plugins: add initial app-backend

plugins/app-backend/.eslintrc.js

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+module.exports = {
+  extends: [require.resolve('@backstage/cli/config/eslint.backend')],
+};

plugins/app-backend/README.md

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+# App backend plugin
+
+This backend plugin can be installed to serve static content of a Backstage app.

plugins/app-backend/package.json

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+{
+  "name": "@backstage/plugin-app-backend",
+  "version": "0.1.1-alpha.18",
+  "main": "src/index.ts",
+  "types": "src/index.ts",
+  "license": "Apache-2.0",
+  "private": true,
+  "publishConfig": {
+    "access": "public",
+    "main": "dist/index.cjs.js",
+    "types": "dist/index.d.ts"
+  },
+  "scripts": {
+    "start": "backstage-cli backend:dev",
+    "build": "backstage-cli backend:build",
+    "lint": "backstage-cli lint",
+    "test": "backstage-cli test",
+    "prepack": "backstage-cli prepack",
+    "postpack": "backstage-cli postpack",
+    "clean": "backstage-cli clean",
+    "mock-data": "./scripts/mock-data.sh"
+  },
+  "dependencies": {
+    "@backstage/backend-common": "^0.1.1-alpha.18",
+    "@types/express": "^4.17.6",
+    "express": "^4.17.1",
+    "express-promise-router": "^3.0.3",
+    "winston": "^3.2.1",
+    "yn": "^4.0.0"
+  },
+  "devDependencies": {
+    "@backstage/cli": "^0.1.1-alpha.18",
+    "@types/supertest": "^2.0.8",
+    "msw": "^0.19.5",
+    "supertest": "^4.0.2"
+  },
+  "files": [
+    "dist",
+    "static"
+  ]
+}

plugins/app-backend/scripts/mock-data.sh

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+#!/usr/bin/env bash
+echo "use this script to load your service with some mock data if needed!"

plugins/app-backend/src/index.ts

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+/*
+ * Copyright 2020 Spotify AB
+ *
+ * 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 * from './service/router';

plugins/app-backend/src/run.ts

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+/*
+ * Copyright 2020 Spotify AB
+ *
+ * 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 { getRootLogger } from '@backstage/backend-common';
+import yn from 'yn';
+import { startStandaloneServer } from './service/standaloneServer';
+
+const port = process.env.PLUGIN_PORT ? Number(process.env.PLUGIN_PORT) : 7000;
+const enableCors = yn(process.env.PLUGIN_CORS, { default: false });
+const logger = getRootLogger();
+
+startStandaloneServer({ port, enableCors, logger }).catch(err => {
+  logger.error(err);
+  process.exit(1);
+});
+
+process.on('SIGINT', () => {
+  logger.info('CTRL+C pressed; exiting.');
+  process.exit(0);
+});

plugins/app-backend/src/service/__fixtures__/app-dir/.gitignore

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+!dist

plugins/app-backend/src/service/__fixtures__/app-dir/dist/index.html

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+this is index.html

plugins/app-backend/src/service/__fixtures__/app-dir/dist/other.html

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+this is other.html

plugins/app-backend/src/service/__fixtures__/app-dir/dist/static/main.txt

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+this is main.txt

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

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+/*
+ * Copyright 2020 Spotify AB
+ *
+ * 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 { resolve as resolvePath } from 'path';
+import { getVoidLogger } from '@backstage/backend-common';
+import express from 'express';
+import Router from 'express-promise-router';
+import request from 'supertest';
+
+import { createRouter } from './router';
+
+global.__non_webpack_require__ = {
+  resolve: () => resolvePath(__dirname, '__fixtures__/app-dir/package.json'),
+};
+
+describe('createRouter', () => {
+  let app: express.Express;
+
+  beforeAll(async () => {
+    const router = await createRouter({
+      logger: getVoidLogger(),
+      appPackageName: 'example-app',
+    });
+    app = express().use(router);
+  });
+
+  beforeEach(() => {
+    jest.resetAllMocks();
+  });
+
+  it('returns index.html', async () => {
+    const response = await request(app).get('/index.html');
+
+    expect(response.status).toBe(200);
+    expect(response.text).toBe('this is index.html\n');
+  });
+
+  it('returns other.html', async () => {
+    const response = await request(app).get('/other.html');
+
+    expect(response.status).toBe(200);
+    expect(response.text).toBe('this is other.html\n');
+  });
+
+  it('returns index.html if missing', async () => {
+    const response = await request(app).get('/missing.html');
+
+    expect(response.status).toBe(200);
+    expect(response.text).toBe('this is index.html\n');
+  });
+});
+
+describe('createRouter with static fallback handler', () => {
+  it('uses static fallback handler', async () => {
+    const staticFallbackHandler = Router();
+
+    staticFallbackHandler.get('/test.txt', (_req, res) => {
+      res.end('this is test.txt');
+    });
+
+    const router = await createRouter({
+      logger: getVoidLogger(),
+      appPackageName: 'example-app',
+      staticFallbackHandler,
+    });
+
+    const app = express().use(router);
+
+    const response1 = await request(app).get('/static/main.txt');
+    expect(response1.status).toBe(200);
+    expect(response1.text).toBe('this is main.txt\n');
+
+    const response2 = await request(app).get('/static/test.txt');
+    expect(response2.status).toBe(200);
+    expect(response2.text).toBe('this is test.txt');
+
+    const response3 = await request(app).get('/static/missing.txt');
+    expect(response3.status).toBe(404);
+  });
+});

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

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+/*
+ * Copyright 2020 Spotify AB
+ *
+ * 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 { resolve as resolvePath, dirname } from 'path';
+import { notFoundHandler } from '@backstage/backend-common';
+import express from 'express';
+import Router from 'express-promise-router';
+import { Logger } from 'winston';
+
+export interface RouterOptions {
+  logger: Logger;
+  appPackageName?: string;
+  staticFallbackHandler?: express.Handler;
+}
+
+export async function createRouter(
+  options: RouterOptions,
+): Promise<express.Router> {
+  const appDistDir = resolvePath(
+    dirname(
+      __non_webpack_require__.resolve(`${options.appPackageName}/package.json`),
+    ),
+    'dist',
+  );
+  options.logger.info(`Serving static app content from ${appDistDir}`);
+
+  const router = Router();
+
+  // Use a separate router for static content so that a fallback can be provided by backend
+  const staticRouter = Router();
+  staticRouter.use(express.static(resolvePath(appDistDir, 'static')));
+  if (options.staticFallbackHandler) {
+    staticRouter.use(options.staticFallbackHandler);
+  }
+  staticRouter.use(notFoundHandler());
+
+  router.use('/static', staticRouter);
+  router.use(express.static(appDistDir));
+  router.get('/*', (_req, res) => {
+    res.sendFile(resolvePath(appDistDir, 'index.html'));
+  });
+
+  return router;
+}

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

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+/*
+ * Copyright 2020 Spotify AB
+ *
+ * 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 { createServiceBuilder } from '@backstage/backend-common';
+import { Server } from 'http';
+import { Logger } from 'winston';
+import { createRouter } from './router';
+
+export interface ServerOptions {
+  port: number;
+  enableCors: boolean;
+  logger: Logger;
+}
+
+export async function startStandaloneServer(
+  options: ServerOptions,
+): Promise<Server> {
+  const logger = options.logger.child({ service: 'app-backend' });
+  logger.debug('Starting application server...');
+  const router = await createRouter({
+    logger,
+    appPackageName: 'example-app',
+  });
+
+  const service = createServiceBuilder(module).addRouter('', router);
+
+  return await service.start().catch(err => {
+    logger.error(err);
+    process.exit(1);
+  });
+}
+
+module.hot?.accept();

plugins/app-backend/src/setupTests.ts

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+/*
+ * Copyright 2020 Spotify AB
+ *
+ * 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 {};