first pass

index.js

@@ -1,5 +1,5 @@
-const Layer = require('express/lib/router/layer');
-const Router = require('express/lib/router');
+const { version: expressVersion } = require('express/package.json');
+const express = require('express');
 
 const last = (arr = []) => arr[arr.length - 1];
 const noop = Function.prototype;
@@ -10,7 +10,6 @@ function copyFnProps(oldFn, newFn) {
   });
   return newFn;
 }
-
 function wrap(fn) {
   const newFn = function newFn(...args) {
     const ret = fn.apply(this, args);
@@ -24,24 +23,32 @@ function wrap(fn) {
   });
   return copyFnProps(fn, newFn);
 }
-
 function patchRouterParam() {
-  const originalParam = Router.prototype.constructor.param;
-  Router.prototype.constructor.param = function param(name, fn) {
+  const originalParam = express.Router.prototype.constructor.param;
+  express.Router.prototype.constructor.param = function param(name, fn) {
     fn = wrap(fn);
     return originalParam.call(this, name, fn);
   };
 }
 
-Object.defineProperty(Layer.prototype, 'handle', {
-  enumerable: true,
-  get() {
-    return this.__handle;
-  },
-  set(fn) {
-    fn = wrap(fn);
-    this.__handle = fn;
-  },
-});
-
 patchRouterParam();
+
+if (expressVersion[0] > 4) {
+  // eslint-disable-next-line no-console
+  console.warn(`deprecated: Package express-async-errors works with version 4.x.x of Express, you are using ${expressVersion} which supports async route handlers natively`);
+} else {
+  // setup module
+  // eslint-disable-next-line global-require
+  const Layer = require('express/lib/router/layer');
+
+  Object.defineProperty(Layer.prototype, 'handle', {
+    enumerable: true,
+    get() {
+      return this.__handle;
+    },
+    set(fn) {
+      fn = wrap(fn);
+      this.__handle = fn;
+    },
+  });
+}