types: Allow to pass any requestable undici instance

types/index.d.ts

@@ -28,7 +28,7 @@ import {
   AgentOptions as SecureAgentOptions,
   RequestOptions as SecureRequestOptions
 } from 'https'
-import { Pool, ProxyAgent } from 'undici'
+import { Pool, ProxyAgent, Dispatcher } from 'undici'
 
 declare module 'fastify' {
   interface FastifyReply {
@@ -104,7 +104,7 @@ declare namespace fastifyReplyFrom {
     disableCache?: boolean;
     http?: HttpOptions;
     http2?: Http2Options | boolean;
-    undici?: Pool.Options & { proxy?: string | URL | ProxyAgent.Options };
+    undici?: Pool.Options & { proxy?: string | URL | ProxyAgent.Options } | { request: Dispatcher['request'] };
     contentTypesToEncode?: string[];
     retryMethods?: (HTTPMethods | 'TRACE')[];
     maxRetriesOn503?: number;

types/index.test-d.ts

@@ -4,6 +4,7 @@ import { IncomingHttpHeaders } from 'http2'
 import * as https from 'node:https'
 import { AddressInfo } from 'net'
 import { expectType } from 'tsd'
+import { Agent, Client, Dispatcher, Pool } from 'undici'
 import replyFrom, { FastifyReplyFromOptions } from '..'
 // @ts-ignore
 import tap from 'tap'
@@ -158,6 +159,34 @@ async function main () {
   })
   await undiciInstance.ready()
 
+  const undiciInstanceAgent = fastify()
+  undiciInstance.register(replyFrom, {
+    base: 'http://example2.com',
+    undici: new Agent()
+  })
+  await undiciInstanceAgent.ready()
+
+  const undiciInstancePool = fastify()
+  undiciInstance.register(replyFrom, {
+    base: 'http://example2.com',
+    undici: new Pool('http://example2.com')
+  })
+  await undiciInstancePool.ready()
+
+  const undiciInstanceClient = fastify()
+  undiciInstance.register(replyFrom, {
+    base: 'http://example2.com',
+    undici: new Client('http://example2.com')
+  })
+  await undiciInstanceClient.ready()
+
+  const undiciInstanceDispatcher = fastify()
+  undiciInstance.register(replyFrom, {
+    base: 'http://example2.com',
+    undici: new Dispatcher()
+  })
+  await undiciInstanceDispatcher.ready()
+
   tap.pass('done')
   tap.end()
 }