From 1d0fc8a8d2a1c22c5cfb6a0ec4daf81551cb00af Mon Sep 17 00:00:00 2001
From: Dmitry Gusarov <1462777+gusarov@users.noreply.github.com>
Date: Sat, 3 Oct 2020 17:48:40 -0400
Subject: [PATCH] Fix zero length matches

---
 Grepl.Tests/Commands/BasicCommands.cs | 19 +++++++++++++++++++
 Grepl/Executor.cs                     |  4 ++++
 2 files changed, 23 insertions(+)

diff --git a/Grepl.Tests/Commands/BasicCommands.cs b/Grepl.Tests/Commands/BasicCommands.cs
index 775eb23..76aca70 100644
--- a/Grepl.Tests/Commands/BasicCommands.cs
+++ b/Grepl.Tests/Commands/BasicCommands.cs
@@ -627,5 +627,24 @@ public void Should_30_show_only_file_name_replace_save()
 
 		}
 
+		[TestMethod]
+		public void Should_10_exclude_zero_length_match()
+		{
+			File.WriteAllText("test.txt", "abc\n");
+
+			var r = GreplEntry(".*", "-r");
+			Assert.AreEqual(0, r.Code);
+
+			var raw = r.Output;
+			var exp = @"
+test.txt
+abc
+";
+
+			CompareDetails(exp, raw);
+
+			Assert.AreEqual(exp, raw);
+
+		}
 	}
 }
diff --git a/Grepl/Executor.cs b/Grepl/Executor.cs
index d34f733..5e2d402 100644
--- a/Grepl/Executor.cs
+++ b/Grepl/Executor.cs
@@ -269,6 +269,10 @@ void Process(string file, bool printFileName, Dictionary<ColoredMessage, Capture
 				// var currentlnStart = -2; // initially unknown
 				foreach (Match match in matches)
 				{
+					if (match.Length == 0)
+					{
+						continue; // ignore zero-length matches and prevent index out of range when index >= length (zero length match at the end of a string)
+					}
 					// find the start of the line
 					var lineStart = body.LastIndexOf('\n', match.Index);
 					lineStart++;