Fix #3320 Add Painless script execute API (#3370)

* Generate ExcecutePainlessScript methods/descriptors etc

* Implement ExecutePainlessScript API with tests

Omitting `context` for now since that only takes a single option now
which is also the default. Waiting for the API to crystalize here.

* make Result generic in preparation for 6.4

Author: Mpdreamz

src/CodeGeneration/ApiGenerator/ApiGenerator.cs

@@ -84,8 +84,6 @@ public static void Generate(string downloadBranch, params string[] folders)
 			"xpack.sql.query.json",
 			"xpack.sql.translate.json",
 			"xpack.ssl.certificates.json",
-
-			"scripts_painless_execute.json",
 		};
 
 		private static RestApiSpec CreateRestApiSpecModel(string downloadBranch, string[] folders)

src/Elasticsearch.Net/Domain/RequestParameters/RequestParameters.Generated.cs

@@ -1753,6 +1753,11 @@ public partial class RenderSearchTemplateRequestParameters : RequestParameters<R
 	{
 		public override HttpMethod DefaultHttpMethod => HttpMethod.POST;
 	}
+	///<summary>Request options for ScriptsPainlessExecute<pre>https://www.elastic.co/guide/en/elasticsearch/painless/master/painless-execute-api.html</pre></summary>
+	public partial class ExecutePainlessScriptRequestParameters : RequestParameters<ExecutePainlessScriptRequestParameters> 
+	{
+		public override HttpMethod DefaultHttpMethod => HttpMethod.POST;
+	}
 	///<summary>Request options for Scroll<pre>http://www.elastic.co/guide/en/elasticsearch/reference/master/search-request-scroll.html</pre></summary>
 	public partial class ScrollRequestParameters : RequestParameters<ScrollRequestParameters> 
 	{

src/Elasticsearch.Net/ElasticLowLevelClient.Generated.cs

@@ -2416,6 +2416,24 @@ public TResponse RenderSearchTemplate<TResponse>(string id, PostData body, Rende
 		///<param name="requestParameters">A func that allows you to describe the querystring parameters &amp; request specific connection settings.</param>
 		public Task<TResponse> RenderSearchTemplateAsync<TResponse>(string id, PostData body, RenderSearchTemplateRequestParameters requestParameters = null, CancellationToken ctx = default(CancellationToken))
 			where TResponse : class, IElasticsearchResponse, new() => this.DoRequestAsync<TResponse>(POST, Url($"_render/template/{id.NotNull("id")}"), ctx, body, _params(requestParameters));
+		///<summary>GET on /_scripts/painless/_execute <para>https://www.elastic.co/guide/en/elasticsearch/painless/master/painless-execute-api.html</para></summary>
+		///<param name="requestParameters">A func that allows you to describe the querystring parameters &amp; request specific connection settings.</param>
+		public TResponse ScriptsPainlessExecuteGet<TResponse>(ExecutePainlessScriptRequestParameters requestParameters = null)
+			where TResponse : class, IElasticsearchResponse, new() => this.DoRequest<TResponse>(GET, Url($"_scripts/painless/_execute"), null, _params(requestParameters));
+		///<summary>GET on /_scripts/painless/_execute <para>https://www.elastic.co/guide/en/elasticsearch/painless/master/painless-execute-api.html</para></summary>
+		///<param name="requestParameters">A func that allows you to describe the querystring parameters &amp; request specific connection settings.</param>
+		public Task<TResponse> ScriptsPainlessExecuteGetAsync<TResponse>(ExecutePainlessScriptRequestParameters requestParameters = null, CancellationToken ctx = default(CancellationToken))
+			where TResponse : class, IElasticsearchResponse, new() => this.DoRequestAsync<TResponse>(GET, Url($"_scripts/painless/_execute"), ctx, null, _params(requestParameters));
+		///<summary>POST on /_scripts/painless/_execute <para>https://www.elastic.co/guide/en/elasticsearch/painless/master/painless-execute-api.html</para></summary>
+		///<param name="body">The script to execute</param>
+		///<param name="requestParameters">A func that allows you to describe the querystring parameters &amp; request specific connection settings.</param>
+		public TResponse ScriptsPainlessExecute<TResponse>(PostData body, ExecutePainlessScriptRequestParameters requestParameters = null)
+			where TResponse : class, IElasticsearchResponse, new() => this.DoRequest<TResponse>(POST, Url($"_scripts/painless/_execute"), body, _params(requestParameters));
+		///<summary>POST on /_scripts/painless/_execute <para>https://www.elastic.co/guide/en/elasticsearch/painless/master/painless-execute-api.html</para></summary>
+		///<param name="body">The script to execute</param>
+		///<param name="requestParameters">A func that allows you to describe the querystring parameters &amp; request specific connection settings.</param>
+		public Task<TResponse> ScriptsPainlessExecuteAsync<TResponse>(PostData body, ExecutePainlessScriptRequestParameters requestParameters = null, CancellationToken ctx = default(CancellationToken))
+			where TResponse : class, IElasticsearchResponse, new() => this.DoRequestAsync<TResponse>(POST, Url($"_scripts/painless/_execute"), ctx, body, _params(requestParameters));
 		///<summary>GET on /_search/scroll <para>http://www.elastic.co/guide/en/elasticsearch/reference/master/search-request-scroll.html</para></summary>
 		///<param name="requestParameters">A func that allows you to describe the querystring parameters &amp; request specific connection settings.</param>
 		public TResponse ScrollGet<TResponse>(ScrollRequestParameters requestParameters = null)

src/Elasticsearch.Net/IElasticLowLevelClient.Generated.cs

@@ -1956,6 +1956,20 @@ public partial interface IElasticLowLevelClient
 		///<param name="body">The search definition template and its params</param>
 		///<param name="requestParameters">A func that allows you to describe the querystring parameters &amp; request specific connection settings.</param>
 		Task<TResponse> RenderSearchTemplateAsync<TResponse>(string id, PostData body, RenderSearchTemplateRequestParameters requestParameters = null, CancellationToken ctx = default(CancellationToken)) where TResponse : class, IElasticsearchResponse, new();
+		///<summary>GET on /_scripts/painless/_execute <para>https://www.elastic.co/guide/en/elasticsearch/painless/master/painless-execute-api.html</para></summary>
+		///<param name="requestParameters">A func that allows you to describe the querystring parameters &amp; request specific connection settings.</param>
+		TResponse ScriptsPainlessExecuteGet<TResponse>(ExecutePainlessScriptRequestParameters requestParameters = null) where TResponse : class, IElasticsearchResponse, new();
+		///<summary>GET on /_scripts/painless/_execute <para>https://www.elastic.co/guide/en/elasticsearch/painless/master/painless-execute-api.html</para></summary>
+		///<param name="requestParameters">A func that allows you to describe the querystring parameters &amp; request specific connection settings.</param>
+		Task<TResponse> ScriptsPainlessExecuteGetAsync<TResponse>(ExecutePainlessScriptRequestParameters requestParameters = null, CancellationToken ctx = default(CancellationToken)) where TResponse : class, IElasticsearchResponse, new();
+		///<summary>POST on /_scripts/painless/_execute <para>https://www.elastic.co/guide/en/elasticsearch/painless/master/painless-execute-api.html</para></summary>
+		///<param name="body">The script to execute</param>
+		///<param name="requestParameters">A func that allows you to describe the querystring parameters &amp; request specific connection settings.</param>
+		TResponse ScriptsPainlessExecute<TResponse>(PostData body, ExecutePainlessScriptRequestParameters requestParameters = null) where TResponse : class, IElasticsearchResponse, new();
+		///<summary>POST on /_scripts/painless/_execute <para>https://www.elastic.co/guide/en/elasticsearch/painless/master/painless-execute-api.html</para></summary>
+		///<param name="body">The script to execute</param>
+		///<param name="requestParameters">A func that allows you to describe the querystring parameters &amp; request specific connection settings.</param>
+		Task<TResponse> ScriptsPainlessExecuteAsync<TResponse>(PostData body, ExecutePainlessScriptRequestParameters requestParameters = null, CancellationToken ctx = default(CancellationToken)) where TResponse : class, IElasticsearchResponse, new();
 		///<summary>GET on /_search/scroll <para>http://www.elastic.co/guide/en/elasticsearch/reference/master/search-request-scroll.html</para></summary>
 		///<param name="requestParameters">A func that allows you to describe the querystring parameters &amp; request specific connection settings.</param>
 		TResponse ScrollGet<TResponse>(ScrollRequestParameters requestParameters = null) where TResponse : class, IElasticsearchResponse, new();

src/Nest/Modules/Scripting/ExecutePainlessScript/ElasticClient-ExecutePainlessScript.cs

@@ -0,0 +1,54 @@
+using System;
+using System.Threading.Tasks;
+using Elasticsearch.Net;
+using System.Threading;
+
+namespace Nest
+{
+	public partial interface IElasticClient
+	{
+		/// <summary>
+		/// Executes an arbitrary Painless script and returns a result.
+		/// Useful for testing the syntactical correctness of Painless scripts
+		/// </summary>
+		IExecutePainlessScriptResponse<TResult> ExecutePainlessScript<TResult>(Func<ExecutePainlessScriptDescriptor, IExecutePainlessScriptRequest> selector);
+
+		/// <inheritdoc cref="ExecutePainlessScript{TResult}(System.Func{Nest.ExecutePainlessScriptDescriptor,Nest.IExecutePainlessScriptRequest})"/>
+		IExecutePainlessScriptResponse<TResult> ExecutePainlessScript<TResult>(IExecutePainlessScriptRequest request);
+
+		/// <inheritdoc cref="ExecutePainlessScript{TResult}(System.Func{Nest.ExecutePainlessScriptDescriptor,Nest.IExecutePainlessScriptRequest})"/>
+		Task<IExecutePainlessScriptResponse<TResult>> ExecutePainlessScriptAsync<TResult>(Func<ExecutePainlessScriptDescriptor, IExecutePainlessScriptRequest> selector,
+			CancellationToken cancellationToken = default(CancellationToken));
+
+		/// <inheritdoc cref="ExecutePainlessScript{TResult}(System.Func{Nest.ExecutePainlessScriptDescriptor,Nest.IExecutePainlessScriptRequest})"/>
+		Task<IExecutePainlessScriptResponse<TResult>> ExecutePainlessScriptAsync<TResult>(IExecutePainlessScriptRequest request, CancellationToken cancellationToken = default(CancellationToken));
+
+	}
+
+	public partial class ElasticClient
+	{
+		/// <inheritdoc />
+		public IExecutePainlessScriptResponse<TResult> ExecutePainlessScript<TResult>(Func<ExecutePainlessScriptDescriptor, IExecutePainlessScriptRequest> selector) =>
+			this.ExecutePainlessScript<TResult>(selector?.Invoke(new ExecutePainlessScriptDescriptor()));
+
+		/// <inheritdoc />
+		public IExecutePainlessScriptResponse<TResult> ExecutePainlessScript<TResult>(IExecutePainlessScriptRequest request) =>
+			this.Dispatcher.Dispatch<IExecutePainlessScriptRequest, ExecutePainlessScriptRequestParameters, ExecutePainlessScriptResponse<TResult>>(
+				request,
+				this.LowLevelDispatch.ScriptsPainlessExecuteDispatch<ExecutePainlessScriptResponse<TResult>>
+			);
+
+		/// <inheritdoc />
+		public Task<IExecutePainlessScriptResponse<TResult>> ExecutePainlessScriptAsync<TResult>(Func<ExecutePainlessScriptDescriptor, IExecutePainlessScriptRequest> selector,
+			CancellationToken cancellationToken = default(CancellationToken)) =>
+			this.ExecutePainlessScriptAsync<TResult>(selector?.Invoke(new ExecutePainlessScriptDescriptor()), cancellationToken);
+
+		/// <inheritdoc />
+		public Task<IExecutePainlessScriptResponse<TResult>> ExecutePainlessScriptAsync<TResult>(IExecutePainlessScriptRequest request, CancellationToken cancellationToken = default(CancellationToken)) =>
+			this.Dispatcher.DispatchAsync<IExecutePainlessScriptRequest, ExecutePainlessScriptRequestParameters, ExecutePainlessScriptResponse<TResult>, IExecutePainlessScriptResponse<TResult>>(
+				request,
+				cancellationToken,
+				this.LowLevelDispatch.ScriptsPainlessExecuteDispatchAsync<ExecutePainlessScriptResponse<TResult>>
+			);
+	}
+}

src/Nest/Modules/Scripting/ExecutePainlessScript/ExecutePainlessScriptRequest.cs

@@ -0,0 +1,25 @@
+using System;
+using Newtonsoft.Json;
+
+namespace Nest
+{
+	public partial interface IExecutePainlessScriptRequest
+	{
+		[JsonProperty("script")]
+		IInlineScript Script { get; set; }
+	}
+
+	public partial class ExecutePainlessScriptRequest
+	{
+		public IInlineScript Script { get; set; }
+	}
+
+	[DescriptorFor("ScriptsPainlessExecute")]
+	public partial class ExecutePainlessScriptDescriptor
+	{
+		IInlineScript IExecutePainlessScriptRequest.Script { get; set; }
+
+		public ExecutePainlessScriptDescriptor Script(Func<InlineScriptDescriptor, IInlineScript> selector) =>
+			Assign(a => a.Script = selector?.Invoke(new InlineScriptDescriptor()));
+	}
+}

src/Nest/Modules/Scripting/ExecutePainlessScript/ExecutePainlessScriptResponse.cs

@@ -0,0 +1,15 @@
+using Newtonsoft.Json;
+
+namespace Nest
+{
+	public interface IExecutePainlessScriptResponse<TResult> : IResponse
+	{
+		[JsonProperty("result")]
+		TResult Result { get; }
+	}
+
+	public class ExecutePainlessScriptResponse<TResult> : ResponseBase, IExecutePainlessScriptResponse<TResult>
+	{
+		public TResult Result { get; set; }
+	}
+}

src/Nest/_Generated/_Descriptors.generated.cs

@@ -3126,6 +3126,14 @@ public RenderSearchTemplateDescriptor() : base(){}
 
 		// Request parameters
 
+	}
+	///<summary>descriptor for ScriptsPainlessExecute <pre>https://www.elastic.co/guide/en/elasticsearch/painless/master/painless-execute-api.html</pre></summary>
+	public partial class ExecutePainlessScriptDescriptor  : RequestDescriptorBase<ExecutePainlessScriptDescriptor,ExecutePainlessScriptRequestParameters, IExecutePainlessScriptRequest>, IExecutePainlessScriptRequest
+	{ 
+		// values part of the url path
+
+		// Request parameters
+
 	}
 	///<summary>descriptor for Scroll <pre>http://www.elastic.co/guide/en/elasticsearch/reference/master/search-request-scroll.html</pre></summary>
 	public partial class ScrollDescriptor<T>  : RequestDescriptorBase<ScrollDescriptor<T>,ScrollRequestParameters, IScrollRequest>, IScrollRequest

src/Nest/_Generated/_LowLevelDispatch.generated.cs

@@ -2408,6 +2408,30 @@ internal partial class LowLevelDispatch
 			throw InvalidDispatch("RenderSearchTemplate", p, new [] { GET, POST }, "/_render/template", "/_render/template/{id}");
 		}
 
+		internal TResponse ScriptsPainlessExecuteDispatch<TResponse>(IRequest<ExecutePainlessScriptRequestParameters> p,SerializableData<IExecutePainlessScriptRequest> body) where TResponse : class, IElasticsearchResponse, new()
+		{
+			switch(p.HttpMethod)
+			{
+				case GET:
+						return _lowLevel.ScriptsPainlessExecuteGet<TResponse>(p.RequestParameters);
+				case POST:
+						return _lowLevel.ScriptsPainlessExecute<TResponse>(body,p.RequestParameters);
+			}
+			throw InvalidDispatch("ScriptsPainlessExecute", p, new [] { GET, POST }, "/_scripts/painless/_execute");
+		}
+		
+		internal Task<TResponse> ScriptsPainlessExecuteDispatchAsync<TResponse>(IRequest<ExecutePainlessScriptRequestParameters> p,SerializableData<IExecutePainlessScriptRequest> body, CancellationToken ct) where TResponse : class, IElasticsearchResponse, new()
+		{
+			switch(p.HttpMethod)
+			{
+				case GET:
+						return _lowLevel.ScriptsPainlessExecuteGetAsync<TResponse>(p.RequestParameters,ct);
+				case POST:
+						return _lowLevel.ScriptsPainlessExecuteAsync<TResponse>(body,p.RequestParameters,ct);
+			}
+			throw InvalidDispatch("ScriptsPainlessExecute", p, new [] { GET, POST }, "/_scripts/painless/_execute");
+		}
+		
 		internal TResponse ScrollDispatch<TResponse>(IRequest<ScrollRequestParameters> p,SerializableData<IScrollRequest> body) where TResponse : class, IElasticsearchResponse, new()
 		{
 			switch(p.HttpMethod)

src/Nest/_Generated/_Requests.generated.cs

@@ -2247,6 +2247,18 @@ public EnableUserRequest(Name username) : base(r=>r.Optional("username", usernam
 		public Refresh? Refresh { get => Q<Refresh?>("refresh"); set => Q("refresh", value); }
 	}
 	[JsonObject(MemberSerialization = MemberSerialization.OptIn)]
+	public partial interface IExecutePainlessScriptRequest : IRequest<ExecutePainlessScriptRequestParameters>
+	{
+	}
+	///<summary>Request parameters for ScriptsPainlessExecute <pre>https://www.elastic.co/guide/en/elasticsearch/painless/master/painless-execute-api.html</pre></summary>
+	public partial class ExecutePainlessScriptRequest : PlainRequestBase<ExecutePainlessScriptRequestParameters>, IExecutePainlessScriptRequest
+	{
+		protected IExecutePainlessScriptRequest Self => this;
+		// values part of the url path
+
+		// Request parameters
+	}
+	[JsonObject(MemberSerialization = MemberSerialization.OptIn)]
 	public partial interface IExecuteWatchRequest : IRequest<ExecuteWatchRequestParameters>
 	{
 		Id Id { get; }

src/Tests/Tests/Modules/Scripting/ExecutePainlessScript/ExecutePainlessScriptApiTests.cs

@@ -0,0 +1,72 @@
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Elastic.Xunit.XunitPlumbing;
+using Elasticsearch.Net;
+using FluentAssertions;
+using Nest;
+using Tests.Core.Extensions;
+using Tests.Core.ManagedElasticsearch.Clusters;
+using Tests.Framework;
+using Tests.Framework.Integration;
+using Tests.Framework.ManagedElasticsearch.Clusters;
+using Xunit;
+
+namespace Tests.Modules.Scripting.ExecutePainlessScript
+{
+	[SkipVersion("<6.3.0", "this API was introduced in 6.3.0")]
+	public class ExecutePainlessScriptApiTests
+		: ApiIntegrationTestBase<ReadOnlyCluster, IExecutePainlessScriptResponse<string>, IExecutePainlessScriptRequest, ExecutePainlessScriptDescriptor, ExecutePainlessScriptRequest>
+	{
+		public ExecutePainlessScriptApiTests(ReadOnlyCluster cluster, EndpointUsage usage) : base(cluster, usage) { }
+
+		private static readonly string _painlessScript = "params.count / params.total";
+
+		protected override LazyResponses ClientUsage() => Calls(
+			fluent: (client, f) => client.ExecutePainlessScript<string>(f),
+			fluentAsync: (client, f) => client.ExecutePainlessScriptAsync<string>(f),
+			request: (client, r) => client.ExecutePainlessScript<string>(r),
+			requestAsync: (client, r) => client.ExecutePainlessScriptAsync<string>(r)
+		);
+
+		protected override HttpMethod HttpMethod => HttpMethod.POST;
+		protected override string UrlPath => "/_scripts/painless/_execute";
+		protected override int ExpectStatusCode => 200;
+		protected override bool ExpectIsValid => true;
+
+		protected override bool SupportsDeserialization => false;
+
+		protected override object ExpectJson => new
+		{
+			script = new
+			{
+				source = _painlessScript,
+				@params = new { count = 100.0, total = 1000.0 }
+			},
+		};
+
+		protected override Func<ExecutePainlessScriptDescriptor, IExecutePainlessScriptRequest> Fluent => d => d
+			.Script(s=>s
+				.Source(_painlessScript)
+				.Params(p => p.Add("count", 100.0).Add("total", 1000.0))
+			);
+
+		protected override ExecutePainlessScriptRequest Initializer => new ExecutePainlessScriptRequest
+		{
+			Script = new InlineScript(_painlessScript)
+			{
+				Params = new Dictionary<string, object>
+				{
+					{ "count", 100.0 },
+					{ "total", 1000.0 },
+				}
+			}
+		};
+
+		protected override void ExpectResponse(IExecutePainlessScriptResponse<string> response)
+		{
+			response.ShouldBeValid();
+			response.Result.Should().NotBeNullOrWhiteSpace();
+		}
+	}
+}

src/Tests/Tests/Modules/Scripting/ExecutePainlessScript/ExecutePainlessScriptUrlTests.cs

@@ -0,0 +1,27 @@
+using System.Threading.Tasks;
+using Elastic.Xunit.XunitPlumbing;
+using Nest;
+using Tests.Framework;
+using static Tests.Framework.UrlTester;
+
+namespace Tests.Modules.Scripting.ExecutePainlessScript
+{
+	public class ExecutePainlessScriptUrlTests
+	{
+		[U] public async Task Urls()
+		{
+			var painless = "1 + 1";
+			var request = new ExecutePainlessScriptRequest
+			{
+				Script = new InlineScript(painless)
+			};
+
+			await POST("/_scripts/painless/_execute")
+				.Fluent(c => c.ExecutePainlessScript<string>(f => f.Script(s => s.Source(painless))))
+				.Request(c => c.ExecutePainlessScript<string>(request))
+				.FluentAsync(c => c.ExecutePainlessScriptAsync<string>(f => f.Script(s => s.Source(painless))))
+				.RequestAsync(c => c.ExecutePainlessScriptAsync<string>(request))
+				;
+		}
+	}
+}