Fix handling of RedirectLocation header

Author: stephentoub

src/System.Net.HttpListener/src/System/Net/Managed/HttpListener.Managed.cs

@@ -68,9 +68,10 @@ public bool UnsafeConnectionNtlmAuthentication
         public void Stop()
         {
             if (NetEventSource.IsEnabled) NetEventSource.Enter(this);
-            try
+
+            lock (_internalLock)
             {
-                lock (_internalLock)
+                try
                 {
                     CheckDisposed();
                     if (_state == State.Stopped)
@@ -79,19 +80,18 @@ public void Stop()
                     }
 
                     Close(false);
-
+                }
+                catch (Exception exception)
+                {
+                    if (NetEventSource.IsEnabled) NetEventSource.Error(this, $"Stop {exception}");
+                    throw;
+                }
+                finally
+                {
                     _state = State.Stopped;
+                    if (NetEventSource.IsEnabled) NetEventSource.Exit(this);
                 }
             }
-            catch (Exception exception)
-            {
-                if (NetEventSource.IsEnabled) NetEventSource.Error(this, $"Stop {exception}");
-                throw;
-            }
-            finally
-            {
-                if (NetEventSource.IsEnabled) NetEventSource.Exit(this);
-            }
         }
 
         public void Abort()

src/System.Net.HttpListener/src/System/Net/Managed/HttpListenerContext.Managed.cs

@@ -97,6 +97,7 @@ public Task<HttpListenerWebSocketContext> AcceptWebSocketAsync(string subProtoco
         public Task<HttpListenerWebSocketContext> AcceptWebSocketAsync(string subProtocol, int receiveBufferSize, TimeSpan keepAliveInterval, ArraySegment<byte> internalBuffer)
         {
             WebSocketValidate.ValidateArraySegment(internalBuffer, nameof(internalBuffer));
+            HttpWebSocket.ValidateOptions(subProtocol, receiveBufferSize, HttpWebSocket.MinSendBufferSize, keepAliveInterval);
             return HttpWebSocket.AcceptWebSocketAsyncCore(this, subProtocol, receiveBufferSize, keepAliveInterval, internalBuffer);
         }
     }

src/System.Net.HttpListener/src/System/Net/Managed/HttpListenerResponse.Managed.cs

@@ -316,6 +316,9 @@ internal void SendHeaders(bool closing, MemoryStream ms, bool isWebSocketHandsha
             SentHeaders = !isWebSocketHandshake;
         }
 
+        private static bool HeaderCanHaveEmptyValue(string name) =>
+            !string.Equals(name, HttpKnownHeaderNames.Location, StringComparison.OrdinalIgnoreCase);
+
         private static string FormatHeaders(WebHeaderCollection headers)
         {
             var sb = new StringBuilder();
@@ -324,9 +327,34 @@ private static string FormatHeaders(WebHeaderCollection headers)
             {
                 string key = headers.GetKey(i);
                 string[] values = headers.GetValues(i);
+
+                int startingLength = sb.Length;
+
+                sb.Append(key).Append(": ");
+                bool anyValues = false;
                 for (int j = 0; j < values.Length; j++)
                 {
-                    sb.Append(key).Append(": ").Append(values[j]).Append("\r\n");
+                    string value = values[j];
+                    if (!string.IsNullOrWhiteSpace(value))
+                    {
+                        if (anyValues)
+                        {
+                            sb.Append(", ");
+                        }
+                        sb.Append(value);
+                        anyValues = true;
+                    }
+                }
+
+                if (anyValues || HeaderCanHaveEmptyValue(key))
+                {
+                    // Complete the header
+                    sb.Append("\r\n");
+                }
+                else
+                {
+                    // Empty header; remove it.
+                    sb.Length = startingLength;
                 }
             }
 

src/System.Net.HttpListener/tests/HttpListenerResponseTests.Headers.cs

@@ -209,8 +209,7 @@ public async Task RedirectLocation_SetAndSend_Success(string redirectLocation, i
         [InlineData(null, null)]
         [InlineData("", null)]
         [InlineData("\r \t \n", "")]
-        // The managed implementation should set Location directly in Headers rather than track it with its own variable.
-        [ConditionalTheory(nameof(Helpers) + "." + nameof(Helpers.IsWindowsImplementation))] // [ActiveIssue(19972, TestPlatforms.AnyUnix)]
+        [ConditionalTheory(nameof(PlatformDetection) + "." + nameof(PlatformDetection.IsNotOneCoreUAP))]
         public async Task RedirectLocation_SetNullOrEmpty_ResetsRedirectLocation(string redirectLocation, string expectedRedirectLocation)
         {
             using (HttpListenerResponse response = await GetResponse())

src/System.Net.HttpListener/tests/HttpListenerResponseTests.cs

@@ -263,8 +263,7 @@ public async Task CloseResponseEntity_EmptyResponseEntity_Success(bool willBlock
             }
         }
 
-        // The managed implementation should not register as disposed before setting ContentLength - this causes an ObjectDisposedException.
-        [ConditionalTheory(nameof(Helpers) + "." + nameof(Helpers.IsWindowsImplementation))] // [ActiveIssue(19975, TestPlatforms.AnyUnix)]
+        [ConditionalTheory(nameof(Helpers) + "." + nameof(Helpers.IsWindowsImplementation))] // [ActiveIssue(20201, TestPlatforms.AnyUnix)]
         [InlineData(true)]
         [InlineData(false)]
         public async Task CloseResponseEntity_AllContentLengthAlreadySent_DoesNotSendEntity(bool willBlock)