Move instance from module to global scope

.gitignore

@@ -37,3 +37,7 @@ jspm_packages
 .node_repl_history
 
 *.tgz
+
+# This is a local copy of the express-http-context library
+# It is used to avoid a circular dependency on the express-http-context library
+packages/express-http-context-intermediate-library/express-http-context.js

index.js

@@ -1,10 +1,16 @@
 'use strict';
 
 const { AsyncLocalStorage } = require('async_hooks');
-const asyncLocalStorage = new AsyncLocalStorage();
+
+const STORAGE_KEY = Symbol.for(
+	'skonves/express-http-context/asyncLocalStorage',
+);
+
+globalThis[STORAGE_KEY] = globalThis[STORAGE_KEY] ?? new AsyncLocalStorage();
 
 /** Express.js middleware that is responsible for initializing the context for each request. */
 function middleware(req, res, next) {
+  const asyncLocalStorage = globalThis[STORAGE_KEY];
   if (!asyncLocalStorage.getStore()) {
     asyncLocalStorage.run(new Map(), () => next());
   } else {
@@ -17,7 +23,7 @@ function middleware(req, res, next) {
  * @param {string} key
  */
 function get(key) {
-	return asyncLocalStorage.getStore()?.get(key);
+	return globalThis[STORAGE_KEY].getStore()?.get(key);
 }
 
 /**
@@ -26,6 +32,7 @@ function get(key) {
  * @param {*} value
  */
 function set(key, value) {
+  const asyncLocalStorage = globalThis[STORAGE_KEY];
 	if (asyncLocalStorage.getStore()) {
 		asyncLocalStorage.getStore()?.set(key, value);
 		return value;
@@ -37,5 +44,5 @@ module.exports = {
 	middleware,
 	get: get,
 	set: set,
-	asyncLocalStorage
+	asyncLocalStorage: globalThis[STORAGE_KEY],
 };

jest.config.js

@@ -7,6 +7,7 @@ module.exports = {
     '!**/*.config.js',
     '!**/coverage/**',
     '!**/node_modules/**',
+    '!**/packages/**',
     '!**/tests/**',
   ],
   coverageDirectory: 'coverage',

package.json

@@ -4,10 +4,12 @@
   "description": "Get and set request-scoped context anywhere",
   "main": "index.js",
   "browser": "browser.js",
+  "sideEffects": true,
   "engines": {
     "node": ">=14.8.0"
   },
   "scripts": {
+    "pretest": "cp index.js packages/express-http-context-intermediate-library/express-http-context.js",
     "test": "jest"
   },
   "repository": {
@@ -32,6 +34,7 @@
   "homepage": "https://github.com/skonves/express-http-context#readme",
   "funding": "https://github.com/skonves/express-http-context?sponsor=1",
   "devDependencies": {
+    "@oliverlockwood/express-http-context-intermediate-library": "file:packages/express-http-context-intermediate-library",
     "express": "^4.21.2",
     "jest": "^29.7.0",
     "supertest": "^7.0.0"

packages/express-http-context-intermediate-library/README.md

@@ -0,0 +1,8 @@
+# express-http-context-intermediate-library
+
+An intermediate library, which makes use of express-http-context, to demonstrate existence (or otherwise!) of a bug
+
+
+### Publishing to NPM
+
+Run `./npmPublish.sh a.b.c`, where `a.b.c` is the intended semantic version (e.g. `1.2.3`).

packages/express-http-context-intermediate-library/index.js

@@ -0,0 +1,29 @@
+"use strict";
+
+const httpContext = require("./express-http-context");
+const { nanoid } = require("nanoid");
+
+const REQUEST_ID_HTTP_HEADER_NAME = "my-request-id";
+const REQUEST_ID_CONTEXT_KEY = "myRequestId";
+
+// less realistic, but useful for testing!
+const REQUEST_ID_IN_RESPONSE_HTTP_HEADER_NAME = "my-request-id-in-response";
+
+function init(app) {
+  app.use(httpContext.middleware);
+
+  app.use((req, res, next) => {
+    const requestId = req.header(REQUEST_ID_HTTP_HEADER_NAME) || nanoid();
+
+    httpContext.set(REQUEST_ID_CONTEXT_KEY, requestId);
+    res.header(REQUEST_ID_IN_RESPONSE_HTTP_HEADER_NAME, requestId);
+
+    next();
+  });
+}
+
+module.exports = {
+  init,
+  REQUEST_ID_CONTEXT_KEY,
+  REQUEST_ID_IN_RESPONSE_HTTP_HEADER_NAME,
+};

packages/express-http-context-intermediate-library/package.json

@@ -0,0 +1,36 @@
+{
+  "name": "@oliverlockwood/express-http-context-intermediate-library",
+  "version": "0.0.5-original-library",
+  "description": "An intermediate library, which makes use of express-http-context, to demonstrate existence (or otherwise!) of a bug",
+  "main": "index.js",
+  "types": "index.d.ts",
+  "engines": {
+    "node": ">=16.0.0"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/oliverlockwood/express-http-context-intermediate-library.git"
+  },
+  "keywords": [
+    "express",
+    "http",
+    "request",
+    "context"
+  ],
+  "author": "Oliver Lockwood",
+  "contributors": [
+    "Oliver Lockwood (@oliverlockwood)"
+  ],
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/oliverlockwood/express-http-context-intermediate-library/issues"
+  },
+  "homepage": "https://github.com/oliverlockwood/express-http-context-intermediate-library#readme",
+  "directories": {
+    "test": "test"
+  },
+  "dependencies": {
+    "express": "4.21.2",
+    "nanoid": "3.3.11"
+  }
+}

tests/express-test-harness.js

@@ -4,6 +4,7 @@ const express = require('express');
 const supertest = require('supertest');
 
 const httpContext = require('../index');
+const { init, REQUEST_ID_CONTEXT_KEY, REQUEST_ID_IN_RESPONSE_HTTP_HEADER_NAME } = require('@oliverlockwood/express-http-context-intermediate-library');
 
 describe('express-http-context', function () {
 	it('does not store or return context outside of request', function () {
@@ -222,4 +223,47 @@ describe('express-http-context', function () {
 			done();
 		});
 	});
+
+	it('maintains unique value when the library is depended upon both directly and transitively', async () => {
+		// ARRANGE
+		const app = express();
+
+		// this function in the test library makes the following two calls:
+		//   1.  app.use(middleware) and
+		//   2.  httpContext.set(REQUEST_ID_CONTEXT_KEY, <a unique id>)
+		// as can be seen in https://github.com/oliverlockwood/express-http-context-intermediate-library/blob/original-express-http-context/src/index.ts#L13-L19
+		init(app);
+
+		app.get('/', ((req, res) => {
+			httpContext.set('value', req.query['value']);
+
+			res.status(200).json({
+				fred: '123',
+				value: req.query['value'],
+				valueFromContext: httpContext.get('value'),
+				requestId: httpContext.get(REQUEST_ID_CONTEXT_KEY)
+			});
+		}));
+
+		const request = supertest(app);
+
+		// ACT
+		const [response1, response2] = await Promise.all([
+			request.get('/').query({ value: 'value1' }),
+			request.get('/').query({ value: 'value2' }),
+		]);
+
+		// ASSERT
+		expect(response1.body.value).toBe('value1');
+		expect(response2.body.value).toBe('value2');
+
+		expect(response1.header[REQUEST_ID_IN_RESPONSE_HTTP_HEADER_NAME]?.length).toBe(21);
+		expect(response2.header[REQUEST_ID_IN_RESPONSE_HTTP_HEADER_NAME]?.length).toBe(21);
+
+		expect(response1.body.requestId).toBe(response1.header[REQUEST_ID_IN_RESPONSE_HTTP_HEADER_NAME]);
+		expect(response2.body.requestId).toBe(response2.header[REQUEST_ID_IN_RESPONSE_HTTP_HEADER_NAME]);
+
+		expect(response1.body.valueFromContext).toBe('value1');
+		expect(response2.body.valueFromContext).toBe('value2');
+	});
 });