From a1a60ad9d1563d36483d2b293eb53fcfc49f17de Mon Sep 17 00:00:00 2001
From: Ivan Shmidt <bahoc47@gmail.com>
Date: Thu, 11 Jun 2020 02:51:06 +0200
Subject: [PATCH] feat: hmr logic for the backend

---
 packages/backend-common/package.json          |  3 ++
 packages/backend-common/src/hot.ts            | 51 +++++++++++++++++++
 packages/backend-common/src/index.ts          |  1 +
 .../src/service/ServiceBuilderImpl.ts         | 26 ++++++++--
 .../src/service/createServiceBuilder.ts       |  4 +-
 packages/backend-common/tsconfig.json         |  2 +-
 packages/backend/src/index.ts                 | 23 ++++++---
 packages/backend/src/plugins/catalog.ts       |  5 +-
 packages/backend/tsconfig.json                |  2 +-
 packages/cli/src/lib/bundler/config.ts        | 13 ++---
 plugins/auth-backend/tsconfig.json            |  2 +-
 .../src/service/standaloneServer.ts           |  4 +-
 plugins/catalog-backend/tsconfig.json         |  2 +-
 plugins/identity-backend/tsconfig.json        |  2 +-
 plugins/sentry-backend/tsconfig.json          |  2 +-
 yarn.lock                                     | 17 +++++++
 16 files changed, 131 insertions(+), 28 deletions(-)
 create mode 100644 packages/backend-common/src/hot.ts

diff --git a/packages/backend-common/package.json b/packages/backend-common/package.json
index 54202975c3..b7d5cf7c11 100644
--- a/packages/backend-common/package.json
+++ b/packages/backend-common/package.json
@@ -27,11 +27,13 @@
     "clean": "backstage-cli clean"
   },
   "dependencies": {
+    "@types/stoppable": "^1.1.0",
     "compression": "^1.7.4",
     "cors": "^2.8.5",
     "express": "^4.17.1",
     "helmet": "^3.22.0",
     "morgan": "^1.10.0",
+    "stoppable": "^1.1.0",
     "winston": "^3.2.1"
   },
   "devDependencies": {
@@ -42,6 +44,7 @@
     "@types/http-errors": "^1.6.3",
     "@types/morgan": "^1.9.0",
     "@types/supertest": "^2.0.8",
+    "@types/webpack-env": "^1.15.2",
     "@types/yaml": "^1.9.7",
     "get-port": "^5.1.1",
     "http-errors": "^1.7.3",
diff --git a/packages/backend-common/src/hot.ts b/packages/backend-common/src/hot.ts
new file mode 100644
index 0000000000..3043bcb681
--- /dev/null
+++ b/packages/backend-common/src/hot.ts
@@ -0,0 +1,51 @@
+/*
+ * 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 function useHotEffect(
+  _module: NodeModule,
+  effectFactory: () => () => void,
+) {
+  const cancelEffect = effectFactory();
+  if (_module.hot) {
+    _module.hot.addDisposeHandler(() => {
+      cancelEffect();
+    });
+  }
+}
+
+export function useHotMemoize<T>(
+  _module: NodeModule,
+  valueFactory: () => T,
+): T {
+  if (!_module.hot) {
+    return valueFactory();
+  }
+  const index = (useHotMemoize as any).index ?? 0;
+  (useHotMemoize as any).index += 1;
+  const prevValue = _module.hot?.data?.[index];
+  if (prevValue) {
+    _module.hot!.addDisposeHandler(data => {
+      data[index] = prevValue;
+    });
+    return prevValue;
+  }
+  const newValue = valueFactory();
+  if (_module.hot) {
+    _module.hot.addDisposeHandler(data => {
+      data[index] = newValue;
+    });
+  }
+  return newValue;
+}
diff --git a/packages/backend-common/src/index.ts b/packages/backend-common/src/index.ts
index 11689aafff..0e4e5b2c6b 100644
--- a/packages/backend-common/src/index.ts
+++ b/packages/backend-common/src/index.ts
@@ -18,3 +18,4 @@ export * from './errors';
 export * from './logging';
 export * from './middleware';
 export * from './service';
+export * from './hot';
diff --git a/packages/backend-common/src/service/ServiceBuilderImpl.ts b/packages/backend-common/src/service/ServiceBuilderImpl.ts
index ac35d52112..844990a39d 100644
--- a/packages/backend-common/src/service/ServiceBuilderImpl.ts
+++ b/packages/backend-common/src/service/ServiceBuilderImpl.ts
@@ -19,6 +19,7 @@ import cors from 'cors';
 import express, { Router } from 'express';
 import helmet from 'helmet';
 import { Server } from 'http';
+import stoppable from 'stoppable';
 import { Logger } from 'winston';
 import { getRootLogger } from '../logging';
 import {
@@ -27,6 +28,7 @@ import {
   requestLoggingHandler,
 } from '../middleware';
 import { ServiceBuilder } from './types';
+import { useHotEffect } from '../hot';
 
 const DEFAULT_PORT = 7000;
 
@@ -35,9 +37,14 @@ export class ServiceBuilderImpl implements ServiceBuilder {
   private logger: Logger | undefined;
   private corsOptions: cors.CorsOptions | undefined;
   private routers: [string, Router][];
-
-  constructor() {
+  /**
+   * Reference to the module where builder is created
+   * Needed for the HMR
+   */
+  private module: NodeModule;
+  constructor(module: NodeModule) {
     this.routers = [];
+    this.module = module;
   }
 
   setPort(port: number): ServiceBuilder {
@@ -82,9 +89,20 @@ export class ServiceBuilderImpl implements ServiceBuilder {
         logger.error(`Failed to start up on port ${port}, ${e}`);
         reject(e);
       });
-      const server = app.listen(port, () => {
-        logger.info(`Listening on port ${port}`);
+      const server = stoppable(
+        app.listen(port, () => {
+          logger.info(`Listening on port ${port}`);
+        }),
+        0,
+      );
+
+      useHotEffect(this.module, () => {
+        return () =>
+          server.stop((e: any) => {
+            if (e) console.error(e);
+          });
       });
+
       resolve(server);
     });
   }
diff --git a/packages/backend-common/src/service/createServiceBuilder.ts b/packages/backend-common/src/service/createServiceBuilder.ts
index ffd8901def..daef612fcf 100644
--- a/packages/backend-common/src/service/createServiceBuilder.ts
+++ b/packages/backend-common/src/service/createServiceBuilder.ts
@@ -19,6 +19,6 @@ import { ServiceBuilderImpl } from './ServiceBuilderImpl';
 /**
  * Creates a new service builder.
  */
-export function createServiceBuilder() {
-  return new ServiceBuilderImpl();
+export function createServiceBuilder(_module: NodeModule) {
+  return new ServiceBuilderImpl(_module);
 }
diff --git a/packages/backend-common/tsconfig.json b/packages/backend-common/tsconfig.json
index ca39bf9964..2e645bef0b 100644
--- a/packages/backend-common/tsconfig.json
+++ b/packages/backend-common/tsconfig.json
@@ -9,6 +9,6 @@
     "target": "ES2019",
     "module": "commonjs",
     "esModuleInterop": true,
-    "types": ["node", "jest"]
+    "types": ["node", "jest", "webpack-env"]
   }
 }
diff --git a/packages/backend/src/index.ts b/packages/backend/src/index.ts
index 0f0733a8ec..09e244545b 100644
--- a/packages/backend/src/index.ts
+++ b/packages/backend/src/index.ts
@@ -22,7 +22,11 @@
  * Happy hacking!
  */
 
-import { createServiceBuilder, getRootLogger } from '@backstage/backend-common';
+import {
+  createServiceBuilder,
+  getRootLogger,
+  useHotMemoize,
+} from '@backstage/backend-common';
 import knex from 'knex';
 import auth from './plugins/auth';
 import catalog from './plugins/catalog';
@@ -45,19 +49,24 @@ function createEnv(plugin: string): PluginEnvironment {
 }
 
 async function main() {
-  const service = createServiceBuilder()
+  const catalogEnv = useHotMemoize(module, () => createEnv('catalog'));
+  const scaffolderEnv = useHotMemoize(module, () => createEnv('scaffolder'));
+  const authEnv = useHotMemoize(module, () => createEnv('auth'));
+  const identityEnv = useHotMemoize(module, () => createEnv('identity'));
+
+  const service = createServiceBuilder(module)
     .enableCors({
       origin: 'http://localhost:3000',
       credentials: true,
     })
-    .addRouter('/catalog', await catalog(createEnv('catalog')))
-    .addRouter('/scaffolder', await scaffolder(createEnv('scaffolder')))
+    .addRouter('/catalog', await catalog(catalogEnv))
+    .addRouter('/scaffolder', await scaffolder(scaffolderEnv))
     .addRouter(
       '/sentry',
       await sentry(getRootLogger().child({ type: 'plugin', plugin: 'sentry' })),
     )
-    .addRouter('/auth', await auth(createEnv('auth')))
-    .addRouter('/identity', await identity(createEnv('identity')));
+    .addRouter('/auth', await auth(authEnv))
+    .addRouter('/identity', await identity(identityEnv));
 
   await service.start().catch(err => {
     console.log(err);
@@ -66,3 +75,5 @@ async function main() {
 }
 
 main();
+
+module.hot?.accept();
diff --git a/packages/backend/src/plugins/catalog.ts b/packages/backend/src/plugins/catalog.ts
index 8d8ac5b47b..a9e4fa8ce6 100644
--- a/packages/backend/src/plugins/catalog.ts
+++ b/packages/backend/src/plugins/catalog.ts
@@ -24,6 +24,7 @@ import {
   runPeriodically,
 } from '@backstage/plugin-catalog-backend';
 import { PluginEnvironment } from '../types';
+import { useHotEffect } from '@backstage/backend-common';
 
 export default async function createPlugin({
   logger,
@@ -41,7 +42,9 @@ export default async function createPlugin({
     logger,
   );
 
-  runPeriodically(() => higherOrderOperation.refreshAllLocations(), 10000);
+  useHotEffect(module, () =>
+    runPeriodically(() => higherOrderOperation.refreshAllLocations(), 10000),
+  );
 
   return await createRouter({
     entitiesCatalog,
diff --git a/packages/backend/tsconfig.json b/packages/backend/tsconfig.json
index 04701a5502..269b22607c 100644
--- a/packages/backend/tsconfig.json
+++ b/packages/backend/tsconfig.json
@@ -10,6 +10,6 @@
     "module": "commonjs",
     "esModuleInterop": true,
     "lib": ["es2019", "dom"],
-    "types": ["node", "jest"]
+    "types": ["node", "jest", "webpack-env"]
   }
 }
diff --git a/packages/cli/src/lib/bundler/config.ts b/packages/cli/src/lib/bundler/config.ts
index 241ef6a9af..0b664f7cf3 100644
--- a/packages/cli/src/lib/bundler/config.ts
+++ b/packages/cli/src/lib/bundler/config.ts
@@ -87,17 +87,11 @@ export function createConfig(
     externals: [
       nodeExternals({
         modulesDir: paths.rootNodeModules,
-        whitelist: [
-          'webpack/hot/poll?100',
-          /\@backstage\/.*\/(?!node_modules)/,
-        ],
+        whitelist: ['webpack/hot/poll?100', /\@backstage\/.*/],
       }),
       nodeExternals({
         modulesDir: paths.targetNodeModules,
-        whitelist: [
-          'webpack/hot/poll?100',
-          /\@backstage\/.*\/(?!node_modules)/,
-        ],
+        whitelist: ['webpack/hot/poll?100', /\@backstage\/.*/],
       }),
     ],
     target: 'node' as const,
@@ -141,6 +135,9 @@ export function createConfig(
     resolve: {
       extensions: ['.ts', '.tsx', '.mjs', '.js', '.jsx'],
       mainFields: ['main:src', 'browser', 'module', 'main'],
+      ...(isBackend
+        ? { modules: [paths.targetNodeModules, paths.rootNodeModules] }
+        : {}),
       plugins: [
         new ModuleScopePlugin(
           [paths.targetSrc, paths.targetDev],
diff --git a/plugins/auth-backend/tsconfig.json b/plugins/auth-backend/tsconfig.json
index 015a967f76..6f1acf8dce 100644
--- a/plugins/auth-backend/tsconfig.json
+++ b/plugins/auth-backend/tsconfig.json
@@ -10,6 +10,6 @@
     "module": "commonjs",
     "esModuleInterop": true,
     "lib": ["es2019"],
-    "types": ["node", "jest"]
+    "types": ["node", "jest", "webpack-env"]
   }
 }
diff --git a/plugins/catalog-backend/src/service/standaloneServer.ts b/plugins/catalog-backend/src/service/standaloneServer.ts
index f19dfaf282..93c8b86779 100644
--- a/plugins/catalog-backend/src/service/standaloneServer.ts
+++ b/plugins/catalog-backend/src/service/standaloneServer.ts
@@ -54,7 +54,7 @@ export async function startStandaloneServer(
     higherOrderOperation,
     logger,
   });
-  const service = createServiceBuilder()
+  const service = createServiceBuilder(module)
     .enableCors({ origin: 'http://localhost:3000' })
     .addRouter('/catalog', router);
   return await service.start().catch(err => {
@@ -62,3 +62,5 @@ export async function startStandaloneServer(
     process.exit(1);
   });
 }
+
+module.hot?.accept();
diff --git a/plugins/catalog-backend/tsconfig.json b/plugins/catalog-backend/tsconfig.json
index 015a967f76..6f1acf8dce 100644
--- a/plugins/catalog-backend/tsconfig.json
+++ b/plugins/catalog-backend/tsconfig.json
@@ -10,6 +10,6 @@
     "module": "commonjs",
     "esModuleInterop": true,
     "lib": ["es2019"],
-    "types": ["node", "jest"]
+    "types": ["node", "jest", "webpack-env"]
   }
 }
diff --git a/plugins/identity-backend/tsconfig.json b/plugins/identity-backend/tsconfig.json
index 015a967f76..6f1acf8dce 100644
--- a/plugins/identity-backend/tsconfig.json
+++ b/plugins/identity-backend/tsconfig.json
@@ -10,6 +10,6 @@
     "module": "commonjs",
     "esModuleInterop": true,
     "lib": ["es2019"],
-    "types": ["node", "jest"]
+    "types": ["node", "jest", "webpack-env"]
   }
 }
diff --git a/plugins/sentry-backend/tsconfig.json b/plugins/sentry-backend/tsconfig.json
index 015a967f76..6f1acf8dce 100644
--- a/plugins/sentry-backend/tsconfig.json
+++ b/plugins/sentry-backend/tsconfig.json
@@ -10,6 +10,6 @@
     "module": "commonjs",
     "esModuleInterop": true,
     "lib": ["es2019"],
-    "types": ["node", "jest"]
+    "types": ["node", "jest", "webpack-env"]
   }
 }
diff --git a/yarn.lock b/yarn.lock
index 107ba84663..343d9ef3dc 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -4025,6 +4025,13 @@
   dependencies:
     "@types/webpack" "*"
 
+"@types/stoppable@^1.1.0":
+  version "1.1.0"
+  resolved "https://registry.npmjs.org/@types/stoppable/-/stoppable-1.1.0.tgz#a5fa6a48120b109ca9233eed05c67c50bc4f3b91"
+  integrity sha512-BRR23Q9CJduH7AM6mk4JRttd8XyFkb4qIPZu4mdLF+VoP+wcjIxIWIKiBbN78NBbEuynrAyMPtzOHnIp2B/JPQ==
+  dependencies:
+    "@types/node" "*"
+
 "@types/styled-jsx@^2.2.8":
   version "2.2.8"
   resolved "https://registry.npmjs.org/@types/styled-jsx/-/styled-jsx-2.2.8.tgz#b50d13d8a3c34036282d65194554cf186bab7234"
@@ -4148,6 +4155,11 @@
   resolved "https://registry.npmjs.org/@types/webpack-env/-/webpack-env-1.15.1.tgz#c8e84705e08eed430b5e15b39c65b0944e4d1422"
   integrity sha512-eWN5ElDTeBc5lRDh95SqA8x18D0ll2pWudU3uWiyfsRmIZcmUXpEsxPU+7+BsdCrO2vfLRC629u/MmjbmF+2tA==
 
+"@types/webpack-env@^1.15.2":
+  version "1.15.2"
+  resolved "https://registry.npmjs.org/@types/webpack-env/-/webpack-env-1.15.2.tgz#927997342bb9f4a5185a86e6579a0a18afc33b0a"
+  integrity sha512-67ZgZpAlhIICIdfQrB5fnDvaKFcDxpKibxznfYRVAT4mQE41Dido/3Ty+E3xGBmTogc5+0Qb8tWhna+5B8z1iQ==
+
 "@types/webpack-node-externals@^1.7.1":
   version "1.7.1"
   resolved "https://registry.npmjs.org/@types/webpack-node-externals/-/webpack-node-externals-1.7.1.tgz#73d0d7ae0e98cfbd69b7443388302cd69217494a"
@@ -17284,6 +17296,11 @@ stealthy-require@^1.1.1:
   resolved "https://registry.npmjs.org/stealthy-require/-/stealthy-require-1.1.1.tgz#35b09875b4ff49f26a777e509b3090a3226bf24b"
   integrity sha1-NbCYdbT/SfJqd35QmzCQoyJr8ks=
 
+stoppable@^1.1.0:
+  version "1.1.0"
+  resolved "https://registry.npmjs.org/stoppable/-/stoppable-1.1.0.tgz#32da568e83ea488b08e4d7ea2c3bcc9d75015d5b"
+  integrity sha512-KXDYZ9dszj6bzvnEMRYvxgeTHU74QBFL54XKtP3nyMuJ81CFYtABZ3bAzL2EdFUaEwJOBOgENyFj3R7oTzDyyw==
+
 store2@^2.7.1:
   version "2.10.0"
   resolved "https://registry.npmjs.org/store2/-/store2-2.10.0.tgz#46b82bb91878daf1b0d56dec2f1d41e54d5103cf"