Fix MultiSearchTemplateRequest body (#7008) (#7009)

* Manually define the RequestItem for MultiSearchTemplateRequests

- Manual type implements IStreamSerializable to support NDJSON.
- Add serialization test

* Update integration workflow stack version

* Add release notes

* Make headings discrete

Co-authored-by: Steve Gordon <sgordon@hotmail.co.uk>

Author: github-actions[bot]

.github/workflows/integration-jobs.yml

@@ -26,7 +26,7 @@ jobs:
           '8.2.3',
           '8.3.3',
           '8.4.3',
-          "8.5.0",
+          "8.5.2",
           '8.6.0-SNAPSHOT',
           'latest-8'
         ]

docs/release-notes/release-notes-8.0.1.asciidoc

@@ -0,0 +1,36 @@
+[[release-notes-8.0.1]]
+== Release notes v8.0.1
+
+[discrete]
+=== Bug fixes
+
+- Fix MultiSearchTemplateRequest serialization (issue: 
+https://github.com/elastic/elasticsearch-net/issues/7006[#7006])
+
+[discrete]
+=== Breaking changes
+
+This release includes the following breaking changes:
+
+[discrete]
+==== MultiSearchTemplate type changes
+
+The `Core.MSearchTemplate.RequestItem` type has been renamed to
+`Core.MSearchTemplate.SearchTemplateRequestItem`. It no longer derives from the 
+`Union<T1, T2>` type. It has been manually designed to support serialisation to 
+NDJSON, as required by the MSearchTemplate endpoint.
+
+The `MultiSearchTemplateRequest.SearchTemplates` property has been updated to 
+use this newly defined type.
+
+This breaking change has been included in this patch release due to the 
+original code-generated type not functioning correctly and therefore we have 
+determined that this should ship ASAP.
+
+[discrete]
+=== MultiSearch type changes
+
+The `Core.MSearch.SearchRequestItem` type has been sealed for consistency with 
+the design choices in the rest of the client. While technically breaking, we 
+have decided that this should be included in this release before any potential 
+derived types may exist in consuming applications.

docs/release-notes/release-notes.asciidoc

@@ -2,7 +2,13 @@
 = Release notes
 
 * <<breaking-changes-policy,Breaking changes policy>>
-* <<release-notes-8.0.0,Version 8.0.0>>
+
+[discrete]
+== Version 8.x
+
+* <<release-notes-8.0.0,Release notes v8.0.0>>
+* <<release-notes-8.0.1,Release notes v8.0.1>>
 
 include::breaking-change-policy.asciidoc[]
 include::release-notes-8.0.0.asciidoc[]
+include::release-notes-8.0.1.asciidoc[]

src/Elastic.Clients.Elasticsearch/Types/Documents/MultiSearch/MultiSearchRequest.cs renamed to src/Elastic.Clients.Elasticsearch/Api/MultiSearchRequest.cs

@@ -33,4 +33,7 @@
       <_Parameter1>true</_Parameter1>
     </AssemblyAttribute>
   </ItemGroup>
+  <ItemGroup>
+    <Folder Include="Types\Documents\" />
+  </ItemGroup>
 </Project>

src/Elastic.Clients.Elasticsearch/Elastic.Clients.Elasticsearch.csproj

@@ -11,7 +11,7 @@
 namespace Elastic.Clients.Elasticsearch.Core.MSearch;
 
 // POC - If we have more than one union doing this, can we autogenerate with correct ctors etc.
-public class SearchRequestItem : IStreamSerializable
+public sealed class SearchRequestItem : IStreamSerializable
 {
 	public SearchRequestItem(MultisearchBody body) => Body = body;
 
@@ -52,5 +52,3 @@ async Task IStreamSerializable.SerializeAsync(Stream stream, IElasticsearchClien
 		}
 	}
 }
-
-

src/Elastic.Clients.Elasticsearch/Types/Documents/MultiSearch/SearchRequestItem.cs renamed to src/Elastic.Clients.Elasticsearch/Types/Core/MSearch/SearchRequestItem.cs

@@ -0,0 +1,54 @@
+// Licensed to Elasticsearch B.V under one or more agreements.
+// Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information.
+
+using System.IO;
+using System.Text.Json;
+using System.Threading.Tasks;
+using Elastic.Clients.Elasticsearch.Core.MSearch;
+using Elastic.Clients.Elasticsearch.Serialization;
+using Elastic.Transport;
+
+namespace Elastic.Clients.Elasticsearch.Core.MSearchTemplate;
+
+public sealed class SearchTemplateRequestItem : IStreamSerializable
+{
+	public SearchTemplateRequestItem(TemplateConfig body) => Body = body;
+
+	public SearchTemplateRequestItem(MultisearchHeader header, TemplateConfig body)
+	{
+		Header = header;
+		Body = body;
+	}
+
+	public MultisearchHeader Header { get; init; }
+	public TemplateConfig Body { get; init; }
+
+	void IStreamSerializable.Serialize(Stream stream, IElasticsearchClientSettings settings, SerializationFormatting formatting)
+	{
+		if (Body is null)
+			return;
+
+		if (settings.RequestResponseSerializer.TryGetJsonSerializerOptions(out var options))
+		{
+			JsonSerializer.Serialize(stream, Header, options);
+			stream.WriteByte((byte)'\n');
+			JsonSerializer.Serialize(stream, Body, options);
+			stream.WriteByte((byte)'\n');
+		}
+	}
+
+	async Task IStreamSerializable.SerializeAsync(Stream stream, IElasticsearchClientSettings settings, SerializationFormatting formatting)
+	{
+		if (Body is null)
+			return;
+
+		if (settings.RequestResponseSerializer.TryGetJsonSerializerOptions(out var options))
+		{
+			await JsonSerializer.SerializeAsync(stream, Header, options).ConfigureAwait(false);
+			stream.WriteByte((byte)'\n');
+			await JsonSerializer.SerializeAsync(stream, Body, options).ConfigureAwait(false);
+			stream.WriteByte((byte)'\n');
+		}
+	}
+}

src/Elastic.Clients.Elasticsearch/Types/Core/MSearchTemplate/SearchTemplateRequestItem.cs

@@ -75,7 +75,7 @@ public MultiSearchTemplateRequest(Elastic.Clients.Elasticsearch.Indices? indices
 	[JsonIgnore]
 	public bool? TypedKeys { get => Q<bool?>("typed_keys"); set => Q("typed_keys", value); }
 
-	public List<Core.MSearchTemplate.RequestItem> SearchTemplates { get; set; }
+	public List<Core.MSearchTemplate.SearchTemplateRequestItem> SearchTemplates { get; set; }
 
 	void IStreamSerializable.Serialize(Stream stream, IElasticsearchClientSettings settings, SerializationFormatting formatting)
 	{
@@ -125,7 +125,7 @@ protected override void Serialize(Utf8JsonWriter writer, JsonSerializerOptions o
 	{
 	}
 
-	List<Core.MSearchTemplate.RequestItem> _items = new();
+	List<Core.MSearchTemplate.SearchTemplateRequestItem> _items = new();
 	void IStreamSerializable.Serialize(Stream stream, IElasticsearchClientSettings settings, SerializationFormatting formatting)
 	{
 		if (_items is null)
@@ -148,7 +148,7 @@ async Task IStreamSerializable.SerializeAsync(Stream stream, IElasticsearchClien
 		}
 	}
 
-	public MultiSearchTemplateRequestDescriptor<TDocument> Add(Core.MSearchTemplate.RequestItem item)
+	public MultiSearchTemplateRequestDescriptor<TDocument> Add(Core.MSearchTemplate.SearchTemplateRequestItem item)
 	{
 		_items.Add(item);
 		return this;
@@ -180,7 +180,7 @@ protected override void Serialize(Utf8JsonWriter writer, JsonSerializerOptions o
 	{
 	}
 
-	List<Core.MSearchTemplate.RequestItem> _items = new();
+	List<Core.MSearchTemplate.SearchTemplateRequestItem> _items = new();
 	void IStreamSerializable.Serialize(Stream stream, IElasticsearchClientSettings settings, SerializationFormatting formatting)
 	{
 		if (_items is null)
@@ -203,7 +203,7 @@ async Task IStreamSerializable.SerializeAsync(Stream stream, IElasticsearchClien
 		}
 	}
 
-	public MultiSearchTemplateRequestDescriptor Add(Core.MSearchTemplate.RequestItem item)
+	public MultiSearchTemplateRequestDescriptor Add(Core.MSearchTemplate.SearchTemplateRequestItem item)
 	{
 		_items.Add(item);
 		return this;

src/Elastic.Clients.Elasticsearch/_Generated/Api/MultiSearchTemplateRequest.g.cs

@@ -0,0 +1,69 @@
+// Licensed to Elasticsearch B.V under one or more agreements.
+// Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.IO;
+using System.Threading.Tasks;
+using Elastic.Clients.Elasticsearch.Core.MSearch;
+using Elastic.Clients.Elasticsearch.Core.MSearchTemplate;
+using Elastic.Clients.Elasticsearch.Serialization;
+using Tests.Domain;
+using VerifyTests;
+using VerifyXunit;
+
+namespace Tests.Core.MSearchTemplate;
+
+[UsesVerify]
+public class MSearchTemplateSerialization
+{
+	private readonly VerifySettings _verifySettings;
+
+	public MSearchTemplateSerialization()
+	{
+		_verifySettings = new VerifySettings();
+		_verifySettings.DisableRequireUniquePrefix();
+	}
+
+	[U]
+	public async Task SerializesMultiSearchTemplateRequest()
+	{
+		var settings = new ElasticsearchClientSettings();
+		settings.DefaultMappingFor<Project>(m => m.IndexName("projects"));
+
+		var ms = new MemoryStream();
+
+		var request = (IStreamSerializable)new MultiSearchTemplateRequest
+		{
+			SearchTemplates = new List<SearchTemplateRequestItem>
+			{
+				new SearchTemplateRequestItem(new MultisearchHeader { Index = Infer.Index<Project>() }, new TemplateConfig { Id = "my-search-template", Params = new Dictionary<string, object>
+				{
+					{ "query_string", "hello world" },
+					{ "from", 0 }
+				}}),
+				new SearchTemplateRequestItem(new MultisearchHeader { Index = Infer.Index<Project>() }, new TemplateConfig { Id = "my-search-template", Params = new Dictionary<string, object>
+				{
+					{ "query_type", "match_all" }
+				}}),
+			}
+		};
+
+		await request.SerializeAsync(ms, settings);
+
+		ms.Position = 0;
+		var reader = new StreamReader(ms);
+		var ndjson = reader.ReadToEnd();
+
+		await Verifier.Verify(ndjson, _verifySettings);
+
+		ms = new MemoryStream();
+		request.Serialize(ms, settings);
+
+		ms.Position = 0;
+		reader = new StreamReader(ms);
+		ndjson = reader.ReadToEnd();
+
+		await Verifier.Verify(ndjson, _verifySettings);
+	}
+}