CsvFieldIndexer: Fix handling of escaped characters

CsvLib.Tests/CsvFieldIndexerTests.cs

@@ -140,6 +140,66 @@ public class CsvFieldIndexerTests
         Assert.Equal(29, indexer.FieldIndex[1][3]);
     }
 
+    [Fact]
+    public void GenerateIndex__TwoLinesWithOneQuotedColumnsWithEscapedQuotes__TwoRows()
+    {
+        // --- Arrange
+        StringReader sr = new(
+            """
+            "Hello \"World\""
+            "Hello \"World\""
+            """);
+
+        // --- Act
+        CsvFieldIndexer indexer = new();
+        indexer.GenerateIndex(sr);
+
+        // --- Assert
+
+        Assert.Equal(3, indexer.Index.Count);
+        Assert.Equal(0, indexer.Index[0]);
+        Assert.Equal(18, indexer.Index[1]);
+        Assert.Equal(36, indexer.Index[2]);
+
+        Assert.Equal(2, indexer.FieldIndex.Count);
+        Assert.Equal(2, indexer.FieldIndex[0].Count);
+        Assert.Equal(1, indexer.FieldIndex[0][0]);
+        Assert.Equal(15, indexer.FieldIndex[0][1]);
+        Assert.Equal(2, indexer.FieldIndex[1].Count);
+        Assert.Equal(19, indexer.FieldIndex[1][0]);
+        Assert.Equal(33, indexer.FieldIndex[1][1]);
+    }
+
+    [Fact]
+    public void GenerateIndex__TwoLinesWithOneQuotedColumnsWithManyEscapedQuotes__TwoRows()
+    {
+        // --- Arrange
+        StringReader sr = new(
+            """
+            "Hello \"World\""
+            "Hello \"World\"\"\""
+            """);
+
+        // --- Act
+        CsvFieldIndexer indexer = new();
+        indexer.GenerateIndex(sr);
+
+        // --- Assert
+
+        Assert.Equal(3, indexer.Index.Count);
+        Assert.Equal(0, indexer.Index[0]);
+        Assert.Equal(18, indexer.Index[1]);
+        Assert.Equal(40, indexer.Index[2]);
+
+        Assert.Equal(2, indexer.FieldIndex.Count);
+        Assert.Equal(2, indexer.FieldIndex[0].Count);
+        Assert.Equal(1, indexer.FieldIndex[0][0]);
+        Assert.Equal(15, indexer.FieldIndex[0][1]);
+        Assert.Equal(2, indexer.FieldIndex[1].Count);
+        Assert.Equal(19, indexer.FieldIndex[1][0]);
+        Assert.Equal(37, indexer.FieldIndex[1][1]);
+    }
+
     [Fact]
     public void GenerateIndex__TwoLinesWithTwoQuotedColumnsWithUnicode__TwoRowsTwoFields()
     {

CsvLib.Tests/CsvParserTest.cs

@@ -36,7 +36,6 @@ public class CsvParserTest
         Assert.Equal("Hello World", parser.Data[0][0]);
     }
 
-
     [Fact]
     public void Parse__TwoLinesOfPainText__TwoRows()
     {
@@ -105,6 +104,50 @@ public class CsvParserTest
         Assert.Equal("World", parser.Data[1][1]);
     }
 
+    [Fact]
+    public void Parse__TwoLinesWithOneQuotedColumnsWithEscapedQuotes__TwoRows()
+    {
+        // --- Arrange
+        StringReader sr = new(
+            """
+            "Hello \"World\""
+            "Hello \"World\""
+            """);
+
+        // --- Act
+        CsvParser parser = new();
+        parser.Parse(sr);
+
+        // --- Assert
+        Assert.Equal(2, parser.Data.Count);
+        Assert.Single(parser.Data[0]);
+        Assert.Equal("Hello \"World\"", parser.Data[0][0]);
+        Assert.Single(parser.Data[1]);
+        Assert.Equal("Hello \"World\"", parser.Data[1][0]);
+    }
+
+    [Fact]
+    public void Parse__TwoLinesWithOneQuotedColumnsWithManyEscapedQuotes__TwoRows()
+    {
+        // --- Arrange
+        StringReader sr = new(
+            """
+            "Hello \"World\""
+            "Hello \"World\"\"\""
+            """);
+
+        // --- Act
+        CsvParser parser = new();
+        parser.Parse(sr);
+
+        // --- Assert
+        Assert.Equal(2, parser.Data.Count);
+        Assert.Single(parser.Data[0]);
+        Assert.Equal("Hello \"World\"", parser.Data[0][0]);
+        Assert.Single(parser.Data[1]);
+        Assert.Equal("Hello \"World\"\"\"", parser.Data[1][0]);
+    }
+
     [Fact]
     public void GenerateIndex__TwoLinesWithTwoQuotedColumnsWithUnicode__TwoRowsTwoFields()
     {

CsvLib/CsvFieldIndexer.cs

@@ -102,6 +102,9 @@ public class CsvFieldIndexer
             else if (c == _escapeChar && _insideString)
             {
                 i++;
+                long absolutePosition = lineOffset + i + unicodeDelta;
+                fieldStartPosition ??= absolutePosition;
+                fieldEndPosition = absolutePosition;
             }
             else if ((c == '\n' || c == '\r') && _insideString == false)
             {