[Backport 7.6] Fix GetMany when no default index is set

src/Nest/Document/Multiple/Bulk/ElasticClient-DeleteMany.cs

@@ -6,7 +6,7 @@
 namespace Nest
 {
 	/// <summary>
-	/// Provides GetMany extensions that make it easier to get many documents given a list of ids
+	/// Provides DeleteMany extensions that make it easier to get many documents given a list of ids
 	/// </summary>
 	public static class DeleteManyExtensions
 	{

src/Nest/Document/Multiple/MultiGet/ElasticClient-GetMany.cs

@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
 using System.Threading;
@@ -11,6 +12,14 @@ namespace Nest
 	/// </summary>
 	public static class GetManyExtensions
 	{
+		private static Func<MultiGetOperationDescriptor<T>, string, IMultiGetOperation> Lookup<T>(IndexName index)
+			where T : class
+		{
+			if (index == null) return null;
+
+			return (d, id) => d.Index(index);
+		}
+
 		/// <summary>
 		/// Multi GET API allows to get multiple documents based on an index, type (optional) and id (and possibly routing).
 		/// The response includes a docs array with all the fetched documents, each element similar in structure to a document
@@ -29,7 +38,7 @@ public static IEnumerable<IMultiGetHit<T>> GetMany<T>(this IElasticClient client
 			var result = client.MultiGet(s => s
 				.Index(index)
 				.RequestConfiguration(r => r.ThrowExceptions())
-				.GetMany<T>(ids)
+				.GetMany<T>(ids, Lookup<T>(index))
 			);
 			return result.GetMany<T>(ids);
 		}
@@ -68,7 +77,7 @@ public static async Task<IEnumerable<IMultiGetHit<T>>> GetManyAsync<T>(
 			var response = await client.MultiGetAsync(s => s
 						.Index(index)
 						.RequestConfiguration(r => r.ThrowExceptions())
-						.GetMany<T>(ids),
+						.GetMany<T>(ids, Lookup<T>(index)),
 					cancellationToken
 				)
 				.ConfigureAwait(false);

src/Nest/Document/Multiple/MultiGet/ElasticClient-SourceMany.cs

@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
 using System.Threading;
@@ -11,6 +12,15 @@ namespace Nest
 	/// </summary>
 	public static class SourceManyExtensions
 	{
+
+		private static Func<MultiGetOperationDescriptor<T>, string, IMultiGetOperation> Lookup<T>(IndexName index)
+			where T : class
+		{
+			if (index == null) return null;
+
+			return (d, id) => d.Index(index);
+		}
+
 		/// <summary>
 		/// SourceMany allows you to get a list of T documents out of Elasticsearch, internally it calls into MultiGet()
 		/// <para>
@@ -31,7 +41,7 @@ public static IEnumerable<T> SourceMany<T>(this IElasticClient client, IEnumerab
 			var result = client.MultiGet(s => s
 				.Index(index)
 				.RequestConfiguration(r => r.ThrowExceptions())
-				.GetMany<T>(ids, (gs, i) => gs )
+				.GetMany<T>(ids, Lookup<T>(index))
 			);
 			return result.SourceMany<T>(ids);
 		}
@@ -75,7 +85,7 @@ public static async Task<IEnumerable<T>> SourceManyAsync<T>(
 			var response = await client.MultiGetAsync(s => s
 					.Index(index)
 					.RequestConfiguration(r => r.ThrowExceptions())
-					.GetMany<T>(ids, (gs, i) => gs), cancellationToken)
+					.GetMany<T>(ids, Lookup<T>(index)), cancellationToken)
 				.ConfigureAwait(false);
 			return response.SourceMany<T>(ids);
 		}

tests/Tests.Reproduce/GitHubIssue4462.cs

@@ -0,0 +1,53 @@
+using System;
+using System.Text;
+using Elastic.Xunit.XunitPlumbing;
+using Elasticsearch.Net;
+using FluentAssertions;
+using Nest;
+using Tests.Domain;
+
+namespace Tests.Reproduce
+{
+	/*
+	 * https://github.com/elastic/elasticsearch-net/pull/4353
+	 * Fixed an issue with the GetMany helpers that returned the cartesian product of all ids specified rather
+	 * then creating a distinct list if more then one index was targeted.
+	 *
+	 * This PR also updated the routine in the serializer to omit the index name from each item if the index is
+	 * already specified on the url in case of multiple indices
+	 *
+	 * This updated routine in the `7.6.0` could throw if you are calling:
+	 *
+	 * client.GetMany<T>(ids, "indexName");
+	 *
+	 * Without configuring `ConnectionSettings()` with either a default index for T or a global default index.
+	 */
+	public class GitHubIssue4462
+	{
+		[U] public void GetManyShouldNotThrowIfIndexIsProvided()
+		{
+			var json = "{}";
+
+			var bytes = Encoding.UTF8.GetBytes(json);
+			var pool = new SingleNodeConnectionPool(new Uri("http://localhost:9200"));
+			var connectionSettings = new ConnectionSettings(pool, new InMemoryConnection(bytes));
+			var client = new ElasticClient(connectionSettings);
+
+			var response = client.GetMany<Project>(new long[] {1, 2, 3}, "indexName");
+			response.Should().NotBeNull();
+		}
+
+		[U] public void SourceManyShouldNotThrowIfIndexIsProvided()
+		{
+			var json = "{}";
+
+			var bytes = Encoding.UTF8.GetBytes(json);
+			var pool = new SingleNodeConnectionPool(new Uri("http://localhost:9200"));
+			var connectionSettings = new ConnectionSettings(pool, new InMemoryConnection(bytes));
+			var client = new ElasticClient(connectionSettings);
+
+			var response = client.SourceMany<Project>(new long[] {1, 2, 3}, "indexName");
+			response.Should().NotBeNull();
+		}
+	}
+}