Support paths within base (#148)

This use case is relied upon by fast-proxy and it was working with
the Node.js core client but not with Undici.

lib/request.js

@@ -27,9 +27,9 @@ function buildRequest (opts) {
     'unix+http:': { base: http, request: unixRequest },
     'unix+https:': { base: https, request: unixRequest }
   }
-  const baseUrl = opts.base
   const http2Opts = getHttp2Opts(opts)
   const httpOpts = getHttpOpts(opts)
+  const baseUrl = opts.base && new URL(opts.base).origin
   const undiciOpts = opts.undici || {}
   let http2Client
   let undiciAgent

test/core-with-path-in-base.js

@@ -0,0 +1,50 @@
+'use strict'
+
+const t = require('tap')
+const Fastify = require('fastify')
+const From = require('..')
+const http = require('http')
+const get = require('simple-get').concat
+
+const instance = Fastify()
+
+t.plan(11)
+t.tearDown(instance.close.bind(instance))
+
+const target = http.createServer((req, res) => {
+  t.pass('request proxied')
+  t.equal(req.method, 'GET')
+  t.equal(req.url, '/hello')
+  t.equal(req.headers.connection, 'close')
+  res.statusCode = 205
+  res.setHeader('Content-Type', 'text/plain')
+  res.setHeader('x-my-header', 'hello!')
+  res.end('hello world')
+})
+
+instance.get('/', (request, reply) => {
+  reply.from('/hello')
+})
+
+t.tearDown(target.close.bind(target))
+
+target.listen(0, (err) => {
+  t.error(err)
+
+  instance.register(From, {
+    base: `http://localhost:${target.address().port}/hello`,
+    http: true
+  })
+
+  instance.listen(0, (err) => {
+    t.error(err)
+
+    get(`http://localhost:${instance.server.address().port}`, (err, res, data) => {
+      t.error(err)
+      t.equal(res.headers['content-type'], 'text/plain')
+      t.equal(res.headers['x-my-header'], 'hello!')
+      t.equal(res.statusCode, 205)
+      t.equal(data.toString(), 'hello world')
+    })
+  })
+})

test/undici-with-path-in-base.js

@@ -0,0 +1,50 @@
+'use strict'
+
+const t = require('tap')
+const Fastify = require('fastify')
+const From = require('..')
+const http = require('http')
+const get = require('simple-get').concat
+
+const instance = Fastify()
+
+t.plan(11)
+t.tearDown(instance.close.bind(instance))
+
+const target = http.createServer((req, res) => {
+  t.pass('request proxied')
+  t.equal(req.method, 'GET')
+  t.equal(req.url, '/hello')
+  t.equal(req.headers.connection, 'keep-alive')
+  res.statusCode = 205
+  res.setHeader('Content-Type', 'text/plain')
+  res.setHeader('x-my-header', 'hello!')
+  res.end('hello world')
+})
+
+instance.get('/', (request, reply) => {
+  reply.from('/hello')
+})
+
+t.tearDown(target.close.bind(target))
+
+target.listen(0, (err) => {
+  t.error(err)
+
+  instance.register(From, {
+    base: `http://localhost:${target.address().port}/hello`,
+    undici: true
+  })
+
+  instance.listen(0, (err) => {
+    t.error(err)
+
+    get(`http://localhost:${instance.server.address().port}`, (err, res, data) => {
+      t.error(err)
+      t.equal(res.headers['content-type'], 'text/plain')
+      t.equal(res.headers['x-my-header'], 'hello!')
+      t.equal(res.statusCode, 205)
+      t.equal(data.toString(), 'hello world')
+    })
+  })
+})