Report empty GridReader results as consumed

Dapper/SqlMapper.GridReader.cs

@@ -417,7 +417,35 @@ private IEnumerable<T> ReadDeferred<T>(int index, Func<DbDataReader, object> des
             /// Has the underlying reader been consumed?
             /// </summary>
             /// <remarks>This also reports <c>true</c> if the current grid is actively being consumed</remarks>
-            public bool IsConsumed => (_resultIndexAndConsumedFlag & CONSUMED_FLAG) != 0;
+            public bool IsConsumed
+            {
+                get
+                {
+                    SkipLeadingEmptyResults();
+                    return (_resultIndexAndConsumedFlag & CONSUMED_FLAG) != 0;
+                }
+            }
+
+            private bool _checkedLeadingResults;
+
+            // A reader positioned on a result without columns (for example a procedure that
+            // selects in a loop which never iterated) has nothing to read. Skip such results; only
+            // when no further result exists is the grid consumed. A zero-column result followed by a
+            // real result set must not be reported as consumed.
+            private void SkipLeadingEmptyResults()
+            {
+                if (_checkedLeadingResults) return;
+                _checkedLeadingResults = true;
+                if (reader is null || reader.IsClosed || _resultIndexAndConsumedFlag != 0) return;
+                while (reader.FieldCount == 0)
+                {
+                    if (!reader.NextResult())
+                    {
+                        _resultIndexAndConsumedFlag |= CONSUMED_FLAG;
+                        return;
+                    }
+                }
+            }
 
             /// <summary>
             /// The command associated with the reader

Directory.Packages.props

@@ -35,6 +35,7 @@
     <PackageVersion Include="Norm.net" Version="5.4.0" />
     <PackageVersion Include="Npgsql" Version="10.0.2" />
     <PackageVersion Include="PetaPoco" Version="5.1.306" />
+    <PackageVersion Include="pengdows.crud.fakeDb" Version="2.0.5" />
     <PackageVersion Include="RepoDb.SqlServer" Version="1.13.1" />
     <PackageVersion Include="ServiceStack.OrmLite.SqlServer" Version="10.0.6" />
     <PackageVersion Include="Snowflake.Data" Version="5.5.0" />

tests/Dapper.Tests/Dapper.Tests.csproj

@@ -31,8 +31,9 @@
     <PackageReference Include="log4net" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetFramework)' != 'net481'">
-    <PackageReference Include="Npgsql" />
+  <ItemGroup Condition="'$(TargetFramework)' != 'net481'">
+    <PackageReference Include="pengdows.crud.fakeDb" />
+    <PackageReference Include="Npgsql" />
     <PackageReference Include="Snowflake.Data" />
   </ItemGroup>
 

tests/Dapper.Tests/FakeDbTests.Issue751.cs

@@ -0,0 +1,61 @@
+#if !NET481
+using System.Collections.Generic;
+using System.Linq;
+using pengdows.crud.fakeDb;
+using Xunit;
+
+namespace Dapper.Tests
+{
+    public sealed class FakeDbIssue751Tests
+    {
+        [Fact]
+        public void IsConsumedIsTrueWhenReaderHasNoResultSets()
+        {
+            using var conn = new fakeDbConnection(new FakeDataStore());
+            conn.Open();
+
+            using var grid = conn.QueryMultiple("exec NoResultSets");
+
+            Assert.True(grid.IsConsumed);
+        }
+
+        [Fact]
+        public void IsConsumedIsFalseWhenEmptyResultPrecedesRealResultSet()
+        {
+            using var conn = new fakeDbConnection(new FakeDataStore());
+            conn.EnqueueMultiResultReader(new[]
+            {
+                Enumerable.Empty<Dictionary<string, object?>>(),
+                new[] { new Dictionary<string, object?> { ["Value"] = 7 } }
+            });
+            conn.Open();
+
+            using var grid = conn.QueryMultiple("insert x; select 7");
+
+            Assert.False(grid.IsConsumed);
+            Assert.Equal(7, grid.Read<int>().Single());
+            Assert.True(grid.IsConsumed);
+        }
+
+        [Fact]
+        public void IsConsumedIsFalseForNonEmptyFirstResultAndTrueAfterLast()
+        {
+            using var conn = new fakeDbConnection(new FakeDataStore());
+            conn.EnqueueMultiResultReader(new[]
+            {
+                new[] { new Dictionary<string, object?> { ["Value"] = 1 } },
+                new[] { new Dictionary<string, object?> { ["Value"] = 2 } }
+            });
+            conn.Open();
+
+            using var grid = conn.QueryMultiple("select 1; select 2");
+
+            Assert.False(grid.IsConsumed);
+            Assert.Equal(1, grid.Read<int>().Single());
+            Assert.False(grid.IsConsumed);
+            Assert.Equal(2, grid.Read<int>().Single());
+            Assert.True(grid.IsConsumed);
+        }
+    }
+}
+#endif