chore: Ensure to install all nested packages on npm install

package.json

@@ -5,6 +5,7 @@
   "license": "Apache",
   "scripts": {
     "lint": "eslint --ignore-path .gitignore .",
+    "postinstall": "./scripts/install-nested-packages.js",
     "prettier-check": "prettier -c --ignore-path .gitignore \"**/*.{css,html,js,json,yaml,yml}\"",
     "prettify": "prettier --write --ignore-path .gitignore \"**/*.{css,html,js,json,yaml,yml}\"",
     "test": "jest --bail 1 --testEnvironment node ./test/integration.test.js"

scripts/install-nested-packages.js

@@ -0,0 +1,39 @@
+#!/usr/bin/env node
+
+'use strict';
+
+process.on('unhandledRejection', (reason) => {
+  throw reason;
+});
+
+const path = require('path');
+const childProcess = require('child_process');
+
+const platformRoot = path.resolve(__dirname, '..');
+
+const npmInstall = (packagePath) =>
+  new Promise((resolve, reject) => {
+    console.log('---------------------------------------');
+    console.log(`Install \x1b[33m${packagePath}\x1b[39m ...\n`);
+    const child = childProcess.spawn('npm', ['install'], {
+      cwd: path.resolve(platformRoot, packagePath),
+      stdio: 'inherit',
+    });
+    child.on('error', reject);
+    child.on('close', (code) => {
+      if (code) {
+        reject(new Error(`npm install failed at ${packagePath}`));
+      } else {
+        resolve();
+      }
+    });
+  });
+
+const packagesPaths = ['src', 'src/_express', 'src/_src', 'test/src'];
+
+(async () => {
+  // Running multiple "npm install" prcesses in parallel is not confirmed to be safe.
+  for (const packagePath of packagesPaths) {
+    await npmInstall(packagePath);
+  }
+})();