Fix proxy bypass return false

lib/Server.js

@@ -382,12 +382,23 @@ class Server {
               }
 
               const bypass = typeof proxyConfig.bypass === 'function';
-
+              const bypassRawValue = bypass
+                ? proxyConfig.bypass(req, res, proxyConfig)
+                : null;
               const bypassUrl =
-                (bypass && proxyConfig.bypass(req, res, proxyConfig)) || false;
+                typeof bypassRawValue === 'string'
+                  ? bypassRawValue
+                  : typeof bypassRawValue === 'boolean' &&
+                    bypassRawValue === false;
 
               if (bypassUrl) {
-                req.url = bypassUrl;
+                if (typeof bypassUrl === 'boolean') {
+                  req.url = null;
+                }
+
+                if (typeof bypassUrl === 'string') {
+                  req.url = bypassUrl;
+                }
 
                 next();
               } else if (proxyMiddleware) {

test/Proxy.test.js

@@ -23,6 +23,15 @@ const proxyOptionPathsAsProperties = {
       if (/\.html$/.test(req.path)) {
         return '/index.html';
       }
+
+      return null;
+    },
+  },
+  '/proxyfalse': {
+    bypass(req) {
+      if (/\/proxyfalse$/.test(req.path)) {
+        return false;
+      }
     },
   },
 };
@@ -116,6 +125,10 @@ describe('Proxy', () => {
       it('should pass through a proxy when a bypass function returns null', (done) => {
         req.get('/foo.js').expect(200, /Hey/, done);
       });
+
+      it('should not pass through a proxy when a bypass function returns false', (done) => {
+        req.get('/proxyfalse').expect(404, done);
+      });
     });
   });