Warn if "referer" returns "referrer", or vice versa

Author: rileyjshaw

lib/request.js

@@ -74,11 +74,15 @@ req.header = function header(name) {
   var lc = name.toLowerCase();
 
   switch (lc) {
-    case 'referrer':
-      deprecate('The "Referrer" header is non-standard, and special-casing for it will be dropped in future versions.');
     case 'referer':
-      return this.headers.referrer
-        || this.headers.referer;
+    case 'referrer':
+      var isNameNonstandard = lc === 'referrer';
+      var isHeaderNonstandard = !!this.headers.referrer;
+      // Warn if "referer" returns "referrer", or vice versa.
+      if (isNameNonstandard !== isHeaderNonstandard) {
+        deprecate('The "Referrer" header is non-standard, and special-casing for it will be dropped in future versions.');
+      }
+      return this.headers.referrer || this.headers.referer;
     default:
       return this.headers[lc];
   }