plugins/app-backend: add env config injection

plugins/app-backend/package.json

@@ -22,9 +22,11 @@
   },
   "dependencies": {
     "@backstage/backend-common": "^0.1.1-alpha.18",
+    "@backstage/config-loader": "^0.1.1-alpha.18",
     "@types/express": "^4.17.6",
     "express": "^4.17.1",
     "express-promise-router": "^3.0.3",
+    "fs-extra": "^9.0.0",
     "winston": "^3.2.1",
     "yn": "^4.0.0"
   },

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

@@ -0,0 +1,136 @@
+/*
+ * 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 fs from 'fs-extra';
+import { resolve as resolvePath } from 'path';
+import { getVoidLogger } from '@backstage/backend-common';
+import { injectEnvConfig } from './config';
+
+jest.mock('fs-extra');
+
+const fsMock = fs as jest.Mocked<typeof fs>;
+const readFileMock = (fsMock.readFile as unknown) as jest.MockedFunction<
+  (name: string) => Promise<string>
+>;
+
+const MOCK_DIR = 'mock-dir';
+
+const baseOptions = {
+  env: {},
+  staticDir: MOCK_DIR,
+  logger: getVoidLogger(),
+};
+
+describe('injectEnvConfig', () => {
+  beforeEach(() => {
+    fsMock.readdir.mockResolvedValue(['main.js']);
+  });
+
+  afterEach(() => {
+    jest.resetAllMocks();
+  });
+
+  it('should not inject without config', async () => {
+    await injectEnvConfig(baseOptions);
+    expect(fsMock.readdir).toHaveBeenCalledTimes(0);
+    expect(fsMock.readFile).toHaveBeenCalledTimes(0);
+    expect(fsMock.writeFile).toHaveBeenCalledTimes(0);
+  });
+
+  it('should find the correct file to inject', async () => {
+    fsMock.readdir.mockResolvedValue([
+      'before.js',
+      'not-js.txt',
+      'main.js',
+      'after.js',
+    ]);
+    readFileMock.mockImplementation(async (file: string) => {
+      if (file.endsWith('main.js')) {
+        return '"__APP_INJECTED_RUNTIME_CONFIG__"';
+      }
+      return 'NO_PLACEHOLDER_HERE';
+    });
+
+    await injectEnvConfig({ ...baseOptions, env: { APP_CONFIG_x: '0' } });
+    expect(fsMock.readFile).toHaveBeenCalledTimes(2);
+    expect(fsMock.readFile).toHaveBeenNthCalledWith(
+      1,
+      resolvePath(MOCK_DIR, 'before.js'),
+      'utf8',
+    );
+    expect(fsMock.readFile).toHaveBeenNthCalledWith(
+      2,
+      resolvePath(MOCK_DIR, 'main.js'),
+      'utf8',
+    );
+
+    expect(fsMock.writeFile).toHaveBeenCalledTimes(1);
+    expect(fsMock.writeFile).toHaveBeenCalledWith(
+      resolvePath(MOCK_DIR, 'main.js'),
+      '/*__APP_INJECTED_CONFIG_MARKER__*/"{\\"x\\":0}"/*__INJECTED_END__*/',
+      'utf8',
+    );
+
+    // eslint-disable-next-line no-eval
+    expect(JSON.parse(eval(fsMock.writeFile.mock.calls[0][1]))).toEqual({
+      x: 0,
+    });
+  });
+
+  it('should re-inject config', async () => {
+    fsMock.readdir.mockResolvedValue(['main.js']);
+    readFileMock.mockResolvedValue(
+      'JSON.parse("__APP_INJECTED_RUNTIME_CONFIG__")',
+    );
+
+    await injectEnvConfig({
+      ...baseOptions,
+      env: {
+        APP_CONFIG_x: '0',
+      },
+    });
+
+    expect(fsMock.writeFile).toHaveBeenCalledTimes(1);
+    expect(fsMock.writeFile).toHaveBeenCalledWith(
+      resolvePath(MOCK_DIR, 'main.js'),
+      'JSON.parse(/*__APP_INJECTED_CONFIG_MARKER__*/"{\\"x\\":0}"/*__INJECTED_END__*/)',
+      'utf8',
+    );
+
+    // eslint-disable-next-line no-eval
+    expect(eval(fsMock.writeFile.mock.calls[0][1])).toEqual({ x: 0 });
+
+    readFileMock.mockResolvedValue(fsMock.writeFile.mock.calls[0][1]);
+
+    await injectEnvConfig({
+      ...baseOptions,
+      env: {
+        APP_CONFIG_x: '1',
+        APP_CONFIG_y: '2',
+      },
+    });
+
+    expect(fsMock.writeFile).toHaveBeenCalledTimes(2);
+    expect(fsMock.writeFile).toHaveBeenLastCalledWith(
+      resolvePath(MOCK_DIR, 'main.js'),
+      'JSON.parse(/*__APP_INJECTED_CONFIG_MARKER__*/"{\\"x\\":1,\\"y\\":2}"/*__INJECTED_END__*/)',
+      'utf8',
+    );
+
+    // eslint-disable-next-line no-eval
+    expect(eval(fsMock.writeFile.mock.calls[1][1])).toEqual({ x: 1, y: 2 });
+  });
+});

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

@@ -0,0 +1,74 @@
+/*
+ * 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 fs from 'fs-extra';
+import { resolve as resolvePath } from 'path';
+import { readEnvConfig } from '@backstage/config-loader';
+import { Logger } from 'winston';
+
+type Options = {
+  // Environment to read config from
+  env: { [name: string]: string | undefined };
+  // Directory of the static JS files to search for file to inject
+  staticDir: string;
+  logger: Logger;
+};
+
+/**
+ * Injects config from APP_CONFIG_ env vars, replacing existing
+ * injected config if it has already been injected.
+ */
+export async function injectEnvConfig(options: Options) {
+  const { env, staticDir, logger } = options;
+
+  const envConfig = readEnvConfig(env);
+  if (envConfig.length === 0) {
+    return;
+  }
+
+  const files = await fs.readdir(staticDir);
+  const jsFiles = files.filter(file => file.endsWith('.js'));
+
+  const [{ data }] = envConfig;
+  const escapedData = JSON.stringify(data).replace(/("|'|\\)/g, '\\$1');
+  const injected = `/*__APP_INJECTED_CONFIG_MARKER__*/"${escapedData}"/*__INJECTED_END__*/`;
+
+  for (const jsFile of jsFiles) {
+    const path = resolvePath(staticDir, jsFile);
+
+    const content = await fs.readFile(path, 'utf8');
+    if (content.includes('__APP_INJECTED_RUNTIME_CONFIG__')) {
+      logger.info(`Injecting env config into ${jsFile}`);
+
+      const newContent = content.replace(
+        '"__APP_INJECTED_RUNTIME_CONFIG__"',
+        injected,
+      );
+      await fs.writeFile(path, newContent, 'utf8');
+      return;
+    } else if (content.includes('__APP_INJECTED_CONFIG_MARKER__')) {
+      logger.info(`Replacing injected env config in ${jsFile}`);
+
+      const newContent = content.replace(
+        /\/\*__APP_INJECTED_CONFIG_MARKER__\*\/.*\/\*__INJECTED_END__\*\//,
+        injected,
+      );
+      await fs.writeFile(path, newContent, 'utf8');
+      return;
+    }
+  }
+  logger.info('Env config not injected');
+}

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

@@ -22,6 +22,8 @@ import request from 'supertest';
 
 import { createRouter } from './router';
 
+jest.mock('../lib/config', () => ({ injectEnvConfig: jest.fn() }));
+
 global.__non_webpack_require__ = {
   resolve: () => resolvePath(__dirname, '__fixtures__/app-dir/package.json'),
 };

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

@@ -19,6 +19,7 @@ import { notFoundHandler } from '@backstage/backend-common';
 import express from 'express';
 import Router from 'express-promise-router';
 import { Logger } from 'winston';
+import { injectEnvConfig } from '../lib/config';
 
 export interface RouterOptions {
   logger: Logger;
@@ -37,6 +38,12 @@ export async function createRouter(
   );
   options.logger.info(`Serving static app content from ${appDistDir}`);
 
+  await injectEnvConfig({
+    env: process.env,
+    logger: options.logger,
+    staticDir: resolvePath(appDistDir, 'static'),
+  });
+
   const router = Router();
 
   // Use a separate router for static content so that a fallback can be provided by backend