Content-type header for application/json should not contain charset field, according do RFC 8259

Describe the bug According to RFC 8259 - The JavaScript Object Notation (JSON) Data Interchange Format content-type application/json does not have any charset defined, as it must be utf-8 encoded. Older specifications allowed other unicode encodings, and parsers were detecting exact encoding used by first four bytes, still not by charset param.

Axios defaults to header Content-Type: application/json;charset=utf-8 for some types of sent data.

This breaks some HTTP servers and applications, who are not recognizing the content-type.

To Reproduce

axios.post("http://example.com", {an: "object"});
// Content-Type: application/json;charset=utf-8 header will be set

Expected behavior Content-Type: application/json header should be set as default for object data, without charset parameter.

Environment:

• Axios Version - 0.18.0, I’ve also checked master branch source - it is still there. https://github.com/axios/axios/blob/b4c5d35d2875191dfa8c3919d4227dce8e2ad23f/lib/defaults.js#L52

Additional context/Screenshots This breaks some parts of the rabbitmq-management API.

Related issues: https://github.com/axios/axios/issues/859

[OJezu]

@chinesedfan where in RFC7231 is charset parameter defined for application/json? It’s not, because parameter names are defined for concrete media-types in appropriate RFCs. charset parameter is neither declared for all headers nor for all media-types. application/json media-type does not have “charset” parameter defined.

From RFC7231

The presence or absence of a parameter might be significant to the processing of a media-type, depending on its definition within the media type registry.

See IANA media type registry for application/json: https://www.iana.org/assignments/media-types/application/json

And compare to plain/html entry which has charset parameter explicitly defined: https://www.iana.org/assignments/media-types/text/html

[jasonsaayman]

We should try mend this in 0.20.0 I will look at the pull request.