Add PreserveOriginal to EdgeNgramTokenFilter

Relates: #4718

src/Nest/Analysis/TokenFilters/EdgeNGram/EdgeNGramTokenFilter.cs

@@ -31,6 +31,13 @@ public interface IEdgeNGramTokenFilter : ITokenFilter
 		/// </summary>
 		[DataMember(Name ="side")]
 		EdgeNGramSide? Side { get; set; }
+
+		/// <summary>
+		/// Emits original token when set to <c>true</c>. Defaults to <c>false</c>.
+		/// </summary>
+		[DataMember(Name = "preserve_original")]
+		[JsonFormatter(typeof(NullableStringBooleanFormatter))]
+		bool? PreserveOriginal { get; set; }
 	}
 
 	/// <inheritdoc />
@@ -46,6 +53,9 @@ public EdgeNGramTokenFilter() : base("edge_ngram") { }
 
 		/// <inheritdoc />
 		public EdgeNGramSide? Side { get; set; }
+
+		/// <inheritdoc />
+		public bool? PreserveOriginal { get; set; }
 	}
 
 	/// <inheritdoc />
@@ -54,17 +64,21 @@ public class EdgeNGramTokenFilterDescriptor
 	{
 		protected override string Type => "edge_ngram";
 		int? IEdgeNGramTokenFilter.MaxGram { get; set; }
-
 		int? IEdgeNGramTokenFilter.MinGram { get; set; }
 		EdgeNGramSide? IEdgeNGramTokenFilter.Side { get; set; }
+		bool? IEdgeNGramTokenFilter.PreserveOriginal { get; set; }
 
-		/// <inheritdoc />
+		/// <inheritdoc cref="IEdgeNGramTokenFilter.MinGram" />
 		public EdgeNGramTokenFilterDescriptor MinGram(int? minGram) => Assign(minGram, (a, v) => a.MinGram = v);
 
-		/// <inheritdoc />
+		/// <inheritdoc cref="IEdgeNGramTokenFilter.MaxGram" />
 		public EdgeNGramTokenFilterDescriptor MaxGram(int? maxGram) => Assign(maxGram, (a, v) => a.MaxGram = v);
 
-		/// <inheritdoc />
+		/// <inheritdoc cref="IEdgeNGramTokenFilter.Side" />
 		public EdgeNGramTokenFilterDescriptor Side(EdgeNGramSide? side) => Assign(side, (a, v) => a.Side = v);
+
+		/// <inheritdoc cref="IEdgeNGramTokenFilter.PreserveOriginal" />
+		public EdgeNGramTokenFilterDescriptor PreserveOriginal(bool? preserveOriginal = true) =>
+			Assign(preserveOriginal, (a, v) => a.PreserveOriginal = v);
 	}
 }

tests/Tests/Analysis/TokenFilters/TokenFilterTests.cs

@@ -98,6 +98,18 @@ public class EdgeNgramTests : TokenFilterAssertionBase<EdgeNgramTests>
 			public override string Name => "etf";
 		}
 
+		[SkipVersion("<7.8.0", "PreserveOriginal introduced in 7.8.0")]
+		public class EdgeNgramPreserveOriginalTests : TokenFilterAssertionBase<EdgeNgramPreserveOriginalTests>
+		{
+			public override FuncTokenFilters Fluent => (n, tf) => tf
+				.EdgeNGram(n, t => t.MaxGram(2).MinGram(1).PreserveOriginal());
+
+			public override ITokenFilter Initializer => new EdgeNGramTokenFilter { MaxGram = 2, MinGram = 1, PreserveOriginal = true };
+
+			public override object Json => new { type = "edge_ngram", min_gram = 1, max_gram = 2, preserve_original = true };
+			public override string Name => "etfpo";
+		}
+
 		public class ElisionTests : TokenFilterAssertionBase<ElisionTests>
 		{
 			public override FuncTokenFilters Fluent => (n, tf) => tf.Elision(n, t => t.Articles("a", "b", "c").ArticlesCase());