support predicate_token_filter elastic/elasticsearch#33431

src/Nest/Analysis/TokenFilters/PredicateTokenFilter .cs

@@ -0,0 +1,43 @@
+using System;
+using Newtonsoft.Json;
+
+namespace Nest
+{
+	/// <summary>
+	/// The predicate_token_filter token filter takes a predicate script, and removes tokens that do
+	/// not match the predicate.
+	/// </summary>
+	public interface IPredicateTokenFilter : ITokenFilter
+	{
+		/// <summary>
+		/// a predicate script that determines whether or not the current token will
+		/// be emitted.  Note that only inline scripts are supported.
+		/// </summary>
+		[JsonProperty("script")]
+		IScript Script { get; set; }
+	}
+
+	public class PredicateTokenFilter : TokenFilterBase, IPredicateTokenFilter
+	{
+		public PredicateTokenFilter() : base("predicate_token_filter") { }
+
+		public IScript Script { get; set; }
+	}
+
+	/// <inheritdoc cref="IPredicateTokenFilter" />
+	public class PredicateTokenFilterDescriptor
+		: TokenFilterDescriptorBase<PredicateTokenFilterDescriptor, IPredicateTokenFilter>, IPredicateTokenFilter
+	{
+		protected override string Type => "predicate_token_filter";
+
+		IScript IPredicateTokenFilter.Script { get; set; }
+
+		/// <inheritdoc cref="IPredicateTokenFilter.Script" />
+		public PredicateTokenFilterDescriptor Script(Func<ScriptDescriptor, IScript> scriptSelector) =>
+			Assign(a => a.Script = scriptSelector?.Invoke(new ScriptDescriptor()));
+
+		/// <inheritdoc cref="IPredicateTokenFilter.Script" />
+		public PredicateTokenFilterDescriptor Script(string predicate) =>
+			Assign(a => a.Script = new InlineScript(predicate));
+	}
+}

src/Nest/Analysis/TokenFilters/TokenFilters.cs

@@ -225,6 +225,10 @@ public TokenFiltersDescriptor Standard(string name, Func<StandardTokenFilterDesc
 		public TokenFiltersDescriptor Stemmer(string name, Func<StemmerTokenFilterDescriptor, IStemmerTokenFilter> selector) =>
 			Assign(name, selector?.Invoke(new StemmerTokenFilterDescriptor()));
 
+		/// <inheritdoc cref="IPredicateTokenFilter" />
+		public TokenFiltersDescriptor Predicate(string name, Func<PredicateTokenFilterDescriptor, IPredicateTokenFilter> selector) =>
+			Assign(name, selector?.Invoke(new PredicateTokenFilterDescriptor()));
+
 		/// <inheritdoc cref="IConditionTokenFilter" />
 		public TokenFiltersDescriptor Condition(string name, Func<ConditionTokenFilterDescriptor, IConditionTokenFilter> selector) =>
 			Assign(name, selector?.Invoke(new ConditionTokenFilterDescriptor()));

src/Nest/Indices/Analyze/AnalyzeTokenFilters.cs

@@ -251,6 +251,10 @@ public AnalyzeTokenFiltersDescriptor Condition(Func<ConditionTokenFilterDescript
 		public AnalyzeTokenFiltersDescriptor Stemmer(Func<StemmerTokenFilterDescriptor, IStemmerTokenFilter> selector) =>
 			AssignIfNotNull(selector?.Invoke(new StemmerTokenFilterDescriptor()));
 
+		/// <inheritdoc cref="IPredicateTokenFilter" />
+		public AnalyzeTokenFiltersDescriptor Predicate(Func<PredicateTokenFilterDescriptor, IPredicateTokenFilter> selector) =>
+			AssignIfNotNull(selector?.Invoke(new PredicateTokenFilterDescriptor()));
+
 		/// <summary>
 		/// Overrides stemming algorithms, by applying a custom mapping, then protecting these terms from being modified by stemmers. Must be placed
 		/// before any stemming filters.

src/Tests/Tests/Analysis/TokenFilters/TokenFilterTests.cs

@@ -584,6 +584,28 @@ public class StemmerTests : TokenFilterAssertionBase<StemmerTests>
 			public override string Name => "stem";
 		}
 
+		[SkipVersion("<6.5.0", "predicate token filter not available in earlier versions")]
+		public class PredicateTests : TokenFilterAssertionBase<PredicateTests>
+		{
+			private readonly string _predicate = "token.getTerm().length() > 5";
+
+			public override FuncTokenFilters Fluent => (n, tf) => tf.Predicate(n, t => t.Script(_predicate));
+
+			public override ITokenFilter Initializer => new PredicateTokenFilter { Script = new InlineScript(_predicate) };
+
+			public override object Json => new
+			{
+				type = "predicate_token_filter",
+				script = new
+				{
+					source = _predicate
+				}
+			};
+
+			public override string Name => "predicate";
+		}
+
+
 		public class StemmerOverrideTests : TokenFilterAssertionBase<StemmerOverrideTests>
 		{
 			public override FuncTokenFilters Fluent => (n, tf) => tf.StemmerOverride(n, t => t.RulesPath("analysis/custom_stems.txt"));