#1395 breaks custom config

Summary

#1395 launched a fix that instance config may override global config, but it ignore custom configs. So it will break something we’d like to attach into the config and access in interceptor (e.g. CookieJar).

For example (https://codepen.io/anon/pen/gjZRdR?editors=1111):

const inst = axios.create();
inst.interceptors.request.use(config => {
  console.log('should be "test", actual', config.testAttr);
})
inst.get('/', {
  testAttr: 'test',
});

Context

• axios version: v0.19.0-beta.1
• Environment: node & chrome

[ustbhuangyi]

I am looking forward to this feature😀

[edgesite]

@zcei Great point. Can we just make config.userData: any to store user data. But since it’s a regression, we still need to fix it or put it into breaking changes since it will break some old codes.