Skip correctly empty lines while detecting delimiter, fixes #309 (#404)

* Skipping empty lines during guessDelimiter phase

Fixes #309

papaparse.js

@@ -878,7 +878,7 @@
 			_delimiterError = false;
 			if (!_config.delimiter)
 			{
-				var delimGuess = guessDelimiter(input, _config.newline);
+				var delimGuess = guessDelimiter(input, _config.newline, _config.skipEmptyLines);
 				if (delimGuess.successful)
 					_config.delimiter = delimGuess.bestDelimiter;
 				else
@@ -1040,7 +1040,7 @@
 			return _results;
 		}
 
-		function guessDelimiter(input, newline)
+		function guessDelimiter(input, newline, skipEmptyLines)
 		{
 			var delimChoices = [',', '\t', '|', ';', Papa.RECORD_SEP, Papa.UNIT_SEP];
 			var bestDelim, bestDelta, fieldCountPrevRow;
@@ -1048,7 +1048,7 @@
 			for (var i = 0; i < delimChoices.length; i++)
 			{
 				var delim = delimChoices[i];
-				var delta = 0, avgFieldCount = 0;
+				var delta = 0, avgFieldCount = 0, emptyLinesCount = 0;
 				fieldCountPrevRow = undefined;
 
 				var preview = new Parser({
@@ -1059,6 +1059,10 @@
 
 				for (var j = 0; j < preview.data.length; j++)
 				{
+					if (skipEmptyLines && preview.data[j].length === 1 && preview.data[j][0].length === 0) {
+						emptyLinesCount++
+						continue
+					}
 					var fieldCount = preview.data[j].length;
 					avgFieldCount += fieldCount;
 
@@ -1075,7 +1079,7 @@
 				}
 
 				if (preview.data.length > 0)
-					avgFieldCount /= preview.data.length;
+					avgFieldCount /= (preview.data.length - emptyLinesCount);
 
 				if ((typeof bestDelta === 'undefined' || delta < bestDelta)
 					&& avgFieldCount > 1.99)

tests/test-cases.js

@@ -919,6 +919,16 @@ var PARSE_TESTS = [
 			errors: []
 		}
 	},
+	{
+		description: "Skip empty lines while detecting delimiter",
+		notes: "Parsing correctly newline-terminated short data with delimiter:auto and skipEmptyLines:true",
+		input: 'a,b\n1,2\n3,4\n',
+		config: { header: true, skipEmptyLines: true },
+		expected: {
+			data: [{'a': '1', 'b': '2'}, {'a': '3', 'b': '4'}],
+			errors: []
+		}
+	},
 	{
 		description: "Single quote as quote character",
 		notes: "Must parse correctly when single quote is specified as a quote character",