QueryForNonStaleResults does fine w/ *no* results now. Closes GH-3976

src/EventSourcingTests/Aggregation/querying_with_non_stale_data.cs

@@ -129,6 +129,15 @@ public async Task try_to_query_for_non_stale_data_by_aggregate_type()
         await task;
     }
 
+    [Fact]
+    public async Task cleanly_query_with_no_data()
+    {
+        await theStore.Advanced.ResetAllData();
+
+        var items = await theSession.QueryForNonStaleData<SimpleAggregate>(3.Seconds()).ToListAsync();
+        items.Count.ShouldBe(0);
+    }
+
     public static async Task ExampleUsage()
     {
         #region sample_using_query_for_non_stale_data

src/Marten/Events/AsyncProjectionTestingExtensions.cs

@@ -78,6 +78,9 @@ public static async Task WaitForNonStaleProjectionDataAsync(this IDocumentStore
 
     /// <summary>
     ///     Wait for any running async daemon to catch up to the latest event sequence at the time
+    ///     this is invoked. *Note*, this method was intended for test automation and will wait
+    ///     until there is any event data. If this is not what you intended, use WaitForNonStaleQueryableDataAsync()
+    ///     instead
     /// </summary>
     /// <param name="projectionsCount">
     ///     Will be awaited till all shards have been started before checking if they've caught up
@@ -110,11 +113,46 @@ public static async Task WaitForNonStaleProjectionDataAsync(this IMartenDatabase
             await Task.Delay(100.Milliseconds(), cancellationSource.Token).ConfigureAwait(false);
         } while (true);
 
-        if (initial.EventSequenceNumber == 0)
+        if (initial.EventSequenceNumber == 0 || initial.EventCount == 0)
         {
             throw new TimeoutException("No event activity was detected within the timeout span");
         }
 
+        await database.WaitForNonStaleDataAsync(cancellationSource, projectionsCount, initial).ConfigureAwait(false);
+    }
+
+    /// <summary>
+    /// Wait for all projections and subscriptions to catch up to the high water mark at the point this is called.
+    /// This method will cleanly exit if there is no event data upfront
+    /// </summary>
+    /// <param name="database"></param>
+    /// <param name="timeout"></param>
+    /// <param name="cancellation"></param>
+    public static async Task WaitForNonStaleQueryableDataAsync(this IMartenDatabase database, TimeSpan timeout, CancellationToken cancellation)
+    {
+        // Number of active projection shards, plus the high water mark
+        var projectionsCount = database.As<MartenDatabase>().Options.Projections.AllShards().Count + 1;
+
+        // Just get out of there if there are no projections
+        if (projectionsCount == 1)
+        {
+            return;
+        }
+
+        var initial = await database.FetchEventStoreStatistics(cancellation).ConfigureAwait(false);
+
+        // No data, get out of here
+        if (initial.EventCount == 0 || initial.EventSequenceNumber == 1) return;
+
+        using var cancellationSource = new CancellationTokenSource();
+        cancellationSource.CancelAfter(timeout);
+
+        await database.WaitForNonStaleDataAsync(cancellationSource, projectionsCount, initial).ConfigureAwait(false);
+    }
+
+    public static async Task WaitForNonStaleDataAsync(this IMartenDatabase database, CancellationTokenSource cancellationSource,
+        int projectionsCount, EventStoreStatistics initial)
+    {
         IReadOnlyList<ShardState> projections = [];
         try
         {
@@ -193,6 +231,7 @@ public static async Task WaitForNonStaleProjectionDataAsync(this IMartenDatabase
         }
 
         var highWaterMark = await database.FetchHighestEventSequenceNumber(token).ConfigureAwait(false);
+        if (highWaterMark <= 1) return;
 
         if (tracking.isComplete(highWaterMark)) return;