support reading from last message from stream with xread (#2725)

* support reading from last message from stream with xread

* recover previous formatting

* add redisversion and use it in integration tests

Author: atakavci

src/StackExchange.Redis/RedisFeatures.cs

@@ -40,7 +40,8 @@ namespace StackExchange.Redis
                                          v6_0_6 = new Version(6, 0, 6),
                                          v6_2_0 = new Version(6, 2, 0),
                                          v7_0_0_rc1 = new Version(6, 9, 240), // 7.0 RC1 is version 6.9.240
-                                         v7_2_0_rc1 = new Version(7, 1, 240); // 7.2 RC1 is version 7.1.240
+                                         v7_2_0_rc1 = new Version(7, 1, 240), // 7.2 RC1 is version 7.1.240
+                                         v7_4_0_rc1 = new Version(7, 4, 240); // 7.4 RC1 is version 7.4.240
 
         private readonly Version version;
 

tests/StackExchange.Redis.Tests/StreamTests.cs

@@ -1511,6 +1511,24 @@ public void StreamReadEmptyStreams()
         Assert.Equal(0, len2);
     }
 
+    [Fact]
+    public void StreamReadLastMessage()
+    {
+        using var conn = Create(require: RedisFeatures.v7_4_0_rc1);
+        var db = conn.GetDatabase();
+        var key1 = Me();
+
+        // Read the entire stream from the beginning.
+        db.StreamRead(key1, "0-0");
+        db.StreamAdd(key1, "field2", "value2");
+        db.StreamAdd(key1, "fieldLast", "valueLast");
+        var entries = db.StreamRead(key1, "+");
+
+        Assert.NotNull(entries);
+        Assert.True(entries.Length > 0);
+        Assert.Equal(new[] { new NameValueEntry("fieldLast", "valueLast") }, entries[0].Values);
+    }
+
     [Fact]
     public void StreamReadExpectedExceptionInvalidCountMultipleStream()
     {
@@ -1590,6 +1608,49 @@ public void StreamReadMultipleStreams()
         Assert.Equal(id4, streams[1].Entries[1].Id);
     }
 
+    [Fact]
+    public void StreamReadMultipleStreamsLastMessage()
+    {
+        using var conn = Create(require: RedisFeatures.v7_4_0_rc1);
+
+        var db = conn.GetDatabase();
+        var key1 = Me() + "a";
+        var key2 = Me() + "b";
+
+        var id1 = db.StreamAdd(key1, "field1", "value1");
+        var id2 = db.StreamAdd(key1, "field2", "value2");
+        var id3 = db.StreamAdd(key2, "field3", "value3");
+        var id4 = db.StreamAdd(key2, "field4", "value4");
+
+        var streamList = new[] { new StreamPosition(key1, "0-0"), new StreamPosition(key2, "0-0") };
+        db.StreamRead(streamList);
+
+        var streams = db.StreamRead(streamList);
+
+        db.StreamAdd(key1, "field5", "value5");
+        db.StreamAdd(key1, "field6", "value6");
+        db.StreamAdd(key2, "field7", "value7");
+        db.StreamAdd(key2, "field8", "value8");
+
+        streamList = new[] { new StreamPosition(key1, "+"), new StreamPosition(key2, "+") };
+
+        streams = db.StreamRead(streamList);
+
+        Assert.NotNull(streams);
+        Assert.True(streams.Length == 2);
+
+        var stream1 = streams.Where(e => e.Key == key1).First();
+        Assert.NotNull(stream1.Entries);
+        Assert.True(stream1.Entries.Length > 0);
+        Assert.Equal(new[] { new NameValueEntry("field6", "value6") }, stream1.Entries[0].Values);
+
+        var stream2 = streams.Where(e => e.Key == key2).First();
+        Assert.NotNull(stream2.Entries);
+        Assert.True(stream2.Entries.Length > 0);
+        Assert.Equal(new[] { new NameValueEntry("field8", "value8") }, stream2.Entries[0].Values);
+    }
+
+
     [Fact]
     public void StreamReadMultipleStreamsWithCount()
     {