Make sure the initial cursor/pageOffset are correct (for both enumerable and...

Make sure the initial cursor/pageOffset are correct (for both enumerable and enumerator) even if not iterated

StackExchange.Redis.Tests/Scans.cs

@@ -99,7 +99,7 @@ public void ScanResume()
                 
                 var expected = new HashSet<string>();
                 long snapCursor = 0;
-                int snapOffset = 0;
+                int snapOffset = 0, snapPageSize = 0;
 
                 i = 0;
                 var seq = server.Keys(DB, pageSize: 15);
@@ -111,14 +111,41 @@ public void ScanResume()
                     {
                         snapCursor = ((IScanningCursor)seq).Cursor;
                         snapOffset = ((IScanningCursor)seq).PageOffset;
+                        snapPageSize = ((IScanningCursor)seq).PageSize;
                     }
                     expected.Add((string)key);
                 }                
                 Assert.AreNotEqual(43, expected.Count);
                 Assert.AreNotEqual(0, snapCursor);
                 Assert.AreEqual(11, snapOffset);
+                Assert.AreEqual(15, snapPageSize);
 
                 seq = server.Keys(DB, pageSize: 15, cursor: snapCursor, pageOffset: snapOffset);
+                var seqCur = (IScanningCursor)seq;
+                Assert.AreEqual(snapCursor, seqCur.Cursor);
+                Assert.AreEqual(snapPageSize, seqCur.PageSize);
+                Assert.AreEqual(snapOffset, seqCur.PageOffset);
+                using(var iter = seq.GetEnumerator())
+                {
+                    var iterCur = (IScanningCursor)iter;
+                    Assert.AreEqual(snapCursor, iterCur.Cursor);
+                    Assert.AreEqual(snapOffset, iterCur.PageOffset);
+                    Assert.AreEqual(snapCursor, seqCur.Cursor);
+                    Assert.AreEqual(snapOffset, seqCur.PageOffset);
+
+                    Assert.IsTrue(iter.MoveNext());
+                    Assert.AreEqual(snapCursor, iterCur.Cursor);
+                    Assert.AreEqual(snapOffset, iterCur.PageOffset);
+                    Assert.AreEqual(snapCursor, seqCur.Cursor);
+                    Assert.AreEqual(snapOffset, seqCur.PageOffset);
+
+                    Assert.IsTrue(iter.MoveNext());
+                    Assert.AreEqual(snapCursor, iterCur.Cursor);
+                    Assert.AreEqual(snapOffset + 1, iterCur.PageOffset);
+                    Assert.AreEqual(snapCursor, seqCur.Cursor);
+                    Assert.AreEqual(snapOffset + 1, seqCur.PageOffset);
+                }
+
                 int count = 0;
                 foreach(var key in seq)
                 {

StackExchange.Redis/StackExchange/Redis/RedisBase.cs

@@ -164,6 +164,7 @@ internal abstract class CursorEnumerable<T> : IEnumerable<T>, IScanningCursor
 
             protected CursorEnumerable(RedisBase redis, ServerEndPoint server, int db, int pageSize, long cursor, int pageOffset, CommandFlags flags)
             {
+                if (pageOffset < 0) throw new ArgumentOutOfRangeException("pageOffset");
                 this.redis = redis;
                 this.server = server;
                 this.db = db;
@@ -281,7 +282,7 @@ public bool MoveNext()
                             return false;
                         case State.Initial:
                             ProcessReply(parent.GetNextPageSync(this, nextCursor));
-                            pageIndex = parent.initialOffset - 1;
+                            pageIndex = parent.initialOffset - 1; // will be incremented in a moment
                             state = State.Running;
                             LoadNextPageAsync();
                             goto case State.Running;
@@ -316,7 +317,7 @@ public void Reset()
                 {
                     if(state == State.Disposed) throw new ObjectDisposedException(GetType().Name);
                     nextCursor = currentCursor = parent.initialCursor;
-                    pageIndex = parent.initialOffset - 1;
+                    pageIndex = parent.initialOffset; // don't -1 here; this makes it look "right" before incremented
                     state = State.Initial;
                     page = null;                    
                     pending = null;
@@ -340,7 +341,7 @@ int IScanningCursor.PageOffset
 
             long IScanningCursor.Cursor
             {
-                get { var tmp = activeCursor; return tmp == null ? CursorUtils.Origin : tmp.Cursor; }
+                get { var tmp = activeCursor; return tmp == null ? initialCursor : tmp.Cursor; }
             }
 
             int IScanningCursor.PageSize
@@ -349,7 +350,7 @@ int IScanningCursor.PageSize
             }
             int IScanningCursor.PageOffset
             {
-                get { var tmp = activeCursor; return tmp == null ? 0 : tmp.PageOffset; }
+                get { var tmp = activeCursor; return tmp == null ? initialOffset : tmp.PageOffset; }
             }
         }
     }