Fix NullReferenceException for empty headers (#69)

* Add reader tests for empty header rows

* Fix NullReferenceException for empty header rows

Author: saulm314

src/CSVReader.cs

@@ -334,7 +334,7 @@ public CSVReader(StreamReader source, CSVSettings settings = null)
             if (_settings.HeaderRowIncluded)
             {
                 var line = source.ReadLine();
-                if (_settings.AllowSepLine)
+                if (line != null && _settings.AllowSepLine)
                 {
                     var newDelimiter = CSV.ParseSepLine(line);
                     if (newDelimiter != null)
@@ -345,7 +345,7 @@ public CSVReader(StreamReader source, CSVSettings settings = null)
                     }
                 }
 
-                Headers = CSV.ParseLine(line, _settings);
+                Headers = CSV.ParseLine(line, _settings) ?? Array.Empty<string>();
             }
             else
             {
@@ -371,7 +371,7 @@ public CSVReader(Stream source, CSVSettings settings = null)
             if (_settings.HeaderRowIncluded)
             {
                 var line = _stream.ReadLine();
-                if (_settings.AllowSepLine)
+                if (line != null && _settings.AllowSepLine)
                 {
                     var newDelimiter = CSV.ParseSepLine(line);
                     if (newDelimiter != null)
@@ -382,7 +382,7 @@ public CSVReader(Stream source, CSVSettings settings = null)
                     }
                 }
 
-                Headers = CSV.ParseLine(line, _settings);
+                Headers = CSV.ParseLine(line, _settings) ?? Array.Empty<string>();
             }
             else
             {

tests/BasicParseTests.cs

@@ -185,6 +185,8 @@ public void ParseSepLineTest()
             Assert.AreEqual(',', CSV.ParseSepLine("sep=,"));
             Assert.AreEqual(',', CSV.ParseSepLine("sep = ,"));
             Assert.AreEqual(null, CSV.ParseSepLine("sep="));
+            Assert.AreEqual(null, CSV.ParseSepLine("sep=   "));
+            Assert.AreEqual(null, CSV.ParseSepLine("sep    =   "));
             Assert.Throws<Exception>(() =>
             {
                 CSV.ParseSepLine("sep= this is a test since separators can't be more than a single character");

tests/ReaderTest.cs

@@ -375,6 +375,145 @@ public void TestIssue62()
             Assert.AreEqual(desiredLines, outputLines);
         }
 
+        [Test]
+        public void TestEmptyHeaderRow()
+        {
+            var settings = new CSVSettings()
+            {
+                LineSeparator = "\n",
+                FieldDelimiter = ',',
+                HeaderRowIncluded = true
+            };
+
+            using (var cr = CSVReader.FromString("", settings))
+            {
+                Assert.AreEqual(0, cr.Headers.Length);
+                Assert.AreEqual(0, cr.Count());
+            }
+
+            using (var cr = CSVReader.FromString(" ", settings))
+            {
+                Assert.AreEqual(1, cr.Headers.Length);
+                Assert.AreEqual(" ", cr.Headers[0]);
+                Assert.AreEqual(0, cr.Count());
+            }
+
+            using (var cr = CSVReader.FromString("\t", settings))
+            {
+                Assert.AreEqual(1, cr.Headers.Length);
+                Assert.AreEqual("\t", cr.Headers[0]);
+                Assert.AreEqual(0, cr.Count());
+            }
+
+            using (var cr = CSVReader.FromString("\n", settings))
+            {
+                Assert.AreEqual(0, cr.Headers.Length);
+                Assert.AreEqual(0, cr.Count());
+            }
+
+            using (var cr = CSVReader.FromString(" \n", settings))
+            {
+                Assert.AreEqual(1, cr.Headers.Length);
+                Assert.AreEqual(" ", cr.Headers[0]);
+            }
+
+            using (var cr = CSVReader.FromString("\n ", settings))
+            {
+                Assert.AreEqual(0, cr.Headers.Length);
+                var lines = cr.ToArray();
+                Assert.AreEqual(1, lines.Length);
+                Assert.AreEqual(1, lines[0].Length);
+                Assert.AreEqual(" ", lines[0][0]);
+            }
+        }
+
+        [Test]
+        public void TestSepLineEmptyHeaderRow()
+        {
+            var settings = new CSVSettings()
+            {
+                LineSeparator = "\n",
+                FieldDelimiter = ',',
+                HeaderRowIncluded = true,
+                AllowSepLine = true
+            };
+
+            // if without an = sign, "sep" is just a header
+            using (var cr = CSVReader.FromString("sep", settings))
+            {
+                Assert.AreEqual(1, cr.Headers.Length);
+                Assert.AreEqual("sep", cr.Headers[0]);
+                Assert.AreEqual(0, cr.Count());
+            }
+
+            // if with an = sign but no character specified, then "sep=" is also treated as a header
+            // note that this is different from Excel's behaviour
+            // Excel interprets this as a field delimiter setter, but it doesn't set it to any character
+            // so all lines end up getting displayed in plaintext
+            using (var cr = CSVReader.FromString("sep=", settings))
+            {
+                Assert.AreEqual(1, cr.Headers.Length);
+                Assert.AreEqual("sep=", cr.Headers[0]);
+                Assert.AreEqual(0, cr.Count());
+            }
+
+            using (var cr = CSVReader.FromString("sep= ", settings))
+            {
+                Assert.AreEqual(1, cr.Headers.Length);
+                Assert.AreEqual("sep= ", cr.Headers[0]);
+                Assert.AreEqual(0, cr.Count());
+            }
+
+            using (var cr = CSVReader.FromString("sep = ", settings))
+            {
+                Assert.AreEqual(1, cr.Headers.Length);
+                Assert.AreEqual("sep = ", cr.Headers[0]);
+                Assert.AreEqual(0, cr.Count());
+            }
+
+            using (var cr = CSVReader.FromString("sep=;", settings))
+            {
+                Assert.AreEqual(0, cr.Headers.Length);
+                Assert.AreEqual(0, cr.Count());
+            }
+
+            using (var cr = CSVReader.FromString("sep=\n\nline1,line2", settings))
+            {
+                Assert.AreEqual(1, cr.Headers.Length);
+                Assert.AreEqual("sep=", cr.Headers[0]);
+                var lines = cr.ToArray();
+                Assert.AreEqual(2, lines.Length);
+                Assert.AreEqual(1, lines[0].Length);
+                Assert.AreEqual("", lines[0][0]);
+                Assert.AreEqual(2, lines[1].Length);
+                Assert.AreEqual("line1", lines[1][0]);
+                Assert.AreEqual("line2", lines[1][1]);
+            }
+
+            using (var cr = CSVReader.FromString("sep=;\n\nline1;line2", settings))
+            {
+                Assert.AreEqual(0, cr.Headers.Length);
+                var lines = cr.ToArray();
+                Assert.AreEqual(1, lines.Length);
+                Assert.AreEqual(2, lines[0].Length);
+                Assert.AreEqual("line1", lines[0][0]);
+                Assert.AreEqual("line2", lines[0][1]);
+            }
+
+            using (var cr = CSVReader.FromString("sep=\n", settings))
+            {
+                Assert.AreEqual(1, cr.Headers.Length);
+                Assert.AreEqual("sep=", cr.Headers[0]);
+                Assert.AreEqual(0, cr.Count());
+            }
+
+            using (var cr = CSVReader.FromString("sep=;\n", settings))
+            {
+                Assert.AreEqual(0, cr.Headers.Length);
+                Assert.AreEqual(0, cr.Count());
+            }
+        }
+
 #if HAS_ASYNC_IENUM
         [Test]
         public async Task TestAsyncReader()