fix(undiciRequest): file uploading (#11320)

* fix(undiciRequest): file uploading

* fix: different approach

* fix: revert to the previous approach

---------

Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>

packages/rest/src/strategies/undiciRequest.ts

@@ -1,12 +1,14 @@
 import { STATUS_CODES } from 'node:http';
 import { URLSearchParams } from 'node:url';
 import { types } from 'node:util';
-import { type RequestInit, request, Headers, FormData as UndiciFormData } from 'undici';
+import { type RequestInit, request, Headers, FormData as UndiciFormData, Agent } from 'undici';
 import type { HeaderRecord } from 'undici/types/header.js';
 import type { ResponseLike } from '../shared.js';
 
 export type RequestOptions = Exclude<Parameters<typeof request>[1], undefined>;
 
+let localAgent: Agent | null = null;
+
 export async function makeRequest(url: string, init: RequestInit): Promise<ResponseLike> {
 	// The cast is necessary because `headers` and `method` are narrower types in `undici.request`
 	// our request path guarantees they are of acceptable type for `undici.request`
@@ -14,6 +16,15 @@ export async function makeRequest(url: string, init: RequestInit): Promise<Respo
 		...init,
 		body: await resolveBody(init.body),
 	} as RequestOptions;
+
+	// Mismatched dispatchers from the Node.js-bundled undici and package-installed undici breaks file uploads.
+	// So we ensure that we always pass an Agent to request()
+	// https://github.com/nodejs/node/issues/59012
+	if (!options.dispatcher) {
+		localAgent ??= new Agent();
+		options.dispatcher = localAgent;
+	}
+
 	const res = await request(url, options);
 	return {
 		body: res.body,