GH-3530: Add a mechanism to Drivers to execute a command and return a DbDataReader.

Author: David Ellingsworth

src/NHibernate/AdoNet/AbstractBatcher.cs

@@ -252,7 +252,7 @@ private DbDataReader DoExecuteReader(DbCommand cmd)
 		{
 			try
 			{
-				var reader = cmd.ExecuteReader();
+				var reader = Driver.ExecuteReader(cmd);
 				if (reader == null)
 				{
 					// MySql may return null instead of an exception, by example when the query is canceled by another thread.

src/NHibernate/Async/AdoNet/AbstractBatcher.cs

@@ -167,7 +167,7 @@ private async Task<DbDataReader> DoExecuteReaderAsync(DbCommand cmd, Cancellatio
 			cancellationToken.ThrowIfCancellationRequested();
 			try
 			{
-				var reader = await (cmd.ExecuteReaderAsync(cancellationToken)).ConfigureAwait(false);
+				var reader = await (Driver.ExecuteReaderAsync(cmd, cancellationToken)).ConfigureAwait(false);
 				if (reader == null)
 				{
 					// MySql may return null instead of an exception, by example when the query is canceled by another thread.

src/NHibernate/Async/Driver/DriverBase.cs

@@ -0,0 +1,44 @@
+//------------------------------------------------------------------------------
+// <auto-generated>
+//     This code was generated by AsyncGenerator.
+//
+//     Changes to this file may cause incorrect behavior and will be lost if
+//     the code is regenerated.
+// </auto-generated>
+//------------------------------------------------------------------------------
+
+
+using System;
+using System.Collections.Generic;
+using System.Data;
+using System.Data.Common;
+using System.Linq;
+using NHibernate.Engine;
+using NHibernate.SqlCommand;
+using NHibernate.SqlTypes;
+using NHibernate.Util;
+using Environment = NHibernate.Cfg.Environment;
+
+namespace NHibernate.Driver
+{
+	using System.Threading.Tasks;
+	using System.Threading;
+	public abstract partial class DriverBase : IDriver, ISqlParameterFormatter
+	{
+
+		#if NETFX
+		#else
+
+		#endif
+
+		/// <inheritdoc />
+		public virtual Task<DbDataReader> ExecuteReaderAsync(DbCommand command, CancellationToken cancellationToken)
+		{
+			if (cancellationToken.IsCancellationRequested)
+			{
+				return Task.FromCanceled<DbDataReader>(cancellationToken);
+			}
+			return command.ExecuteReaderAsync(cancellationToken);
+		}
+	}
+}

src/NHibernate/Async/Driver/DriverExtensions.cs

@@ -0,0 +1,49 @@
+//------------------------------------------------------------------------------
+// <auto-generated>
+//     This code was generated by AsyncGenerator.
+//
+//     Changes to this file may cause incorrect behavior and will be lost if
+//     the code is regenerated.
+// </auto-generated>
+//------------------------------------------------------------------------------
+
+
+using System.Data;
+using System.Data.Common;
+using NHibernate.AdoNet;
+using NHibernate.SqlTypes;
+using NHibernate.Util;
+
+namespace NHibernate.Driver
+{
+	using System.Threading.Tasks;
+	using System.Threading;
+	public static partial class DriverExtensions
+	{
+
+		// 6.0 TODO: merge into IDriver
+		/// <summary>
+		/// Executes the command and returns a <see cref="DbDataReader"/>.
+		/// </summary>
+		/// <param name="driver">The driver.</param>
+		/// <param name="command">The command to execute.</param>
+		/// <param name="cancellationToken">A cancellation token that can be used to cancel the work</param>
+		/// <returns>A DbDataReader</returns>
+		public static Task<DbDataReader> ExecuteReaderAsync(this IDriver driver, DbCommand command, CancellationToken cancellationToken)
+		{
+			if (cancellationToken.IsCancellationRequested)
+			{
+				return Task.FromCanceled<DbDataReader>(cancellationToken);
+			}
+			try
+			{
+				return driver is DriverBase driverBase ? driverBase.ExecuteReaderAsync(command, cancellationToken) : command.ExecuteReaderAsync(cancellationToken);
+			}
+			catch (System.Exception ex)
+			{
+				return Task.FromException<DbDataReader>(ex);
+			}
+		}
+
+	}
+}

src/NHibernate/Driver/DriverBase.cs

@@ -14,7 +14,7 @@ namespace NHibernate.Driver
 	/// <summary>
 	/// Base class for the implementation of IDriver
 	/// </summary>
-	public abstract class DriverBase : IDriver, ISqlParameterFormatter
+	public abstract partial class DriverBase : IDriver, ISqlParameterFormatter
 	{
 		private static readonly INHibernateLogger log = NHibernateLogger.For(typeof(DriverBase));
 
@@ -361,5 +361,11 @@ public DbParameter GenerateOutputParameter(DbCommand command)
 		/// Get the timeout in seconds for ADO.NET queries.
 		/// </summary>
 		public virtual int CommandTimeout => commandTimeout;
+
+		/// <inheritdoc />
+		public virtual DbDataReader ExecuteReader(DbCommand command)
+		{
+			return command.ExecuteReader();
+		}
 	}
 }

src/NHibernate/Driver/DriverExtensions.cs

@@ -6,7 +6,7 @@
 
 namespace NHibernate.Driver
 {
-	public static class DriverExtensions
+	public static partial class DriverExtensions
 	{
 		internal static void AdjustParameterForValue(this IDriver driver, DbParameter parameter, SqlType sqlType, object value)
 		{
@@ -60,5 +60,18 @@ public static DbCommand UnwrapDbCommand(this IDriver driver, DbCommand command)
 		{
 			return driver is DriverBase driverBase ? driverBase.UnwrapDbCommand(command) : command;
 		}
+
+		// 6.0 TODO: merge into IDriver
+		/// <summary>
+		/// Executes the command and returns a <see cref="DbDataReader"/>.
+		/// </summary>
+		/// <param name="driver">The driver.</param>
+		/// <param name="command">The command to execute.</param>
+		/// <returns>A DbDataReader</returns>
+		public static DbDataReader ExecuteReader(this IDriver driver, DbCommand command)
+		{
+			return driver is DriverBase driverBase ? driverBase.ExecuteReader(command) : command.ExecuteReader();
+		}
+
 	}
 }