Add lenient to synonym and synonym_graph token filters (#3428)

(cherry picked from commit 1adc417)

Author: Mpdreamz

src/Nest/Analysis/TokenFilters/Synonym/SynonymGraphTokenFilter.cs

@@ -31,6 +31,10 @@ public interface ISynonymGraphTokenFilter : ITokenFilter
 
 		[JsonProperty("tokenizer")]
 		string Tokenizer { get; set; }
+
+		/// <inheritdoc cref="ISynonymTokenFilter.Lenient"/>
+		[JsonProperty("lenient")]
+		bool? Lenient { get; set; }
 	}
 
 	/// <inheritdoc/>
@@ -54,6 +58,9 @@ public SynonymGraphTokenFilter() : base("synonym_graph") { }
 		/// <inheritdoc/>
 		public bool? Expand { get; set; }
 
+		/// <inheritdoc cref="ISynonymTokenFilter.Lenient"/>
+		public bool? Lenient { get; set; }
+
 		/// <inheritdoc/>
 		public string Tokenizer { get; set; }
 	}
@@ -65,6 +72,7 @@ public class SynonymGraphTokenFilterDescriptor
 
 		bool? ISynonymGraphTokenFilter.IgnoreCase { get; set; }
 		bool? ISynonymGraphTokenFilter.Expand { get; set; }
+		bool? ISynonymGraphTokenFilter.Lenient { get; set; }
 		string ISynonymGraphTokenFilter.Tokenizer { get; set; }
 		string ISynonymGraphTokenFilter.SynonymsPath { get; set; }
 		SynonymFormat? ISynonymGraphTokenFilter.Format{ get; set; }
@@ -78,6 +86,10 @@ public class SynonymGraphTokenFilterDescriptor
 		///<inheritdoc/>
 		public SynonymGraphTokenFilterDescriptor Expand(bool? expand = true) => Assign(a => a.Expand = expand);
 
+		/// <inheritdoc cref="ISynonymTokenFilter.Lenient"/>
+		public SynonymGraphTokenFilterDescriptor Lenient(bool? lenient = true) => Assign(a => a.Lenient = lenient);
+
+
 		///<inheritdoc/>
 		public SynonymGraphTokenFilterDescriptor Tokenizer(string tokenizer) => Assign(a => a.Tokenizer = tokenizer);
 

src/Nest/Analysis/TokenFilters/Synonym/SynonymTokenFilter.cs

@@ -30,6 +30,13 @@ public interface ISynonymTokenFilter : ITokenFilter
 
 		[JsonProperty("tokenizer")]
 		string Tokenizer { get; set; }
+
+		/// <summary>
+		/// If `true` ignores exceptions while parsing the synonym configuration. It is important
+		// to note that only those synonym rules which cannot get parsed are ignored.
+		/// </summary>
+		[JsonProperty("lenient")]
+		bool? Lenient { get; set; }
 	}
 
 	/// <inheritdoc/>
@@ -53,6 +60,9 @@ public SynonymTokenFilter() : base("synonym") { }
 		/// <inheritdoc/>
 		public bool? Expand { get; set; }
 
+		/// <inheritdoc cref="ISynonymTokenFilter.Lenient"/>
+		public bool? Lenient { get; set; }
+
 		/// <inheritdoc/>
 		public string Tokenizer { get; set; }
 	}
@@ -64,6 +74,7 @@ public class SynonymTokenFilterDescriptor
 
 		bool? ISynonymTokenFilter.IgnoreCase { get; set; }
 		bool? ISynonymTokenFilter.Expand { get; set; }
+		bool? ISynonymTokenFilter.Lenient { get; set; }
 		string ISynonymTokenFilter.Tokenizer { get; set; }
 		string ISynonymTokenFilter.SynonymsPath { get; set; }
 		SynonymFormat? ISynonymTokenFilter.Format { get; set; }
@@ -76,6 +87,9 @@ public class SynonymTokenFilterDescriptor
 		///<inheritdoc/>
 		public SynonymTokenFilterDescriptor Expand(bool? expand = true) => Assign(a => a.Expand = expand);
 
+		/// <inheritdoc cref="ISynonymTokenFilter.Lenient"/>
+		public SynonymTokenFilterDescriptor Lenient(bool? lenient = true) => Assign(a => a.Lenient = lenient);
+
 		///<inheritdoc/>
 		public SynonymTokenFilterDescriptor Tokenizer(string tokenizer) => Assign(a => a.Tokenizer = tokenizer);
 

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

@@ -674,7 +674,33 @@ public class SynonymTests : TokenFilterAssertionBase<SynonymTests>
 				expand = true,
 				tokenizer = "whitespace"
 			};
+		}
+
+		[SkipVersion("<6.4.0", "Lenient is an option introduced in 6.4.0")]
+		public class SynonymLenientTests : TokenFilterAssertionBase<SynonymTests>
+		{
+			public override string Name => "syn";
+			private readonly string[] _synonyms = {"foo", "bar => baz"};
+
+			public override ITokenFilter Initializer =>
+				new SynonymTokenFilter
+				{
+					Lenient = true,
+					Synonyms = _synonyms
+				};
 
+			public override FuncTokenFilters Fluent => (n, tf) => tf
+				.Synonym(n, t => t
+					.Lenient()
+					.Synonyms(_synonyms)
+				);
+
+			public override object Json => new
+			{
+				type = "synonym",
+				synonyms = _synonyms,
+				lenient = true,
+			};
 		}
 
 		public class SynonymGraphTests : TokenFilterAssertionBase<SynonymGraphTests>