fix CheckDatabaseMethodsUseKeys (false positive); remove all the `new...

fix CheckDatabaseMethodsUseKeys (false positive); remove all the `new SomeType[0]` usages (static and local)

StackExchange.Redis.Tests/Naming.cs

@@ -98,6 +98,7 @@ public void CheckDatabaseMethodsUseKeys(Type type)
         private static bool UsesKey(Type type)
         {
             if (type == typeof(RedisKey)) return true;
+            if (type == typeof(StreamIdPair)) return true;
 
             if (type.IsArray)
             {

StackExchange.Redis/StackExchange/Redis/ClusterConfiguration.cs

@@ -269,10 +269,6 @@ public sealed class ClusterNode :  IEquatable<ClusterNode>, IComparable<ClusterN
     {
         private static readonly ClusterNode Dummy = new ClusterNode();
 
-        private static readonly IList<ClusterNode> NoNodes = new ClusterNode[0];
-
-        private static readonly IList<SlotRange> NoSlots = new SlotRange[0];
-
         private readonly ClusterConfiguration configuration;
 
         private IList<ClusterNode> children;
@@ -322,7 +318,7 @@ internal ClusterNode(ClusterConfiguration configuration, string raw, EndPoint or
                     (slots ?? (slots = new List<SlotRange>(parts.Length - i))).Add(range);
                 }
             }
-            Slots = slots?.AsReadOnly() ?? NoSlots;
+            Slots = slots?.AsReadOnly() ?? (IList<SlotRange>)Array.Empty<SlotRange>();
             IsConnected = parts[7] == "connected"; // Can be "connected" or "disconnected"
         }
         /// <summary>
@@ -342,7 +338,7 @@ public IList<ClusterNode> Children
                         (nodes ?? (nodes = new List<ClusterNode>())).Add(node);
                     }
                 }
-                children = nodes?.AsReadOnly() ?? NoNodes;
+                children = nodes?.AsReadOnly() ?? (IList<ClusterNode>)Array.Empty<ClusterNode>();
                 return children;
             }
         }

StackExchange.Redis/StackExchange/Redis/ConnectionMultiplexer.cs

@@ -851,10 +851,7 @@ private static ConnectionMultiplexer ConnectImpl(Func<ConnectionMultiplexer> mul
 
         private string failureMessage;
         private readonly Hashtable servers = new Hashtable();
-        private volatile ServerEndPoint[] serverSnapshot = NilServers;
-
-        private static readonly ServerEndPoint[] NilServers = new ServerEndPoint[0];
-
+        private volatile ServerEndPoint[] serverSnapshot = Array.Empty<ServerEndPoint>();
         internal ServerEndPoint GetServerEndPoint(EndPoint endpoint)
         {
             if (endpoint == null) return null;

StackExchange.Redis/StackExchange/Redis/ExtensionMethods.cs

@@ -122,7 +122,6 @@ public static class ExtensionMethods
             return result;
         }
 
-        private static readonly RedisValue[] nixValues = new RedisValue[0];
         /// <summary>
         /// Create an array of RedisValues from an array of strings.
         /// </summary>
@@ -130,11 +129,10 @@ public static class ExtensionMethods
         public static RedisValue[] ToRedisValueArray(this string[] values)
         {
             if (values == null) return null;
-            if (values.Length == 0) return nixValues;
+            if (values.Length == 0) return Array.Empty<RedisValue>();
             return Array.ConvertAll(values, x => (RedisValue)x);
         }
 
-        private static readonly string[] nix = new string[0];
         /// <summary>
         /// Create an array of strings from an array of values
         /// </summary>
@@ -142,7 +140,7 @@ public static RedisValue[] ToRedisValueArray(this string[] values)
         public static string[] ToStringArray(this RedisValue[] values)
         {
             if (values == null) return null;
-            if (values.Length == 0) return nix;
+            if (values.Length == 0) return Array.Empty<string>();
             return Array.ConvertAll(values, x => (string)x);
         }
 

StackExchange.Redis/StackExchange/Redis/Message.cs

@@ -46,7 +46,6 @@ internal override void WriteImpl(PhysicalConnection physical)
 
     internal abstract class Message : ICompletable
     {
-        public static readonly Message[] EmptyArray = new Message[0];
         public readonly int Db;
 
         internal const CommandFlags InternalCallFlag = (CommandFlags)128;

StackExchange.Redis/StackExchange/Redis/RawResult.cs

@@ -212,7 +212,7 @@ internal RedisKey[] GetItemsAsKeys()
             }
             else if (items.Length == 0)
             {
-                return RedisKey.EmptyArray;
+                return Array.Empty<RedisKey>();
             }
             else
             {
@@ -246,8 +246,6 @@ internal RedisValue[] GetItemsAsValues()
                 return arr;
             }
         }
-
-        private static readonly string[] NilStrings = new string[0];
         internal string[] GetItemsAsStrings()
         {
             var items = GetItems();
@@ -257,7 +255,7 @@ internal string[] GetItemsAsStrings()
             }
             else if (items.Length == 0)
             {
-                return NilStrings;
+                return Array.Empty<string>();
             }
             else
             {
@@ -295,7 +293,7 @@ internal string[] GetItemsAsStrings()
             }
             else if (items.Length == 0)
             {
-                return new GeoPosition?[0];
+                return Array.Empty<GeoPosition?>();
             }
             else
             {

StackExchange.Redis/StackExchange/Redis/RedisChannel.cs

@@ -8,8 +8,6 @@ namespace StackExchange.Redis
     /// </summary>
     public struct RedisChannel : IEquatable<RedisChannel>
     {
-        internal static readonly RedisChannel[] EmptyArray = new RedisChannel[0];
-
         internal readonly byte[] Value;
         internal readonly bool IsPatternBased;
 

StackExchange.Redis/StackExchange/Redis/RedisDatabase.cs

@@ -302,7 +302,7 @@ public RedisValue HashGet(RedisKey key, RedisValue hashField, CommandFlags flags
         public RedisValue[] HashGet(RedisKey key, RedisValue[] hashFields, CommandFlags flags = CommandFlags.None)
         {
             if (hashFields == null) throw new ArgumentNullException(nameof(hashFields));
-            if (hashFields.Length == 0) return new RedisValue[0];
+            if (hashFields.Length == 0) return Array.Empty<RedisValue>();
             var msg = Message.Create(Database, flags, RedisCommand.HMGET, key, hashFields);
             return ExecuteSync(msg, ResultProcessor.RedisValueArray);
         }
@@ -2018,7 +2018,7 @@ public RedisValue StringGet(RedisKey key, CommandFlags flags = CommandFlags.None
         public RedisValue[] StringGet(RedisKey[] keys, CommandFlags flags = CommandFlags.None)
         {
             if (keys == null) throw new ArgumentNullException(nameof(keys));
-            if (keys.Length == 0) return new RedisValue[0];
+            if (keys.Length == 0) return Array.Empty<RedisValue>();
             var msg = Message.Create(Database, flags, RedisCommand.MGET, keys);
             return ExecuteSync(msg, ResultProcessor.RedisValueArray);
         }
@@ -2032,7 +2032,7 @@ public Task<RedisValue> StringGetAsync(RedisKey key, CommandFlags flags = Comman
         public Task<RedisValue[]> StringGetAsync(RedisKey[] keys, CommandFlags flags = CommandFlags.None)
         {
             if (keys == null) throw new ArgumentNullException(nameof(keys));
-            if (keys.Length == 0) return CompletedTask<RedisValue[]>.FromResult(new RedisValue[0], asyncState);
+            if (keys.Length == 0) return CompletedTask<RedisValue[]>.FromResult(Array.Empty<RedisValue>(), asyncState);
             var msg = Message.Create(Database, flags, RedisCommand.MGET, keys);
             return ExecuteAsync(msg, ResultProcessor.RedisValueArray);
         }
@@ -3163,12 +3163,11 @@ protected override bool SetResultCore(PhysicalConnection connection, Message mes
         private sealed class ExecuteMessage : Message
         {
             private readonly string _command;
-            private static readonly object[] NoArgs = new object[0];
             private readonly ICollection<object> args;
             public ExecuteMessage(int db, CommandFlags flags, string command, ICollection<object> args) : base(db, flags, RedisCommand.UNKNOWN)
             {
                 _command = command;
-                this.args = args ?? NoArgs;
+                this.args = args ?? Array.Empty<object>();
             }
 
             internal override void WriteImpl(PhysicalConnection physical)
@@ -3234,8 +3233,8 @@ private ScriptEvalMessage(int db, CommandFlags flags, RedisCommand command, stri
                 this.script = script;
                 this.hexHash = hexHash;
 
-                if (keys == null) keys = RedisKey.EmptyArray;
-                if (values == null) values = RedisValue.EmptyArray;
+                if (keys == null) keys = Array.Empty<RedisKey>();
+                if (values == null) values = Array.Empty<RedisValue>();
                 for (int i = 0; i < keys.Length; i++)
                     keys[i].AssertNotNull();
                 this.keys = keys;

StackExchange.Redis/StackExchange/Redis/RedisKey.cs

@@ -8,7 +8,6 @@ namespace StackExchange.Redis
     /// </summary>
     public struct RedisKey : IEquatable<RedisKey>
     {
-        internal static readonly RedisKey[] EmptyArray = new RedisKey[0];
         private readonly byte[] keyPrefix;
         private readonly object keyValue; // always either a string or a byte[]
         internal RedisKey(byte[] keyPrefix, object keyValue)

StackExchange.Redis/StackExchange/Redis/RedisTransaction.cs

@@ -173,16 +173,14 @@ protected override bool SetResultCore(PhysicalConnection connection, Message mes
 
         private class TransactionMessage : Message, IMultiMessage
         {
-            private static readonly ConditionResult[] NixConditions = new ConditionResult[0];
-            private static readonly QueuedMessage[] NixMessages = new QueuedMessage[0];
             private readonly ConditionResult[] conditions;
             public QueuedMessage[] InnerOperations { get; }
 
             public TransactionMessage(int db, CommandFlags flags, List<ConditionResult> conditions, List<QueuedMessage> operations)
                 : base(db, flags, RedisCommand.EXEC)
             {
-                this.InnerOperations = (operations == null || operations.Count == 0) ? NixMessages : operations.ToArray();
-                this.conditions = (conditions == null || conditions.Count == 0) ? NixConditions : conditions.ToArray();
+                this.InnerOperations = (operations == null || operations.Count == 0) ? Array.Empty<QueuedMessage>() : operations.ToArray();
+                this.conditions = (conditions == null || conditions.Count == 0) ? Array.Empty<ConditionResult>(): conditions.ToArray();
             }
 
             public bool IsAborted => command != RedisCommand.EXEC;

StackExchange.Redis/StackExchange/Redis/ResultProcessor.cs

@@ -506,8 +506,6 @@ protected override HashEntry Parse(RawResult first, RawResult second)
 
         internal abstract class ValuePairInterleavedProcessorBase<T> : ResultProcessor<T[]>
         {
-            private static readonly T[] nix = new T[0];
-
             public bool TryParse(RawResult result, out T[] pairs)
             {
                 switch (result.Type)
@@ -523,7 +521,7 @@ public bool TryParse(RawResult result, out T[] pairs)
                             int count = arr.Length / 2;
                             if (count == 0)
                             {
-                                pairs = nix;
+                                pairs = Array.Empty<T>();
                             }
                             else
                             {
@@ -1069,7 +1067,7 @@ protected override bool SetResultCore(PhysicalConnection connection, Message mes
                         RedisChannel[] final;
                         if (arr.Length == 0)
                         {
-                            final = RedisChannel.EmptyArray;
+                            final = Array.Empty<RedisChannel>();
                         }
                         else
                         {
@@ -1347,7 +1345,7 @@ protected override bool SetResultCore(PhysicalConnection connection, Message mes
                 if (result.IsNull)
                 {
                     // Server returns 'nil' if no entries are returned for the given stream.
-                    SetResult(message, new RedisStreamEntry[0]);
+                    SetResult(message, Array.Empty<RedisStreamEntry>());
                     return true;
                 }
 
@@ -1647,7 +1645,7 @@ protected override bool SetResultCore(PhysicalConnection connection, Message mes
                 var pendingInfo = new StreamPendingInfo(pendingMessageCount: (int)arr[0].AsRedisValue(),
                     lowestId: arr[1].AsRedisValue(),
                     highestId: arr[2].AsRedisValue(),
-                    consumers: consumers ?? new StreamConsumer[0]);
+                    consumers: consumers ?? Array.Empty<StreamConsumer>());
                     // ^^^^^
                     // Should we bother allocating an empty array only to prevent the need for a null check?
 
@@ -1744,10 +1742,7 @@ protected NameValueEntry[] ParseStreamEntryValues(RawResult result)
                 // Calculate how many name/value pairs are in the stream entry.
                 int count = arr.Length / 2;
 
-                if (count == 0)
-                {
-                    return new NameValueEntry[0];
-                }
+                if (count == 0) return Array.Empty<NameValueEntry>();
 
                 var pairs = new NameValueEntry[count];
                 int offset = 0;

StackExchange.Redis/StackExchange/Redis/ServerEndPoint.cs

@@ -24,9 +24,8 @@ internal enum UnselectableFlags
     internal sealed partial class ServerEndPoint : IDisposable
     {
         internal volatile ServerEndPoint Master;
-        internal volatile ServerEndPoint[] Slaves = NoSlaves;
+        internal volatile ServerEndPoint[] Slaves = Array.Empty<ServerEndPoint>();
         private static readonly Regex nameSanitizer = new Regex("[^!-~]", RegexOptions.Compiled);
-        private static readonly ServerEndPoint[] NoSlaves = new ServerEndPoint[0];
 
         private readonly Hashtable knownScripts = new Hashtable(StringComparer.Ordinal);
 
@@ -215,7 +214,7 @@ public void SetClusterConfiguration(ClusterConfiguration configuration)
                         }
                     }
                     Master = master;
-                    Slaves = slaves?.ToArray() ?? NoSlaves;
+                    Slaves = slaves?.ToArray() ?? Array.Empty<ServerEndPoint>();
                 }
                 Multiplexer.Trace("Cluster configured");
             }