Do not throw a null reference from request.GetDisplayUrl() (#1057)

Author: filipw

src/Microsoft.AspNetCore.Http.Extensions/UriHelper.cs

@@ -195,17 +195,18 @@ public static string GetEncodedPathAndQuery(this HttpRequest request)
         /// <returns></returns>
         public static string GetDisplayUrl(this HttpRequest request)
         {
-            var host = request.Host.Value;
-            var pathBase = request.PathBase.Value;
-            var path = request.Path.Value;
-            var queryString = request.QueryString.Value;
+            var scheme = request.Scheme ?? string.Empty;            
+            var host = request.Host.Value ?? string.Empty;
+            var pathBase = request.PathBase.Value ?? string.Empty;
+            var path = request.Path.Value ?? string.Empty;
+            var queryString = request.QueryString.Value ?? string.Empty;
 
             // PERF: Calculate string length to allocate correct buffer size for StringBuilder.
-            var length = request.Scheme.Length + SchemeDelimiter.Length + host.Length
+            var length = scheme.Length + SchemeDelimiter.Length + host.Length
                 + pathBase.Length + path.Length + queryString.Length;
 
             return new StringBuilder(length)
-                .Append(request.Scheme)
+                .Append(scheme)
                 .Append(SchemeDelimiter)
                 .Append(host)
                 .Append(pathBase)

test/Microsoft.AspNetCore.Http.Extensions.Tests/UriHelperTests.cs

@@ -55,17 +55,19 @@ public void GetEncodedUrlFromRequest()
             Assert.Equal("http://my.xn--host-cpd:80/un%3Fescaped/base/un%3Fescaped?name=val%23ue", request.GetEncodedUrl());
         }
 
-        [Fact]
-        public void GetDisplayUrlFromRequest()
+        [Theory]
+        [InlineData("/un?escaped/base")]
+        [InlineData(null)]
+        public void GetDisplayUrlFromRequest(string pathBase)
         {
             var request = new DefaultHttpContext().Request;
             request.Scheme = "http";
             request.Host = new HostString("my.HoΨst:80");
-            request.PathBase = new PathString("/un?escaped/base");
+            request.PathBase = new PathString(pathBase);
             request.Path = new PathString("/un?escaped");
             request.QueryString = new QueryString("?name=val%23ue");
 
-            Assert.Equal("http://my.hoψst:80/un?escaped/base/un?escaped?name=val%23ue", request.GetDisplayUrl());
+            Assert.Equal("http://my.hoψst:80" + pathBase + "/un?escaped?name=val%23ue", request.GetDisplayUrl());
         }
 
         [Theory]