fetch-mock Response.body is not always a stream in Node.js

[fluggo]

WhatWG fetch API spec requires that Body.body is of type ReadableStream. node-fetch interprets the standard as requiring a Node.js Readable stream. fetch-mock returns a Buffer if anything other than a Readable is given to the Response object.

In Node:

const fetchMock = require('fetch-mock');
const fetch = fetchMock.sandbox();

fetch.get('http://www.www.com.com', 'woo woo woo');

fetch('http://www.www.com.com').then(resp => resp.body.pipe(process.stdout));

...causes:

(node:36650) UnhandledPromiseRejectionWarning: TypeError: resp.body.pipe is not a function
    at /Users/fluggo/software/fetchmocktest/test-stream.js:6:56

This appears to be a bug in the ResponseBuilder, I have a patch.

[fluggo]

Workaround:

const stream = require('stream');
const _baseResponseBuilder = require('fetch-mock/cjs/lib/response-builder');

require.cache[require.resolve('fetch-mock/cjs/lib/response-builder')] = {
  ..._baseResponseBuilder,
  exports: (options) => _baseResponseBuilder({ ...options, Stream: stream }),
};

const nodeFetch = require('node-fetch');
// and so forth

[jimmywarting]

in node-fetch@v3 the res.body is normalized into a node readable stream or null

[wheresrhys]

Should not be a problem any more in fetch-mock@10