throw if req.ip is undefined

fixes #254 (well, not really, but at least makes it more obvious)

.gitignore

@@ -1,3 +1,4 @@
 /node_modules/
 npm-debug.log
-.idea/
+.idea/
+.vscode/

README.md

@@ -177,7 +177,7 @@ Defaults to `false`. Behavior and name will likely change in future releases.
 
 Function used to generate keys.
 
-Defaults to req.ip:
+Defaults to req.ip, similar to this:
 
 ```js
 function (req /*, res*/) {

lib/express-rate-limit.js

@@ -18,6 +18,11 @@ function RateLimit(options) {
       skipSuccessfulRequests: false, // Do not count successful requests
       // 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?"
+          );
+        }
         return req.ip;
       },
       skip: function (/*req, res*/) {

test/express-rate-limit-test.js

@@ -4,6 +4,7 @@ const assert = require("assert");
 const request = require("supertest");
 const sinon = require("sinon");
 const rateLimit = require("../lib/express-rate-limit.js");
+const { promisify } = require("util");
 
 // todo: look into using http://sinonjs.org/docs/#clock instead of actually letting the tests wait on setTimeouts
 
@@ -75,18 +76,24 @@ describe("express-rate-limit node module", () => {
     };
   }
 
-  it("should not allow the use of a store that is not valid", (done) => {
+  it("should not allow the use of a store that is not valid", async () => {
     function InvalidStore() {}
 
-    try {
+    assert.throws(() => {
       rateLimit({
         store: new InvalidStore(),
       });
-    } catch (e) {
-      return done();
-    }
+    }, /store/);
+  });
 
-    done(new Error("It allowed an invalid store"));
+  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"
+    );
   });
 
   it("should let the first request through", async () => {
@@ -476,7 +483,7 @@ describe("express-rate-limit node module", () => {
     assert(store.decrement_was_called, "decrement was not called on the store");
   });
 
-  it.only("should decrement hits with closed response and skipFailedRequests", async () => {
+  it("should decrement hits with closed response and skipFailedRequests", async () => {
     clock.restore();
 
     const store = new MockStore();