fix redirect interceptor with FormData body

lib/handler/redirect-handler.js

@@ -75,7 +75,8 @@ class RedirectHandler {
       this.opts.body &&
       typeof this.opts.body !== 'string' &&
       !ArrayBuffer.isView(this.opts.body) &&
-      util.isIterable(this.opts.body)
+      util.isIterable(this.opts.body) &&
+      !util.isFormDataLike(this.opts.body)
     ) {
       // TODO: Should we allow re-using iterable if !this.opts.idempotent
       // or through some other flag?

test/interceptors/redirect-issue-3803.js

@@ -0,0 +1,40 @@
+'use strict'
+
+const { FormData, request, Agent, interceptors } = require('../..')
+const { test } = require('node:test')
+const { createServer } = require('node:http')
+const { once } = require('node:events')
+const { tspl } = require('@matteo.collina/tspl')
+
+test('redirecting works with a FormData body', async (t) => {
+  const plan = tspl(t, { plan: 1 })
+
+  const server = createServer((req, res) => {
+    if (req.url === '/1') {
+      res.writeHead(302, undefined, { location: '/2' })
+      res.end()
+    } else {
+      res.end('OK')
+    }
+  }).listen(0)
+
+  t.after(() => server.close())
+  await once(server, 'listening')
+
+  const agent = new Agent().compose(interceptors.redirect({ maxRedirections: 1 }))
+
+  const body = new FormData()
+  body.append('hello', 'world')
+
+  const { context } = await request(`http://localhost:${server.address().port}/1`, {
+    body,
+    method: 'POST',
+    dispatcher: agent,
+    maxRedirections: 1
+  })
+
+  plan.deepStrictEqual(context.history, [
+    new URL(`http://localhost:${server.address().port}/1`),
+    new URL(`http://localhost:${server.address().port}/2`)
+  ])
+})

types/index.d.ts

@@ -40,7 +40,6 @@ declare namespace Undici {
   const RedirectHandler: typeof import ('./handlers').RedirectHandler
   const DecoratorHandler: typeof import ('./handlers').DecoratorHandler
   const RetryHandler: typeof import ('./retry-handler').default
-  const createRedirectInterceptor: typeof import ('./interceptors').default.createRedirectInterceptor
   const BalancedPool: typeof import('./balanced-pool').default
   const Client: typeof import('./client').default
   const buildConnector: typeof import('./connector').default

types/interceptors.d.ts

@@ -25,7 +25,6 @@ declare namespace Interceptors {
     affinity?: 4 | 6
   }
 
-  export function createRedirectInterceptor (opts: RedirectInterceptorOpts): Dispatcher.DispatcherComposeInterceptor
   export function dump (opts?: DumpInterceptorOpts): Dispatcher.DispatcherComposeInterceptor
   export function retry (opts?: RetryInterceptorOpts): Dispatcher.DispatcherComposeInterceptor
   export function redirect (opts?: RedirectInterceptorOpts): Dispatcher.DispatcherComposeInterceptor