add missing ReadUnbufferedAsync untyped API (#1958)

* - add missing ReadUnbufferedAsync untyped API
- remove an impossible branch

* release notes

Dapper/PublicAPI/net5.0/PublicAPI.Shipped.txt

@@ -1,5 +1,6 @@
 #nullable enable
 Dapper.SqlMapper.GridReader.DisposeAsync() -> System.Threading.Tasks.ValueTask
+Dapper.SqlMapper.GridReader.ReadUnbufferedAsync() -> System.Collections.Generic.IAsyncEnumerable<dynamic!>!
 Dapper.SqlMapper.GridReader.ReadUnbufferedAsync<T>() -> System.Collections.Generic.IAsyncEnumerable<T>!
 static Dapper.SqlMapper.QueryUnbufferedAsync(this System.Data.Common.DbConnection! cnn, string! sql, object? param = null, System.Data.Common.DbTransaction? transaction = null, int? commandTimeout = null, System.Data.CommandType? commandType = null) -> System.Collections.Generic.IAsyncEnumerable<dynamic!>!
 static Dapper.SqlMapper.QueryUnbufferedAsync<T>(this System.Data.Common.DbConnection! cnn, string! sql, object? param = null, System.Data.Common.DbTransaction? transaction = null, int? commandTimeout = null, System.Data.CommandType? commandType = null) -> System.Collections.Generic.IAsyncEnumerable<T>!

Dapper/SqlMapper.GridReader.Async.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.Data.Common;
-using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Threading;
 using System.Threading.Tasks;
@@ -180,7 +179,6 @@ private Task<IEnumerable<T>> ReadAsyncImpl<T>(Type type, bool buffered)
                 else
                 {
                     var result = ReadDeferred<T>(index, deserializer, type);
-                    if (buffered) result = result.ToList(); // for the "not a DbDataReader" scenario
                     return Task.FromResult(result);
                 }
             }
@@ -256,6 +254,11 @@ private async Task<IEnumerable<T>> ReadBufferedAsync<T>(int index, Func<DbDataRe
             /// <typeparam name="T">The type to read.</typeparam>
             public IAsyncEnumerable<T> ReadUnbufferedAsync<T>() => ReadAsyncUnbufferedImpl<T>(typeof(T));
 
+            /// <summary>
+            /// Read the next grid of results.
+            /// </summary>
+            public IAsyncEnumerable<dynamic> ReadUnbufferedAsync() => ReadAsyncUnbufferedImpl<dynamic>(typeof(DapperRow));
+
             private IAsyncEnumerable<T> ReadAsyncUnbufferedImpl<T>(Type type)
             {
                 var deserializer = ValidateAndMarkConsumed(type, out var index);

docs/index.md

@@ -24,6 +24,8 @@ Note: to get the latest pre-release build, add ` -Pre` to the end of the command
 
 (note: new PRs will not be merged until they add release note wording here)
 
+- add untyped `GridReader.ReadUnbufferedAsync` API (#1958 via @mgravell)
+
 ### 2.1.1
 
 - add NRT annotations (#1928 via @mgravell)

tests/Dapper.Tests/AsyncTests.cs

@@ -112,6 +112,26 @@ public async Task TestBasicStringUsageViaGridReaderUnbufferedAsync()
             Assert.Equal(new[] { "abc", "def", "ghi" }, arr);
         }
 
+        [Fact]
+        public async Task TestBasicStringUsageViaGridReaderUnbufferedDynamicAsync()
+        {
+            var results = new List<string>();
+            await using (var grid = await connection.QueryMultipleAsync("select 'abc' as [Foo] union select 'def'; select @txt as [Foo]", new { txt = "ghi" })
+                .ConfigureAwait(false))
+            {
+                while (!grid.IsConsumed)
+                {
+                    await foreach (var value in grid.ReadUnbufferedAsync()
+                        .ConfigureAwait(false))
+                    {
+                        results.Add((string)value.Foo);
+                    }
+                }
+            }
+            var arr = results.ToArray();
+            Assert.Equal(new[] { "abc", "def", "ghi" }, arr);
+        }
+
         [Fact]
         public async Task TestBasicStringUsageViaGridReaderUnbufferedAsync_Cancellation()
         {