change missing req.ip from thrown error to logged error.

relates to #254, #260

lib/express-rate-limit.js

@@ -19,8 +19,8 @@ function RateLimit(options) {
       // allows to create custom keys (by default user IP is used)
       keyGenerator: function (req /*, res*/) {
         if (!req.ip) {
-          throw new Error(
-            "express-rate-limit: req.ip is undefined - are you sure you're using express?"
+          console.error(
+            "express-rate-limit: req.ip is undefined - you can avoid this by providing a custom keyGenerator function, but it may be indicative of a larger issue."
           );
         }
         return req.ip;

test/express-rate-limit-test.js

@@ -3,6 +3,7 @@ const express = require("express");
 const assert = require("assert");
 const request = require("supertest");
 const sinon = require("sinon");
+const sandbox = sinon.createSandbox();
 const rateLimit = require("../lib/express-rate-limit.js");
 const { promisify } = require("util");
 
@@ -17,6 +18,7 @@ describe("express-rate-limit node module", () => {
 
   afterEach(() => {
     clock.restore();
+    sandbox.restore();
   });
 
   function createAppWith(limit) {
@@ -89,11 +91,9 @@ describe("express-rate-limit node module", () => {
   it("should error when req.ip is undefined", async () => {
     const limiter = rateLimit({});
     const { IncomingMessage, OutgoingMessage } = require("http");
-    await assert.rejects(
-      promisify(limiter)(new IncomingMessage(), new OutgoingMessage()),
-      /express/,
-      "Should error with a message about express"
-    );
+    sandbox.stub(console, "error");
+    await promisify(limiter)(new IncomingMessage(), new OutgoingMessage());
+    sandbox.assert.calledOnce(console.error);
   });
 
   it("should let the first request through", async () => {