avoid warning with exposeHeadRoute route option (fastify#2797)

Author: mcollina

lib/route.js

@@ -235,6 +235,8 @@ function buildRouting (options) {
         opts.schemaErrorFormatter || this[kSchemaErrorFormatter]
       )
 
+      const headRouteExists = router.find('HEAD', path) != null
+
       try {
         router.on(opts.method, opts.url, { version: opts.version }, routeHandler, context)
       } catch (err) {
@@ -245,7 +247,6 @@ function buildRouting (options) {
       const { exposeHeadRoute } = opts
       const hasRouteExposeHeadRouteFlag = exposeHeadRoute != null
       const shouldExposeHead = hasRouteExposeHeadRouteFlag ? exposeHeadRoute : globalExposeHeadRoutes
-      const headRouteExists = router.find('HEAD', path) != null
 
       if (shouldExposeHead && options.method === 'GET' && !headRouteExists) {
         const onSendHandlers = parseHeadOnSendHandlers(opts.onSend)

test/route.test.js

@@ -819,6 +819,32 @@ test('HEAD route should respect custom onSend handlers', t => {
   })
 })
 
+test('no warning for exposeHeadRoute', async t => {
+  const fastify = Fastify()
+
+  fastify.route({
+    method: 'GET',
+    path: '/more-coffee',
+    exposeHeadRoute: true,
+    async handler () {
+      return 'hello world'
+    }
+  })
+
+  const listener = (w) => {
+    console.error(w)
+    t.fail('no warning')
+  }
+
+  process.on('warning', listener)
+
+  await fastify.listen(0)
+
+  process.removeListener('warning', listener)
+
+  await fastify.close()
+})
+
 test("HEAD route should handle stream.on('error')", t => {
   t.plan(6)