Fix code-gen for single or many types.

src/Elastic.Clients.Elasticsearch/Serialization/DefaultRequestResponseSerializer.cs

@@ -52,7 +52,8 @@ public DefaultRequestResponseSerializer(IElasticsearchClientSettings settings)
 					new ExtraSerializationData(settings),
 					new DictionaryResponseConverterFactory(settings)
 				},
-			PropertyNamingPolicy = JsonNamingPolicy.CamelCase
+			PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+			NumberHandling = JsonNumberHandling.AllowReadingFromString | JsonNumberHandling.AllowNamedFloatingPointLiterals
 		};
 
 		ElasticsearchClient.SettingsTable.Add(Options, settings);

src/Elastic.Clients.Elasticsearch/Serialization/DefaultSourceSerializer.cs

@@ -24,6 +24,7 @@ public DefaultSourceSerializer(IElasticsearchClientSettings settings, JsonSerial
 					new LazyJsonConverter(settings),
 					new IdsConverter(settings)
 			},
-			PropertyNamingPolicy = JsonNamingPolicy.CamelCase
+			PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+			NumberHandling = JsonNumberHandling.AllowReadingFromString | JsonNumberHandling.AllowNamedFloatingPointLiterals
 		};
 }

src/Elastic.Clients.Elasticsearch/Serialization/SingleOrManyCollectionAttribute.cs

@@ -0,0 +1,18 @@
+// 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;
+using System.Text.Json.Serialization;
+
+namespace Elastic.Clients.Elasticsearch.Serialization;
+
+[AttributeUsage(AttributeTargets.Property)]
+internal class SingleOrManyCollectionConverterAttribute : JsonConverterAttribute
+{
+	public SingleOrManyCollectionConverterAttribute(Type convertType) => ConvertType = convertType;
+
+	public Type ConvertType { get; }
+
+	public override JsonConverter? CreateConverter(Type typeToConvert) => (JsonConverter)Activator.CreateInstance(typeof(SingleOrManyCollectionConverter<>).MakeGenericType(ConvertType));
+}

src/Elastic.Clients.Elasticsearch/Serialization/IEnumerableSingleOrManyConverter.cs → src/Elastic.Clients.Elasticsearch/Serialization/SingleOrManyCollectionConverter.cs

@@ -9,7 +9,7 @@
 
 namespace Elastic.Clients.Elasticsearch.Serialization;
 
-internal abstract class ICollectionSingleOrManyConverter<TItem> : JsonConverter<ICollection<TItem>>
+internal class SingleOrManyCollectionConverter<TItem> : JsonConverter<ICollection<TItem>>
 {
 	public override ICollection<TItem>? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options) =>
 		SingleOrManySerializationHelper.Deserialize<TItem>(ref reader, options);

src/Elastic.Clients.Elasticsearch/Serialization/UnionConverter.cs

@@ -147,7 +147,49 @@ public override void Write(Utf8JsonWriter writer, TType value,
 	private class UnionConverterInner<TItem1, TItem2> : JsonConverter<Union<TItem1, TItem2>>
 	{
 		public override Union<TItem1, TItem2>? Read(ref Utf8JsonReader reader, Type typeToConvert,
-			JsonSerializerOptions options) => null;
+			JsonSerializerOptions options)
+		{
+			var readerCopy = reader;
+
+			try
+			{
+				var itemOne = JsonSerializer.Deserialize<TItem1>(ref readerCopy, options);
+
+				if (itemOne is IUnionVerifiable verifiable)
+				{
+					if (verifiable.IsSuccessful)
+					{
+						reader = readerCopy;
+						return (TItem1)Activator.CreateInstance(typeof(TItem1), itemOne);
+					}
+				}
+				else if (itemOne is not null)
+				{
+					reader = readerCopy;
+					return (TItem1)Activator.CreateInstance(typeof(TItem1), itemOne);
+				}
+			}
+			catch
+			{
+				// TODO - Store for aggregate exception
+			}
+
+			try
+			{
+				var itemTwo = JsonSerializer.Deserialize<TItem2>(ref reader, options);
+
+				if (itemTwo is not null)
+				{
+					return (TItem2)Activator.CreateInstance(typeof(TItem2), itemTwo);
+				}
+			}
+			catch
+			{
+				// TODO - Store for aggregate exception
+			}
+
+			throw new JsonException("Unable to deserialize union."); // TODO - Add inner aggregate exception.
+		}
 
 		public override void Write(Utf8JsonWriter writer, Union<TItem1, TItem2> value,
 			JsonSerializerOptions options)

src/Elastic.Clients.Elasticsearch/_Generated/Api/AsyncSearch/AsyncSearchStatusResponse.g.cs

@@ -26,39 +26,30 @@
 namespace Elastic.Clients.Elasticsearch.AsyncSearch;
 public sealed partial class AsyncSearchStatusResponse : ElasticsearchResponse
 {
-	[JsonInclude]
-	[JsonPropertyName("completion_status")]
+	[JsonInclude, JsonPropertyName("completion_status")]
 	public int? CompletionStatus { get; init; }
 
-	[JsonInclude]
-	[JsonPropertyName("expiration_time")]
+	[JsonInclude, JsonPropertyName("expiration_time")]
 	public DateTimeOffset? ExpirationTime { get; init; }
 
-	[JsonInclude]
-	[JsonPropertyName("expiration_time_in_millis")]
+	[JsonInclude, JsonPropertyName("expiration_time_in_millis")]
 	public long ExpirationTimeInMillis { get; init; }
 
-	[JsonInclude]
-	[JsonPropertyName("id")]
+	[JsonInclude, JsonPropertyName("id")]
 	public string? Id { get; init; }
 
-	[JsonInclude]
-	[JsonPropertyName("is_partial")]
+	[JsonInclude, JsonPropertyName("is_partial")]
 	public bool IsPartial { get; init; }
 
-	[JsonInclude]
-	[JsonPropertyName("is_running")]
+	[JsonInclude, JsonPropertyName("is_running")]
 	public bool IsRunning { get; init; }
 
-	[JsonInclude]
-	[JsonPropertyName("_shards")]
+	[JsonInclude, JsonPropertyName("_shards")]
 	public Elastic.Clients.Elasticsearch.ShardStatistics Shards { get; init; }
 
-	[JsonInclude]
-	[JsonPropertyName("start_time")]
+	[JsonInclude, JsonPropertyName("start_time")]
 	public DateTimeOffset? StartTime { get; init; }
 
-	[JsonInclude]
-	[JsonPropertyName("start_time_in_millis")]
+	[JsonInclude, JsonPropertyName("start_time_in_millis")]
 	public long StartTimeInMillis { get; init; }
 }

src/Elastic.Clients.Elasticsearch/_Generated/Api/AsyncSearch/DeleteAsyncSearchResponse.g.cs

@@ -25,7 +25,6 @@
 namespace Elastic.Clients.Elasticsearch.AsyncSearch;
 public sealed partial class DeleteAsyncSearchResponse : ElasticsearchResponse
 {
-	[JsonInclude]
-	[JsonPropertyName("acknowledged")]
+	[JsonInclude, JsonPropertyName("acknowledged")]
 	public bool Acknowledged { get; init; }
 }

src/Elastic.Clients.Elasticsearch/_Generated/Api/AsyncSearch/GetAsyncSearchResponse.g.cs

@@ -26,35 +26,27 @@
 namespace Elastic.Clients.Elasticsearch.AsyncSearch;
 public sealed partial class GetAsyncSearchResponse<TDocument> : ElasticsearchResponse
 {
-	[JsonInclude]
-	[JsonPropertyName("expiration_time")]
+	[JsonInclude, JsonPropertyName("expiration_time")]
 	public DateTimeOffset? ExpirationTime { get; init; }
 
-	[JsonInclude]
-	[JsonPropertyName("expiration_time_in_millis")]
+	[JsonInclude, JsonPropertyName("expiration_time_in_millis")]
 	public long ExpirationTimeInMillis { get; init; }
 
-	[JsonInclude]
-	[JsonPropertyName("id")]
+	[JsonInclude, JsonPropertyName("id")]
 	public string? Id { get; init; }
 
-	[JsonInclude]
-	[JsonPropertyName("is_partial")]
+	[JsonInclude, JsonPropertyName("is_partial")]
 	public bool IsPartial { get; init; }
 
-	[JsonInclude]
-	[JsonPropertyName("is_running")]
+	[JsonInclude, JsonPropertyName("is_running")]
 	public bool IsRunning { get; init; }
 
-	[JsonInclude]
-	[JsonPropertyName("response")]
+	[JsonInclude, JsonPropertyName("response")]
 	public Elastic.Clients.Elasticsearch.AsyncSearch.AsyncSearch<TDocument> Response { get; init; }
 
-	[JsonInclude]
-	[JsonPropertyName("start_time")]
+	[JsonInclude, JsonPropertyName("start_time")]
 	public DateTimeOffset? StartTime { get; init; }
 
-	[JsonInclude]
-	[JsonPropertyName("start_time_in_millis")]
+	[JsonInclude, JsonPropertyName("start_time_in_millis")]
 	public long StartTimeInMillis { get; init; }
 }