Added keepProxy to not rewrite the URL.

README.md

@@ -79,6 +79,13 @@ An URL (including protocol) that represents the target server to use for proxyin
 
 The prefix to mount this plugin on. All the requests to the current server starting with the given prefix will be proxied to the provided upstream.
 
+The prefix will be removed from the URL when forwarding the HTTP
+request.
+
+### rewritePrefix
+
+Rewrite the prefix to the specified string. Default: `''`.
+
 ### beforeHandler
 
 A `beforeHandler` to be applied on all routes. Useful for performing actions before the proxy is executed (e.g. check for authentication).

index.js

@@ -8,6 +8,7 @@ module.exports = async function (fastify, opts) {
   }
 
   const beforeHandler = opts.beforeHandler
+  const rewritePrefix = opts.rewritePrefix || ''
 
   const fromOpts = Object.assign({}, opts)
   fromOpts.base = opts.upstream
@@ -26,7 +27,8 @@ module.exports = async function (fastify, opts) {
   fastify.all('/*', { beforeHandler }, reply)
 
   function reply (request, reply) {
-    var dest = request.req.url.replace(this.basePath, '')
+    var dest = request.req.url
+    dest = dest.replace(this.basePath, rewritePrefix)
     reply.from(dest || '/', opts.replyOptions)
   }
 }

test.js

@@ -23,6 +23,10 @@ async function run () {
     throw new Error('kaboom')
   })
 
+  origin.get('/api2/a', async (request, reply) => {
+    return 'this is /api2/a'
+  })
+
   await origin.listen(0)
 
   tearDown(origin.close.bind(origin))
@@ -179,6 +183,25 @@ async function run () {
     const { headers } = await got(`http://localhost:${proxyServer.server.address().port}/api`)
     t.match(headers, { 'x-test': 'test' })
   })
+
+  test('keepPrefix true', async (t) => {
+    const proxyServer = Fastify()
+
+    proxyServer.register(proxy, {
+      upstream: `http://localhost:${origin.server.address().port}`,
+      prefix: '/api',
+      rewritePrefix: '/api2'
+    })
+
+    await proxyServer.listen(0)
+
+    t.tearDown(() => {
+      proxyServer.close()
+    })
+
+    const firstProxyPrefix = await got(`http://localhost:${proxyServer.server.address().port}/api/a`)
+    t.equal(firstProxyPrefix.body, 'this is /api2/a')
+  })
 }
 
 run()