fix(fetch-adapter): set correct Content-Type for Node FormData (#6998)

emiedonmokumo · Copilot · jasonsaayman · web-flow · commit a9f47afbf322 · 2025-08-25T20:46:53.000+02:00
* fix(fetch-adapter): set correct Content-Type for Node FormData

* Update lib/helpers/resolveConfig.js

Co-authored-by: Copilot &lt;175728472+Copilot@users.noreply.github.com&gt;

* test(fetch): replace chai expect with Node assert

* fix: define formHeaders for FormData to resolve no-undef error

* fix: filter headers to only update the target headers

Co-authored-by: Copilot &lt;175728472+Copilot@users.noreply.github.com&gt;

---------

Co-authored-by: Copilot &lt;175728472+Copilot@users.noreply.github.com&gt;
Co-authored-by: Jay &lt;jasonsaayman@gmail.com&gt;
diff --git a/lib/helpers/resolveConfig.js b/lib/helpers/resolveConfig.js
@@ -10,7 +10,7 @@ import buildURL from "./buildURL.js";
 export default (config) => {
   const newConfig = mergeConfig({}, config);
 
-  let {data, withXSRFToken, xsrfHeaderName, xsrfCookieName, headers, auth} = newConfig;
+  let { data, withXSRFToken, xsrfHeaderName, xsrfCookieName, headers, auth } = newConfig;
 
   newConfig.headers = headers = AxiosHeaders.from(headers);
 
@@ -23,17 +23,21 @@ export default (config) => {
     );
   }
 
-  let contentType;
-
   if (utils.isFormData(data)) {
     if (platform.hasStandardBrowserEnv || platform.hasStandardBrowserWebWorkerEnv) {
-      headers.setContentType(undefined); // Let the browser set it
-    } else if ((contentType = headers.getContentType()) !== false) {
-      // fix semicolon duplication issue for ReactNative FormData implementation
-      const [type, ...tokens] = contentType ? contentType.split(';').map(token => token.trim()).filter(Boolean) : [];
-      headers.setContentType([type || 'multipart/form-data', ...tokens].join('; '));
+      headers.setContentType(undefined); // browser handles it
+    } else if (utils.isFunction(data.getHeaders)) {
+      // Node.js FormData (like form-data package)
+      const formHeaders = data.getHeaders();
+      // Only set safe headers to avoid overwriting security headers
+      const allowedHeaders = ['content-type', 'content-length'];
+      Object.entries(formHeaders).forEach(([key, val]) => {
+        if (allowedHeaders.includes(key.toLowerCase())) {
+          headers.set(key, val);
+        }
+      });
     }
-  }
+  }  
 
   // Add xsrf header
   // This is only done if running in a standard browser environment.
diff --git a/test/unit/adapters/fetch.js b/test/unit/adapters/fetch.js
@@ -10,7 +10,7 @@ import {
 } from '../../helpers/server.js';
 import axios from '../../../index.js';
 import stream from "stream";
-import {AbortController} from "abortcontroller-polyfill/dist/cjs-ponyfill.js";
+import { AbortController } from "abortcontroller-polyfill/dist/cjs-ponyfill.js";
 import util from "util";
 
 const pipelineAsync = util.promisify(stream.pipeline);
@@ -41,7 +41,7 @@ describe('supports fetch with nodejs', function () {
 
       server = await startHTTPServer((req, res) => res.end(originalData));
 
-      const {data} = await fetchAxios.get('/', {
+      const { data } = await fetchAxios.get('/', {
         responseType: 'text'
       });
 
@@ -53,7 +53,7 @@ describe('supports fetch with nodejs', function () {
 
       server = await startHTTPServer((req, res) => res.end(originalData));
 
-      const {data} = await fetchAxios.get('/', {
+      const { data } = await fetchAxios.get('/', {
         responseType: 'arraybuffer'
       });
 
@@ -65,7 +65,7 @@ describe('supports fetch with nodejs', function () {
 
       server = await startHTTPServer((req, res) => res.end(originalData));
 
-      const {data} = await fetchAxios.get('/', {
+      const { data } = await fetchAxios.get('/', {
         responseType: 'blob'
       });
 
@@ -77,7 +77,7 @@ describe('supports fetch with nodejs', function () {
 
       server = await startHTTPServer((req, res) => res.end(originalData));
 
-      const {data} = await fetchAxios.get('/', {
+      const { data } = await fetchAxios.get('/', {
         responseType: 'stream'
       });
 
@@ -104,7 +104,7 @@ describe('supports fetch with nodejs', function () {
         res.end(await response.text());
       });
 
-      const {data} = await fetchAxios.get('/', {
+      const { data } = await fetchAxios.get('/', {
         responseType: 'formdata'
       });
 
@@ -114,11 +114,11 @@ describe('supports fetch with nodejs', function () {
     });
 
     it(`should support json response type`, async () => {
-      const originalData = {x: 'my data'};
+      const originalData = { x: 'my data' };
 
       server = await startHTTPServer((req, res) => res.end(JSON.stringify(originalData)));
 
-      const {data} = await fetchAxios.get('/', {
+      const { data } = await fetchAxios.get('/', {
         responseType: 'json'
       });
 
@@ -153,8 +153,8 @@ describe('supports fetch with nodejs', function () {
 
         const samples = [];
 
-        const {data} = await fetchAxios.post('/', readable, {
-          onUploadProgress: ({loaded, total, progress, bytes, upload}) => {
+        const { data } = await fetchAxios.post('/', readable, {
+          onUploadProgress: ({ loaded, total, progress, bytes, upload }) => {
             console.log(`Upload Progress ${loaded} from ${total} bytes (${(progress * 100).toFixed(1)}%)`);
 
             samples.push({
@@ -188,10 +188,10 @@ describe('supports fetch with nodejs', function () {
         }()));
       });
 
-      it('should not fail with get method', async() => {
+      it('should not fail with get method', async () => {
         server = await startHTTPServer((req, res) => res.end('OK'));
 
-        const {data} = await fetchAxios.get('/', {
+        const { data } = await fetchAxios.get('/', {
           onUploadProgress() {
 
           }
@@ -227,8 +227,8 @@ describe('supports fetch with nodejs', function () {
 
         const samples = [];
 
-        const {data} = await fetchAxios.post('/', readable, {
-          onDownloadProgress: ({loaded, total, progress, bytes, download}) => {
+        const { data } = await fetchAxios.post('/', readable, {
+          onDownloadProgress: ({ loaded, total, progress, bytes, download }) => {
             console.log(`Download Progress ${loaded} from ${total} bytes (${(progress * 100).toFixed(1)}%)`);
 
             samples.push({
@@ -269,8 +269,8 @@ describe('supports fetch with nodejs', function () {
     server = await startHTTPServer((req, res) => res.end(req.headers.authorization));
 
     const user = 'foo';
-    const headers = {Authorization: 'Bearer 1234'};
-    const res = await axios.get('http://' + user + '@localhost:4444/', {headers: headers});
+    const headers = { Authorization: 'Bearer 1234' };
+    const res = await axios.get('http://' + user + '@localhost:4444/', { headers: headers });
 
     const base64 = Buffer.from(user + ':', 'utf8').toString('base64');
     assert.equal(res.data, 'Basic ' + base64);
@@ -279,12 +279,12 @@ describe('supports fetch with nodejs', function () {
   it("should support stream.Readable as a payload", async () => {
     server = await startHTTPServer();
 
-    const {data} = await fetchAxios.post('/', stream.Readable.from('OK'));
+    const { data } = await fetchAxios.post('/', stream.Readable.from('OK'));
 
     assert.strictEqual(data, 'OK');
   });
 
-  describe('request aborting', function() {
+  describe('request aborting', function () {
     it('should be able to abort the request stream', async function () {
       server = await startHTTPServer({
         rate: 100000,
@@ -316,7 +316,7 @@ describe('supports fetch with nodejs', function () {
         controller.abort(new Error('test'));
       }, 800);
 
-      const {data} = await fetchAxios.get('/', {
+      const { data } = await fetchAxios.get('/', {
         responseType: 'stream',
         signal: controller.signal
       });
@@ -328,7 +328,7 @@ describe('supports fetch with nodejs', function () {
   });
 
   it('should support a timeout', async () => {
-    server = await startHTTPServer(async(req, res) => {
+    server = await startHTTPServer(async (req, res) => {
       await setTimeoutAsync(1000);
       res.end('OK');
     });
@@ -337,7 +337,7 @@ describe('supports fetch with nodejs', function () {
 
     const ts = Date.now();
 
-    await assert.rejects(async() => {
+    await assert.rejects(async () => {
       await fetchAxios('/', {
         timeout
       })
@@ -358,10 +358,10 @@ describe('supports fetch with nodejs', function () {
     assert.equal(res.config.url, '/foo');
   });
 
-  it('should support params', async() => {
+  it('should support params', async () => {
     server = await startHTTPServer((req, res) => res.end(req.url));
 
-    const {data} = await fetchAxios.get('/?test=1', {
+    const { data } = await fetchAxios.get('/?test=1', {
       params: {
         foo: 1,
         bar: 2
@@ -372,7 +372,7 @@ describe('supports fetch with nodejs', function () {
   });
 
   it('should handle fetch failed error as an AxiosError with ERR_NETWORK code', async () => {
-    try{
+    try {
       await fetchAxios('http://notExistsUrl.in.nowhere');
       assert.fail('should fail');
     } catch (err) {
@@ -387,10 +387,26 @@ describe('supports fetch with nodejs', function () {
       res.end(req.url)
     });
 
-    const {headers} = await fetchAxios.get('/', {
+    const { headers } = await fetchAxios.get('/', {
       responseType: 'stream'
     });
 
     assert.strictEqual(headers.get('foo'), 'bar');
   });
-});
+
+  describe('fetch adapter - Content-Type handling', function () {
+    it('should set correct Content-Type for FormData automatically', async function () {
+      const FormData = (await import('form-data')).default; // Node FormData
+      const form = new FormData();
+      form.append('foo', 'bar');
+  
+      server = await startHTTPServer((req, res) => {
+        const contentType = req.headers['content-type'];
+        assert.match(contentType, /^multipart\/form-data; boundary=/i);
+        res.end('OK');
+      });
+  
+      await fetchAxios.post('/form', form);
+    });
+  });  
+});
