overwrite/delete headers from axios.create instance

Hi there, is the follow behavior a bug or not intend:

if i create a axios instance with a header like this

const HTTP = axios.create({
  baseURL: 'test.test',
  headers: {
    'X-Foo': 'value',
  },
});

it is no longer possible to overwrite/delete the header like

HTTP({ url: 'other', baseURL: null, headers: null })

baseUrl and url can be overwritten, headers not. why. respectively how i can?

Environment:

• Axios Version latest

❤️ axios

[jasonsaayman]

@webdesignberlin this is due to parameters now being deep merged, though I do like the idea of being able to overwrite the whole headers object in one go. There is actually no workaround, you could set the property headers.X-Foo to null. However, once the header has been added to the instance it seems to not be possible to clear it completely. I will see if there is a way to have both deep merge as well as a way to completely clear the headers.

[chinesedfan]

@webdesignberlin Do you confirm that case3 works for you? I tested with following script,

var axios = require('axios')
var adapter = function(config) {
  console.log(config.headers)
  return Promise.resolve({data: 12})
}

// set the log adapter
axios(({url:'/api', baseURL:null,headers:null, adapter}))
axios.post('/api', { content1: 'blubb1', content2: 'blubb2', }, { headers: null, adapter })
axios({ url: '/api', method: 'post', headers: null, data: { content1: 'blubb1', content2: 'blubb2', }, adapter})

Both v0.19.0 and v0.21.1 have the same output. The config merging is working as expected. The reason why post method will still have headers is due to the default transformRequest adds for object data.

{}
{ 'Content-Type': 'application/json;charset=utf-8' }
{ 'Content-Type': 'application/json;charset=utf-8' }