fix(qs): preserve fromParameters query params

index.js

@@ -605,29 +605,31 @@ async function fastifyHttpProxy (fastify, opts) {
       }
 
       dest = dest.replace(prefixPathWithVariables, rewritePrefixWithVariables)
-      if (queryParams) {
-        dest += `?${qs.stringify(queryParams)}`
-      }
     } else {
       dest = dest.replace(prefix, rewritePrefix)
     }
 
+    if (queryParams) {
+      dest += `?${qs.stringify(queryParams)}`
+    }
+
     return { url: dest || '/', options: replyOpts }
   }
 
   function handler (request, reply) {
     const { url, options } = fromParameters(request.url, request.params, this.prefix)
+    const dest = url.split('?', 1)[0]
 
     if (request.raw[kWs]) {
       reply.hijack()
       try {
-        wsProxy.handleUpgrade(request, url, noop)
+        wsProxy.handleUpgrade(request, dest, noop)
       } /* c8 ignore start */ catch (err) {
         request.log.warn({ err }, 'websocket proxy error')
       } /* c8 ignore stop */
       return
     }
-    reply.from(url, options)
+    reply.from(dest, options)
   }
 
   fastify.decorateReply('fromParameters', fromParameters)

test/test.js

@@ -38,6 +38,10 @@ async function run () {
     return 'this is /api2/a'
   })
 
+  origin.get('/api2/echo-query', async (request) => {
+    return `query: ${JSON.stringify(request.query)}`
+  })
+
   origin.get('/variable-api/:id/endpoint', async (request) => {
     return `this is "variable-api" endpoint with id ${request.params.id}`
   })
@@ -900,6 +904,27 @@ async function run () {
     }
   })
 
+  test('fromParameters should preserve query params with non-parameterized prefix', async t => {
+    let fromParametersUrl
+    const server = Fastify()
+    server.register(proxy, {
+      upstream: `http://localhost:${origin.server.address().port}`,
+      prefix: '/api',
+      rewritePrefix: '/api2',
+      preHandler (request, reply, done) {
+        const { url } = reply.fromParameters(request.url, request.params, '/api')
+        fromParametersUrl = url
+        done()
+      }
+    })
+
+    await server.listen({ port: 0 })
+    t.after(() => server.close())
+
+    await fetch(`http://localhost:${server.server.address().port}/api/echo-query?foo=bar&baz=qux`)
+    t.assert.strictEqual(fromParametersUrl, '/api2/echo-query?foo=bar&baz=qux')
+  })
+
   test('preRewrite handler', async t => {
     const proxyServer = Fastify()