Add description to ingest processors (#4871) (#4882)

This commit adds description to ingest processors to allow
users to explain the purpose of a specific processor instance.

Co-authored-by: Russ Cam <russ.cam@elastic.co>

Author: github-actions[bot]

src/Nest/Ingest/Processor.cs

@@ -2,7 +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;
+using System;
 using System.Collections.Generic;
 using System.Runtime.Serialization;
 using Elasticsearch.Net.Utf8Json;
@@ -18,6 +18,14 @@ public interface IProcessor
 		[IgnoreDataMember]
 		string Name { get; }
 
+		/// <summary>
+		/// A description to explain the purpose of the specific processor instance.
+		/// <para />
+		/// Valid in Elasticsearch 7.9.0+
+		/// </summary>
+		[DataMember(Name = "description")]
+		string Description { get; set; }
+
 		/// <summary>
 		/// If a processor fails, call these processors instead. Read more about handling failures here:
 		/// https://www.elastic.co/guide/en/elasticsearch/reference/current/handling-failure-in-pipelines.html
@@ -54,6 +62,9 @@ public abstract class ProcessorBase : IProcessor
 		/// <inheritdoc cref="IProcessor.OnFailure"/>
 		public IEnumerable<IProcessor> OnFailure { get; set; }
 		protected abstract string Name { get; }
+		/// <inheritdoc cref="IProcessor.Description"/>
+		public string Description { get; set; }
+
 		string IProcessor.Name => Name;
 	}
 
@@ -65,11 +76,15 @@ public abstract class ProcessorDescriptorBase<TProcessorDescriptor, TProcessorIn
 	{
 		protected abstract string Name { get; }
 		string IProcessor.Name => Name;
+		string IProcessor.Description { get; set; }
 		IEnumerable<IProcessor> IProcessor.OnFailure { get; set; }
 		string IProcessor.If { get; set; }
 		string IProcessor.Tag { get; set; }
 		bool? IProcessor.IgnoreFailure { get; set; }
 
+		/// <inheritdoc cref="IProcessor.Description"/>
+		public TProcessorDescriptor Description(string description) => Assign(description, (a, v) => a.Description = v);
+
 		/// <inheritdoc cref="IProcessor.OnFailure"/>
 		public TProcessorDescriptor OnFailure(IEnumerable<IProcessor> processors) => Assign(processors.ToListOrNullIfEmpty(), (a, v) => a.OnFailure = v);
 

tests/Tests/Ingest/ProcessorAssertions.cs

@@ -75,7 +75,7 @@ public class Append : ProcessorAssertion
 			public override string Key => "append";
 		}
 
-		[SkipVersion("<7.8.0", "Empty Value bug in versions less than Elasticsearch 7.8.0")]
+		[SkipVersion("<7.9.0", "Description added in 7.9.0")]
 		public class Csv : ProcessorAssertion
 		{
 			public override Func<ProcessorsDescriptor, IPromise<IList<IProcessor>>> Fluent => d => d
@@ -84,22 +84,25 @@ public class Csv : ProcessorAssertion
 					.TargetFields(new[] { "targetField1", "targetField2" })
 					.EmptyValue("empty")
 					.Trim()
+					.Description("parses CSV")
 				);
 
 			public override IProcessor Initializer => new CsvProcessor
 			{
 				Field = "name",
 				TargetFields = new[] { "targetField1", "targetField2" },
 				EmptyValue = "empty",
-				Trim = true
+				Trim = true,
+				Description = "parses CSV"
 			};
 
 			public override object Json => new
 			{
 				field = "name",
 				target_fields = new[] { "targetField1", "targetField2" },
 				empty_value = "empty",
-				trim = true
+				trim = true,
+				description = "parses CSV"
 			};
 
 			public override string Key => "csv";