fix: Update FetchHttpClient to send empty string for empty POST/PUT/PATCH requests.

lib/net/FetchHttpClient.js

@@ -39,11 +39,19 @@ class FetchHttpClient extends HttpClient {
     );
     url.port = port;
 
+    // For methods which expect payloads, we should always pass a body value
+    // even when it is empty. Without this, some JS runtimes (eg. Deno) will
+    // inject a second Content-Length header. See https://github.com/stripe/stripe-node/issues/1519
+    // for more details.
+    const methodHasPayload =
+      method == 'POST' || method == 'PUT' || method == 'PATCH';
+    const body = requestData || (methodHasPayload ? '' : undefined);
+
     const fetchFn = this._fetchFn || fetch;
     const fetchPromise = fetchFn(url.toString(), {
       method,
       headers,
-      body: requestData || undefined,
+      body,
     });
 
     // The Fetch API does not support passing in a timeout natively, so a

test/net/FetchHttpClient.spec.js

@@ -2,6 +2,7 @@
 
 const expect = require('chai').expect;
 const fetch = require('node-fetch');
+const nock = require('nock');
 const {Readable} = require('stream');
 const {FetchHttpClient} = require('../../lib/net/FetchHttpClient');
 
@@ -56,4 +57,58 @@ describe('FetchHttpClient', () => {
       });
     });
   });
+
+  describe('it sets a body value for empty POST requests', () => {
+    let capturedBody;
+
+    const patchedFetch = (url, params) => {
+      capturedBody = params.body;
+      return fetch(url, params);
+    };
+
+    nock('http://stripe.com')
+      .post('/test', '')
+      .reply(200);
+
+    const client = new FetchHttpClient(patchedFetch);
+    client.makeRequest(
+      'stripe.com',
+      80,
+      '/test',
+      'POST',
+      {},
+      '', // requestData
+      'http',
+      1000
+    );
+
+    expect(capturedBody).to.equal('');
+  });
+
+  describe('it does not set a body value for empty GET requests', () => {
+    let capturedBody;
+
+    const patchedFetch = (url, params) => {
+      capturedBody = params.body;
+      return fetch(url, params);
+    };
+
+    nock('http://stripe.com')
+      .get('/test')
+      .reply(200);
+
+    const client = new FetchHttpClient(patchedFetch);
+    client.makeRequest(
+      'stripe.com',
+      80,
+      '/test',
+      'GET',
+      {},
+      '', // requestData
+      'http',
+      1000
+    );
+
+    expect(capturedBody).to.be.undefined;
+  });
 });