Set content-length automatically for fs.createReadStream

index.js

@@ -253,10 +253,14 @@ function requestAsEventEmitter(opts) {
 		try {
 			uploadBodySize = await getBodySize(opts);
 
+			// This is the second try at setting a `content-length` header.
+			// This supports getting the size async, in contrast to
+			// https://github.com/sindresorhus/got/blob/82763c8089596dcee5eaa7f57f5dbf8194842fe6/index.js#L579-L582
+			// TODO: We should unify these two at some point
 			if (
+				uploadBodySize > 0 &&
 				is.undefined(opts.headers['content-length']) &&
-				is.undefined(opts.headers['transfer-encoding']) &&
-				isFormData(opts.body)
+				is.undefined(opts.headers['transfer-encoding'])
 			) {
 				opts.headers['content-length'] = uploadBodySize;
 			}

readme.md

@@ -114,15 +114,15 @@ Returns a `Stream` instead of a `Promise`. This is equivalent to calling `got.st
 
 ###### body
 
-Type: `string` `Buffer` `stream.Readable`
+Type: `string` `Buffer` `stream.Readable` [`form-data` instance](https://github.com/form-data/form-data)
 
 *This is mutually exclusive with stream mode.*
 
 Body that will be sent with a `POST` request.
 
 If present in `options` and `options.method` is not set, `options.method` will be set to `POST`.
 
-If `content-length` or `transfer-encoding` is not set in `options.headers` and `body` is a string or buffer, `content-length` will be set to the body length.
+The `content-length` header will be automatically set if `body` is a `string` / `Buffer` / `fs.createReadStream` instance / [`form-data` instance](https://github.com/form-data/form-data), and `content-length` and `transfer-encoding` are not manually set in `options.headers`.
 
 ###### encoding
 

test/fixtures/stream-content-length

@@ -0,0 +1 @@
+Unicorns

test/headers.js

@@ -1,3 +1,5 @@
+import fs from 'fs';
+import path from 'path';
 import test from 'ava';
 import FormData from 'form-data';
 import got from '..';
@@ -115,6 +117,14 @@ test('form-data sets content-length', async t => {
 	t.is(headers['content-length'], '157');
 });
 
+test('stream as options.body sets content-length', async t => {
+	const {body} = await got(s.url, {
+		body: fs.createReadStream(path.join(__dirname, 'fixtures/stream-content-length'))
+	});
+	const headers = JSON.parse(body);
+	t.is(headers['content-length'], '9');
+});
+
 test('remove null value headers', async t => {
 	const {body} = await got(s.url, {
 		headers: {