fix: allow to reuse config (e.g. axios-retry) (#650)

* add test for reusing config

* fix: allow to reuse config (e.g. axios-retry)

* closes #602
* closes #609

* docs: update README

README.md

@@ -51,6 +51,13 @@ declare module 'axios' {
 
 See also https://github.com/axios/axios#request-config .
 
+## FAQ
+
+- Q. Why can't I assign the httpAgent / httpsAgent?
+  - A. axios-cookiejar-support uses httpAgent / httpsAgent to read and write cookies. If other Agents are assigned, cookies cannot be read/written.
+- Q. I want to use it with another Agent (e.g., http-proxy-agent).
+  - A. Consider using http-cookie-agent. axios-cookiejar-support also uses http-cookie-agent. Read http-cookie-agent's README for more details.
+
 ## Contributing
 
 PRs accepted.

src/__tests__/basic.spec.ts

@@ -215,3 +215,20 @@ test.serial('should throw error when config.jar was assigned with boolean', asyn
   t.plan(1);
   server.close();
 });
+
+test.serial('should allow to reuse config', async (t) => {
+  const { port } = await createTestServer([
+    (_req, res) => {
+      res.end('Hello World!');
+    },
+    (_req, res) => {
+      res.end('Hello World!');
+    },
+  ]);
+
+  const jar = new CookieJar();
+
+  const { config } = await axios.get(`http://localhost:${port}`, { jar, responseType: 'text' });
+  await axios.get(`http://localhost:${port}`, config);
+  t.pass();
+});

src/index.ts

@@ -2,6 +2,8 @@ import type { AxiosInstance, AxiosRequestConfig, AxiosStatic } from 'axios';
 import { HttpCookieAgent, HttpsCookieAgent } from 'http-cookie-agent/http';
 import type { CookieJar } from 'tough-cookie';
 
+const AGENT_CREATED_BY_AXIOS_COOKIEJAR_SUPPORT = Symbol('AGENT_CREATED_BY_AXIOS_COOKIEJAR_SUPPORT');
+
 declare module 'axios' {
   interface AxiosRequestConfig {
     jar?: CookieJar;
@@ -18,12 +20,28 @@ function requestInterceptor(config: AxiosRequestConfig): AxiosRequestConfig {
     throw new Error('config.jar does not accept boolean since axios-cookiejar-support@2.0.0.');
   }
 
-  if (config.httpAgent || config.httpsAgent) {
+  if (
+    (config.httpAgent != null && config.httpAgent[AGENT_CREATED_BY_AXIOS_COOKIEJAR_SUPPORT] !== true) ||
+    (config.httpsAgent != null && config.httpsAgent[AGENT_CREATED_BY_AXIOS_COOKIEJAR_SUPPORT] !== true)
+  ) {
     throw new Error('axios-cookiejar-support does not support for use with other http(s).Agent.');
   }
 
   config.httpAgent = new HttpCookieAgent({ cookies: { jar: config.jar } });
+  Object.defineProperty(config.httpAgent, AGENT_CREATED_BY_AXIOS_COOKIEJAR_SUPPORT, {
+    configurable: false,
+    enumerable: false,
+    value: true,
+    writable: false,
+  });
+
   config.httpsAgent = new HttpsCookieAgent({ cookies: { jar: config.jar } });
+  Object.defineProperty(config.httpsAgent, AGENT_CREATED_BY_AXIOS_COOKIEJAR_SUPPORT, {
+    configurable: false,
+    enumerable: false,
+    value: true,
+    writable: false,
+  });
 
   return config;
 }