Got RequestError when explicitly set responseType to undefined

[nguyenlc1993]

Describe the bug

• Node.js version: v12.16.2
• OS & version: Ubuntu 18.04

The project at my company uses got-fetch library, which uses got as peer dependency to create fetch-like function. Starting with got v11.1.1, we encounter this error when using got-fetch:

RequestError: Unknown body type 'undefined' in "https://www.google.com/" in "https://www.google.com/"
    at Object.exports.parseBody (/home/nguyen/Desktop/got-test/node_modules/got/dist/source/as-promise/core.js:29:15)
    at PromisableRequest.<anonymous> (/home/nguyen/Desktop/got-test/node_modules/got/dist/source/as-promise/index.js:78:44)
    at Object.exports.parseBody (/home/nguyen/Desktop/got-test/node_modules/got/dist/source/as-promise/core.js:23:15)
    at PromisableRequest.<anonymous> (/home/nguyen/Desktop/got-test/node_modules/got/dist/source/as-promise/index.js:78:44)
    at processTicksAndRejections (internal/process/task_queues.js:97:5)

After investigating the source code, we found that got-fetch sets responseType to be undefined and parses the response body by itself.

got-fetch/src/lib/fetch.ts:53

    const gotOpts: GotOptions = {
      // url needs to be stringified to support UNIX domain sockets, and
      // For more info see https://github.com/alexghr/got-fetch/pull/8
      url: url.toString(),
      searchParams,
      followRedirect: true,
      throwHttpErrors: false,
      method: (request.method as any) || 'get',
      isStream: false,
      resolveBodyOnly: false,
      // we'll do our own response parsing in `GotFetchResponse`
      responseType: undefined
    };

When we run test code with responseType explicitly set to undefined, we also got the same behavior. This behavior does not happen in got v11.1.0 and before.

Actual behavior

Got throws RequestError: Unknown body type 'undefined'.

Expected behavior

Got throws no error and return response as normal.

Code to reproduce

const got = require('got');

(async function() {
    const response = await got('https://www.google.com', {
        responseType: undefined,
    });
    console.log(response.body);
})();

Checklist

• I have read the documentation.
• I have tried my code with the latest version of Node.js and Got.

[Giotino]

According to the documentation responseType must be a string ('text', 'json' or 'buffer').

That behavior is due to this code:
https://github.com/sindresorhus/got/blob/9770e540d088c35ec0b467fa3d2fafb60ed6797d/source/as-promise/core.ts#L23,L42

[nguyenlc1993]

According to the documentation responseType must be a string ('text', 'json' or 'buffer').

That behavior is due to this code:
https://github.com/sindresorhus/got/blob/9770e540d088c35ec0b467fa3d2fafb60ed6797d/source/as-promise/core.ts#L23,L42

Thank you, I know that undefined is not a valid value for responseType, and also know the code that caused the behavior. I just don't understand why this behavior did not happen in earlier versions, as well as why responseType not default to text when set to undefined.
The issue caused us not be able to update got to latest version, so I wonder if the old behavior can be restored.

[Giotino]

I just don't understand why this behavior did not happen in earlier versions

In Got v10 there was this line after the merge (between default values and user options)

got/source/normalize-arguments.ts

Line 228 in 5c74084

options.responseType = options.responseType ?? 'text';

That took care of defaulting responseType to 'text' event if it was overwritten by the user options as undefined.

as well as why responseType not default to text when set to undefined.

This is because responseType , documentation wise, cannot be undefined.

I don't mean to be rude but you where using it wrong, even the Got v10 documentation states that it must be

Type: string

[szmarczak]

Options are optional, so when you pass anything as undefined it should not throw.