Support multiple expand_wildcards (#5317)

Since 7.10.1 the watcher expand_wildcards property has accepted and
returns an array for expanded_wildcards. This broke in our existing
representation of IndicesOptions during deserialisation. This change is
breaking but now supports either a single string value or an array in
the JSON response.

Author: stevejgordon

src/Nest/XPack/Watcher/Input/ExpandWildcardsFormatter.cs

@@ -0,0 +1,45 @@
+// 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.Linq;
+using Elasticsearch.Net;
+using Elasticsearch.Net.Utf8Json;
+
+namespace Nest
+{
+	internal class ExpandWildcardsFormatter : IJsonFormatter<IEnumerable<ExpandWildcards>>
+	{
+		public IEnumerable<ExpandWildcards> Deserialize(ref JsonReader reader, IJsonFormatterResolver formatterResolver)
+		{
+			var token = reader.GetCurrentJsonToken();
+			return token == JsonToken.BeginArray
+				? formatterResolver.GetFormatter<IEnumerable<ExpandWildcards>>().Deserialize(ref reader, formatterResolver)
+				: new[] { formatterResolver.GetFormatter<ExpandWildcards>().Deserialize(ref reader, formatterResolver) };
+		}
+
+		public void Serialize(ref JsonWriter writer, IEnumerable<ExpandWildcards> value, IJsonFormatterResolver formatterResolver)
+		{
+			if (value == null)
+			{
+				writer.WriteNull();
+				return;
+			}
+
+			var wildcards = value.ToArray();
+
+			switch (wildcards.Length)
+			{
+				case 1:
+					var singleFormatter = formatterResolver.GetFormatter<ExpandWildcards>();
+					singleFormatter.Serialize(ref writer, wildcards.First(), formatterResolver);
+					break;
+				case > 1:
+					var formatter = formatterResolver.GetFormatter<IEnumerable<ExpandWildcards>>();
+					formatter.Serialize(ref writer, wildcards, formatterResolver);
+					break;
+			}
+		}
+	}
+}

src/Nest/XPack/Watcher/Input/IndicesOptions.cs

@@ -2,6 +2,7 @@
 // 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.Runtime.Serialization;
 using Elasticsearch.Net;
 using Nest.Utf8Json;
@@ -15,28 +16,40 @@ public interface IIndicesOptions
 		[DataMember(Name = "allow_no_indices")]
 		bool? AllowNoIndices { get; set; }
 
+		/// <summary>
+		/// Determines how to expand indices wildcards.
+		/// <para>NOTE: Elasticsearch 7.10.0 and prior supports only a single value. Elasticsearch 7.10.1 and later support multiple values.</para>
+		/// </summary>
 		[DataMember(Name = "expand_wildcards")]
-		ExpandWildcards? ExpandWildcards { get; set; }
+		[JsonFormatter(typeof(ExpandWildcardsFormatter))]
+		IEnumerable<ExpandWildcards> ExpandWildcards { get; set; }
 
 		[DataMember(Name = "ignore_unavailable")]
 		bool? IgnoreUnavailable { get; set; }
 	}
 
 	[DataContract]
+	
 	public class IndicesOptions : IIndicesOptions
 	{
 		public bool? AllowNoIndices { get; set; }
-		public ExpandWildcards? ExpandWildcards { get; set; }
+		/// <inheritdoc />
+		public IEnumerable<ExpandWildcards> ExpandWildcards { get; set; }
 		public bool? IgnoreUnavailable { get; set; }
 	}
 
 	public class IndicesOptionsDescriptor : DescriptorBase<IndicesOptionsDescriptor, IIndicesOptions>, IIndicesOptions
 	{
 		bool? IIndicesOptions.AllowNoIndices { get; set; }
-		ExpandWildcards? IIndicesOptions.ExpandWildcards { get; set; }
+		IEnumerable<ExpandWildcards> IIndicesOptions.ExpandWildcards { get; set; }
 		bool? IIndicesOptions.IgnoreUnavailable { get; set; }
 
-		public IndicesOptionsDescriptor ExpandWildcards(ExpandWildcards? expandWildcards) =>
+		/// <inheritdoc cref="IIndicesOptions.ExpandWildcards"/>
+		public IndicesOptionsDescriptor ExpandWildcards(IEnumerable<ExpandWildcards> expandWildcards) =>
+			Assign(expandWildcards, (a, v) => a.ExpandWildcards = v);
+
+		/// <inheritdoc cref="IIndicesOptions.ExpandWildcards"/>
+		public IndicesOptionsDescriptor ExpandWildcards(params ExpandWildcards[] expandWildcards) =>
 			Assign(expandWildcards, (a, v) => a.ExpandWildcards = v);
 
 		public IndicesOptionsDescriptor IgnoreUnavailable(bool? ignoreUnavailable = true) =>

tests/Tests/XPack/Watcher/GetWatch/GetWatchApiTests.cs

@@ -118,6 +118,7 @@ public static void PutWatch(IElasticClient client, CallUniqueValues values)
 										.Indices(typeof(Project))
 										.SearchType(SearchType.DfsQueryThenFetch)
 										.IndicesOptions(io => io
+											.AllowNoIndices()
 											.ExpandWildcards(ExpandWildcards.Open)
 											.IgnoreUnavailable()
 										)