Fix/form data in response

src/body.js

@@ -61,6 +61,7 @@ export default class Body {
 		}
 
 		this[INTERNALS] = {
+			/** @type {Stream|Buffer|Blob|null} */
 			body,
 			boundary,
 			disturbed: false,
@@ -197,14 +198,15 @@ async function consumeBody(data) {
 
 	try {
 		for await (const chunk of body) {
-			if (data.size > 0 && accumBytes + chunk.length > data.size) {
+			const bytes = typeof chunk === 'string' ? Buffer.from(chunk) : chunk;
+			if (data.size > 0 && accumBytes + bytes.byteLength > data.size) {
 				const err = new FetchError(`content size at ${data.url} over limit: ${data.size}`, 'max-size');
 				body.destroy(err);
 				throw err;
 			}
 
-			accumBytes += chunk.length;
-			accum.push(chunk);
+			accumBytes += bytes.byteLength;
+			accum.push(bytes);
 		}
 	} catch (error) {
 		if (error instanceof FetchBaseError) {
@@ -217,10 +219,6 @@ async function consumeBody(data) {
 
 	if (body.readableEnded === true || body._readableState.ended === true) {
 		try {
-			if (accum.every(c => typeof c === 'string')) {
-				return Buffer.from(accum.join(''));
-			}
-
 			return Buffer.concat(accum, accumBytes);
 		} catch (error) {
 			throw new FetchError(`Could not create Buffer from response body for ${data.url}: ${error.message}`, 'system', error);
@@ -323,7 +321,7 @@ export const extractContentType = (body, request) => {
  *
  * ref: https://fetch.spec.whatwg.org/#concept-body-total-bytes
  *
- * @param {any} obj.body Body object from the Body instance.
+ * @param {Body} request Body object from the Body instance.
  * @returns {number | null}
  */
 export const getTotalBytes = request => {

src/response.js

@@ -25,7 +25,7 @@ export default class Response extends Body {
 		const headers = new Headers(options.headers);
 
 		if (body !== null && !headers.has('Content-Type')) {
-			const contentType = extractContentType(body);
+			const contentType = extractContentType(body, this);
 			if (contentType) {
 				headers.append('Content-Type', contentType);
 			}

src/utils/is.js

@@ -11,7 +11,7 @@ const NAME = Symbol.toStringTag;
  * ref: https://github.com/node-fetch/node-fetch/issues/296#issuecomment-307598143
  *
  * @param  {*} obj
- * @return {boolean}
+ * @return {object is URLSearchParams}
  */
 export const isURLSearchParameters = object => {
 	return (
@@ -31,7 +31,7 @@ export const isURLSearchParameters = object => {
  * Check if `object` is a W3C `Blob` object (which `File` inherits from)
  *
  * @param  {*} obj
- * @return {boolean}
+ * @return {object is Blob}
  */
 export const isBlob = object => {
 	return (
@@ -48,7 +48,7 @@ export const isBlob = object => {
  * Check if `obj` is a spec-compliant `FormData` object
  *
  * @param {*} object
- * @return {boolean}
+ * @return {object is FormData}
  */
 export function isFormData(object) {
 	return (
@@ -70,7 +70,7 @@ export function isFormData(object) {
  * Check if `obj` is an instance of AbortSignal.
  *
  * @param  {*} obj
- * @return {boolean}
+ * @return {object is AbortSignal}
  */
 export const isAbortSignal = object => {
 	return (

test/form-data.js

@@ -1,5 +1,7 @@
 import FormData from 'formdata-node';
 import Blob from 'fetch-blob';
+import {Response, Request} from '../src/index.js';
+import {getTotalBytes} from '../src/body.js';
 
 import chai from 'chai';
 
@@ -101,4 +103,30 @@ describe('FormData', () => {
 
 		expect(String(await read(formDataIterator(form, boundary)))).to.be.equal(expected);
 	});
+
+	it('Response supports FormData body', async () => {
+		const form = new FormData();
+		form.set('blob', new Blob(['Hello, World!'], {type: 'text/plain'}));
+
+		const response = new Response(form);
+		const type = response.headers.get('content-type') || '';
+		expect(type).to.match(/multipart\/form-data;\s*boundary=/);
+		expect(await response.text()).to.have.string('Hello, World!');
+		// Note: getTotalBytes assumes body could be form data but it never is
+		// because it gets normalized into a stream.
+		expect(getTotalBytes({...response, body: form})).to.be.greaterThan(20);
+	});
+
+	it('Request supports FormData body', async () => {
+		const form = new FormData();
+		form.set('blob', new Blob(['Hello, World!'], {type: 'text/plain'}));
+
+		const request = new Request('https://github.com/node-fetch/', {
+			body: form,
+			method: 'POST'
+		});
+		const type = request.headers.get('content-type') || '';
+		expect(type).to.match(/multipart\/form-data;\s*boundary=/);
+		expect(await request.text()).to.have.string('Hello, World!');
+	});
 });