',
       '@backstage/backend-defaults',
       '@backstage/backend-test-utils',
+      '@backstage/backend-dynamic-feature-service',
     ],
     message: `Plugin package SOURCE_NAME with role SOURCE_ROLE has a runtime dependency on package TARGET_NAME, which is not permitted. If you are using this dependency for dev server purposes, you can move it to devDependencies instead.`,
   },

yarn.lock

@@ -3383,6 +3383,7 @@ __metadata:
     "@backstage/config": "workspace:^"
     "@backstage/config-loader": "workspace:^"
     "@backstage/errors": "workspace:^"
+    "@backstage/plugin-app-node": "workspace:^"
     "@backstage/plugin-auth-node": "workspace:^"
     "@backstage/plugin-catalog-backend": "workspace:^"
     "@backstage/plugin-events-backend": "workspace:^"
@@ -3393,9 +3394,11 @@ __metadata:
     "@backstage/plugin-search-backend-node": "workspace:^"
     "@backstage/plugin-search-common": "workspace:^"
     "@backstage/types": "workspace:^"
+    "@manypkg/get-packages": ^1.1.3
     "@types/express": ^4.17.6
     chokidar: ^3.5.3
     express: ^4.17.1
+    fs-extra: 10.1.0
     lodash: ^4.17.21
     wait-for-expect: ^3.0.2
     winston: ^3.2.1
@@ -4647,8 +4650,10 @@ __metadata:
   dependencies:
     "@backstage/backend-plugin-api": "workspace:^"
     "@backstage/cli": "workspace:^"
+    "@backstage/config-loader": "workspace:^"
     "@types/express": ^4.17.6
     express: ^4.17.1
+    fs-extra: 10.1.0
   languageName: unknown
   linkType: soft