v0.0.437 properly handle $group in wmo extraModPipeline

wmo/collection.go

@@ -125,3 +125,17 @@ func (c *Coll[TData]) createToken(fieldPrimary string, dirPrimary ct.SortDirecti
 		Extra:          ct.Extra{},
 	}, nil
 }
+
+func (c *Coll[TData]) needsDoubleSort(ctx context.Context) bool {
+	for _, ppl := range c.extraModPipeline {
+		for _, stage := range ppl(ctx) {
+			for _, bsone := range stage {
+				if bsone.Key == "$group" {
+					// a group stage in extraModPipeline results in unsorted data, which means the caller must sort again after these pipeline stages...
+					return true
+				}
+			}
+		}
+	}
+	return false
+}