Use the proper transformers for specific dataType and responseType values.

[rubennorte]

Implement and document proper transformation of request and response body according to dataType and responseType options.

This will fix: #375, #448, #765, #793

[ClementParis016]

Maybe also #724 and #907

[codeclown]

I think there are two sides to this, right?

1. Fixing the behaviour when responseType: 'text' should be considered an essential bugfix which addresses a bug in current behaviour.
2. Implementing dataType would be a new feature, and it also is confusing because currently the automatic type detection of request body is quite nice and works.

The landscape for fixing the responseType bug is quite hazardous:

• This test asserts that a response containing a valid JSON string (and content-type header) is parsed as JSON automatically, regardless of responseType:

axios/test/unit/adapters/http.js

Line 53 in ec97c68

testJSON: function (test) {

• This test asserts that also in case of failure (non-2xx response), if the response contains a valid JSON string (even without content-type header), it is parsed automatically:

axios/test/specs/requests.spec.js

Line 161 in ec97c68

it('should return JSON when rejecting', function (done) {

Both of these stem from the fact that response parsing has defaulted to always trying to parse JSON , regardless of responseType or headers['content-type'].

[ClementParis016]

Then, if we want to keep the default parsing behavior a possible solution could be to add an option to disable automatic parsing?

[chinesedfan]

Here are my conclusions,

• Most users complained that the response is parsed as json, even thought responseType: text has been set. when response type is text and accept is text but response is json format, it will be json. #375, "responseType" param is unavailable #765, responseType: 'text' return Json Object #907
• And consider if the JSON is failed to be parsed, How to handle error from JSON.parse #61
• Clarity in document that how the default responseType: json is achieved. No default value for responseType config option #724
• Mention situations to set as blob or arraybuffer or other values. Maybe a link to the original responseType. Missing documentation for downloading binary files #448, Infer responseType from response headers? #793

[Scriptim]

axios/lib/defaults.js

Lines 57 to 65 in 6642ca9

	transformResponse: [function transformResponse(data) {
	/*eslint no-param-reassign:0*/
	if (typeof data === 'string') {
	try {
	data = JSON.parse(data);
	} catch (e) { /* Ignore */ }
	}
	return data;
	}],

I really don't think that the current default parsing behavior is sensible.

It may even cause the data to be altered under certain circumstances, e. g.:
Let's say a server sends a 16 character string (with according header) of digits: 4201172030730738. The default behavior would convert this to the integer value 4201172030730738, although this is obviously not a JSON object (even if it is a valid JSON value). In case the string is e.g. 9100000000000001 (i.e. > Number.MAX_SAFE_INTEGER), parsing will cause the value to be changed to 9100000000000000 due to inaccuracy of the float data type.

This is not a far-fetched example, but rather a problem that has really occurred and has required quite a bit of debugging. Especially since this is not adequately documented in my opinion.

I suggest that parsing to JSON is only done if the data is really in JSON format, i. e. the Content-Type header is set to application/json and/or the value of dataType/responseType is set accordingly.

[scudette]

Jut hit this bug as well but I did find a workaround which seems to work for me so might save someone else some time:

axios({
        responseType: 'blob',
        method: 'get',
        url: url,
        params: params,
 }).then((response) => response.data.text()};

[lichader]

I also got this bug and if you are using the alias methods, you can always override the default transformer:

const axiosResponse = await this.httpClient.get(
    `url`,
    {
        transformResponse: (data) => {
            return data;
        },
    }
);

[lucrus73]

FYI I've just replaced Axois with Got because of this.

[jasonsaayman]

Default parsing has been changed, please open a new issue should this still be a issue.

[gerarts]

Ran into this on 0.24.0. Thanks @lucrus73 , Got works great!

[landsman]

I had a problem with using axios to file download, where I want to setup responseType: 'arraybuffer'.
In case of error response I was receiving JSON response from the server, but axios was doing conversion to arraybuffer as well in the catch block.

So I have to convert the arraybuffer response to json by this:

const data = await JSON.parse(new TextDecoder().decode(error.response.data));

For people facing the same issue...