SCRIPT eval (when failing due to NOSCRIPT) can retry when using the sync API,...

SCRIPT eval (when failing due to NOSCRIPT) can retry when using the sync API, since there can be no competing commands (but not via the async API)

StackExchange.Redis.Tests/Scripting.cs

@@ -30,7 +30,9 @@ public void TestBasicScripting()
         }
 
         [Test]
-        public void CheckLoads()
+        [TestCase(true)]
+        [TestCase(false)]
+        public void CheckLoads(bool async)
         {
             using (var conn0 = Create(allowAdmin: true))
             using (var conn1 = Create(allowAdmin: true))
@@ -57,14 +59,25 @@ public void CheckLoads()
                 server.ScriptFlush();
                 Assert.IsFalse(server.ScriptExists(script));
                 db.Ping();
+
+                if (async)
+                {
                     // now: fails the first time
                     try
                     {
-                    Assert.IsTrue((bool)db.ScriptEvaluate(script));
+                        db.Wait(db.ScriptEvaluateAsync(script));
                         Assert.Fail();
-                } catch(RedisServerException ex)
+                    }
+                    catch(AggregateException ex)
                     {
-                    Assert.IsTrue(ex.Message == "NOSCRIPT No matching script. Please use EVAL.");
+                        Assert.AreEqual(1, ex.InnerExceptions.Count);
+                        Assert.IsInstanceOf<RedisServerException>(ex.InnerExceptions[0]);
+                        Assert.AreEqual("NOSCRIPT No matching script. Please use EVAL.", ex.InnerExceptions[0].Message);
+                    }
+                } else
+                {
+                    // just works; magic
+                    Assert.IsTrue((bool)db.ScriptEvaluate(script));
                 }
 
                 // but gets marked as unloaded, so we can use it again...

StackExchange.Redis/StackExchange/Redis/CommandFlags.cs

@@ -54,5 +54,7 @@ public enum CommandFlags
         NoRedirect = 64,
 
         // 128: used for "internal call"; never user-specified, so not visible on the public API
+
+        // 256: used for "retry"; never user-specified, so not visible on the public API
     }
 }

StackExchange.Redis/StackExchange/Redis/Message.cs

@@ -66,7 +66,9 @@ abstract class Message : ICompletable
         internal const CommandFlags InternalCallFlag = (CommandFlags)128;
         protected RedisCommand command;
 
-        private const CommandFlags AskingFlag = (CommandFlags)32;
+        private const CommandFlags AskingFlag = (CommandFlags)32,
+                                   ScriptUnavailableFlag = (CommandFlags)256;
+
         const CommandFlags MaskMasterServerPreference = CommandFlags.DemandMaster | CommandFlags.DemandSlave | CommandFlags.PreferMaster | CommandFlags.PreferSlave;
 
         private const CommandFlags UserSelectableFlags
@@ -162,6 +164,15 @@ public bool IsAsking
             get { return (flags & AskingFlag) != 0; }
         }
 
+        internal bool IsScriptUnavailable
+        {
+            get { return (flags & ScriptUnavailableFlag) != 0; }
+        }
+        internal void SetScriptUnavailable()
+        {
+            flags |= ScriptUnavailableFlag;
+        }
+
         public bool IsFireAndForget
         {
             get { return (flags & CommandFlags.FireAndForget) != 0; }

StackExchange.Redis/StackExchange/Redis/RedisDatabase.cs

@@ -759,7 +759,15 @@ public Task<long> PublishAsync(RedisChannel channel, RedisValue message, Command
         public RedisResult ScriptEvaluate(string script, RedisKey[] keys = null, RedisValue[] values = null, CommandFlags flags = CommandFlags.None)
         {
             var msg = new ScriptEvalMessage(Db, flags, RedisCommand.EVAL, script, keys ?? RedisKey.EmptyArray, values ?? RedisValue.EmptyArray);
+            try
+            {
                 return ExecuteSync(msg, ResultProcessor.ScriptResult);
+            } catch(RedisServerException)
+            {
+                // could be a NOSCRIPT; for a sync call, we can re-issue that without problem
+                if(msg.IsScriptUnavailable) return ExecuteSync(msg, ResultProcessor.ScriptResult);
+                throw;
+            }
         }
 
         public Task<RedisResult> ScriptEvaluateAsync(string script, RedisKey[] keys = null, RedisValue[] values = null, CommandFlags flags = CommandFlags.None)

StackExchange.Redis/StackExchange/Redis/ResultProcessor.cs

@@ -985,6 +985,7 @@ public override bool SetResult(PhysicalConnection connection, Message message, R
                 if (result.Type == ResultType.Error && result.AssertStarts(NOSCRIPT))
                 { // scripts are not flushed individually, so assume the entire script cache is toast ("SCRIPT FLUSH")
                     connection.Bridge.ServerEndPoint.FlushScripts();
+                    message.SetScriptUnavailable();
                 }
                 // and apply usual processing for the rest
                 return base.SetResult(connection, message, result);