Merge pull request #453 from DataObjects-NET/7.2-fix-asyncenumerable-disposal

Addresses issue of not disposing IAsyncEnumerator which causes query being open

Author: alex-kulakov

ChangeLog/7.2.1-dev.txt

@@ -1 +1,2 @@
-[main] Added Query.SingleAsync()/SingleOrDefaultAsync and QueryEndpoint.SingleAsync()/SingleOrDefaultAsync methods
+[main] Added Query.SingleAsync()/SingleOrDefaultAsync and QueryEndpoint.SingleAsync()/SingleOrDefaultAsync methods
+[main] Addressed issue of not disposing IAsyncEnumerator which caused query being open

Orm/Xtensive.Orm/Orm/Providers/CommandProcessing/DataReader.cs

@@ -95,7 +95,16 @@ public async ValueTask DisposeAsync()
         await command.DisposeAsync().ConfigureAwait(false);
       }
       else {
-        await ((IAsyncEnumerator<Tuple>) source).DisposeAsync().ConfigureAwait(false);
+        if (source is IAsyncEnumerator<Tuple> asyncSource) {
+          // true async enumerable source
+          await asyncSource.DisposeAsync().ConfigureAwait(false);
+        }
+        else {
+          // preloaded collection of elements,
+          // like in case of delayed query which has already been read from database
+          // or greedy enumeration
+          ((IEnumerator<Tuple>) source).Dispose();
+        }
       }
     }
 

Orm/Xtensive.Orm/Orm/QueryResult.cs

@@ -54,9 +54,10 @@ public IEnumerator<TItem> GetEnumerator()
     public async IAsyncEnumerable<TItem> AsAsyncEnumerable()
     {
       EnsureResultsAlive();
-      var enumerator = reader.AsAsyncEnumerator();
-      while (await enumerator.MoveNextAsync().ConfigureAwait(false)) {
-        yield return enumerator.Current;
+      await using (var enumerator = reader.AsAsyncEnumerator()) {
+        while (await enumerator.MoveNextAsync().ConfigureAwait(false)) {
+          yield return enumerator.Current;
+        }
       }
     }