From 739476ecdff4b210cb85cae724dc31db2be3a8c1 Mon Sep 17 00:00:00 2001
From: Eric Fossas <efossas@users.noreply.github.com>
Date: Mon, 7 May 2018 01:48:05 -0600
Subject: [PATCH] Ignore lines with comments when guessing delimiter (#503)

---
 papaparse.js        |  5 +++--
 tests/test-cases.js | 20 ++++++++++++++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/papaparse.js b/papaparse.js
index 4ee8de2..fa8611d 100755
--- a/papaparse.js
+++ b/papaparse.js
@@ -898,7 +898,7 @@
 			_delimiterError = false;
 			if (!_config.delimiter)
 			{
-				var delimGuess = guessDelimiter(input, _config.newline, _config.skipEmptyLines);
+				var delimGuess = guessDelimiter(input, _config.newline, _config.skipEmptyLines, _config.comments);
 				if (delimGuess.successful)
 					_config.delimiter = delimGuess.bestDelimiter;
 				else
@@ -1073,7 +1073,7 @@
 			return _results;
 		}
 
-		function guessDelimiter(input, newline, skipEmptyLines)
+		function guessDelimiter(input, newline, skipEmptyLines, comments)
 		{
 			var delimChoices = [',', '\t', '|', ';', Papa.RECORD_SEP, Papa.UNIT_SEP];
 			var bestDelim, bestDelta, fieldCountPrevRow;
@@ -1085,6 +1085,7 @@
 				fieldCountPrevRow = undefined;
 
 				var preview = new Parser({
+					comments: comments,
 					delimiter: delim,
 					newline: newline,
 					preview: 10
diff --git a/tests/test-cases.js b/tests/test-cases.js
index 773635e..b10c386 100644
--- a/tests/test-cases.js
+++ b/tests/test-cases.js
@@ -1090,6 +1090,26 @@ var PARSE_TESTS = [
 			errors: []
 		}
 	},
+	{
+		description: "Lines with comments are not used when guessing the delimiter in an escaped file",
+		notes: "Guessing the delimiter should work even if there are many lines of comments at the start of the file",
+		input: '#1\n#2\n#3\n#4\n#5\n#6\n#7\n#8\n#9\n#10\none,"t,w,o",three\nfour,five,six',
+		config: { comments: '#' },
+		expected: {
+			data: [['one','t,w,o','three'],['four','five','six']],
+			errors: []
+		}
+	},
+	{
+		description: "Lines with comments are not used when guessing the delimiter in a non-escaped file",
+		notes: "Guessing the delimiter should work even if there are many lines of comments at the start of the file",
+		input: '#1\n#2\n#3\n#4\n#5\n#6\n#7\n#8\n#9\n#10\n#11\none,two,three\nfour,five,six',
+		config: { comments: '#' },
+		expected: {
+			data: [['one','two','three'],['four','five','six']],
+			errors: []
+		}
+	},
 	{
 		description: "Single quote as quote character",
 		notes: "Must parse correctly when single quote is specified as a quote character",