Add retries to HttpClientSlim on macOS. (dotnet/extensions#1807)

\n\nCommit migrated from d4d110a838

src/Testing/src/HttpClientSlim.cs

@@ -8,6 +8,7 @@ using System.Net;
 using System.Net.Http;
 using System.Net.Security;
 using System.Net.Sockets;
+using System.Runtime.InteropServices;
 using System.Security.Authentication;
 using System.Text;
 using System.Threading.Tasks;
@@ -23,6 +24,8 @@ namespace Microsoft.AspNetCore.Testing
             => await GetStringAsync(new Uri(requestUri), validateCertificate).ConfigureAwait(false);
 
         public static async Task<string> GetStringAsync(Uri requestUri, bool validateCertificate = true)
+        {
+            return await RetryRequest(async () =>
             {
                 using (var stream = await GetStream(requestUri, validateCertificate).ConfigureAwait(false))
                 {
@@ -35,6 +38,7 @@ namespace Microsoft.AspNetCore.Testing
 
                     return await ReadResponse(stream).ConfigureAwait(false);
                 }
+            });
         }
 
         internal static string GetHost(Uri requestUri)
@@ -61,6 +65,8 @@ namespace Microsoft.AspNetCore.Testing
             => await PostAsync(new Uri(requestUri), content, validateCertificate).ConfigureAwait(false);
 
         public static async Task<string> PostAsync(Uri requestUri, HttpContent content, bool validateCertificate = true)
+        {
+            return await RetryRequest(async () =>
             {
                 using (var stream = await GetStream(requestUri, validateCertificate))
                 {
@@ -77,6 +83,7 @@ namespace Microsoft.AspNetCore.Testing
 
                     return await ReadResponse(stream).ConfigureAwait(false);
                 }
+            });
         }
 
         private static async Task<string> ReadResponse(Stream stream)
@@ -94,6 +101,33 @@ namespace Microsoft.AspNetCore.Testing
             }
         }
 
+        private static async Task<string> RetryRequest(Func<Task<string>> retryBlock)
+        {
+            var retryCount = 1;
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
+            {
+                retryCount = 3;
+            }
+
+            for (var retry = 0; retry < retryCount; retry++)
+            {
+                try
+                {
+                    return await retryBlock().ConfigureAwait(false);
+                }
+                catch (InvalidDataException)
+                {
+                    if (retry == retryCount - 1)
+                    {
+                        throw;
+                    }
+                }
+            }
+
+            // This will never be hit.
+            throw new NotSupportedException();
+        }
+
         private static HttpStatusCode GetStatus(string response)
         {
             var statusStart = response.IndexOf(' ') + 1;