Fix IndexOutOfRangeException when parsing markdown tables without trailing pipes

src/Libraries/Microsoft.Extensions.DataIngestion.Markdig/MarkdownParser.cs

@@ -244,8 +244,11 @@ private static IngestionDocumentSection MapQuoteBlock(QuoteBlock quoteBlock, boo
     {
         int firstRowIndex = SkipFirstRow(table, outputContent) ? 1 : 0;
 
-        // For some reason, table.ColumnDefinitions.Count returns one extra column.
-        var cells = new IngestionDocumentElement?[table.Count - firstRowIndex, table.ColumnDefinitions.Count - 1];
+        // Calculate the actual number of columns by examining the rows.
+        // table.ColumnDefinitions.Count can vary: for tables WITH trailing pipes it's (columns + 1),
+        // but for tables WITHOUT trailing pipes it's equal to the actual column count.
+        int columnCount = GetColumnCount(table, firstRowIndex);
+        var cells = new IngestionDocumentElement?[table.Count - firstRowIndex, columnCount];
 
         for (int rowIndex = firstRowIndex; rowIndex < table.Count; rowIndex++)
         {
@@ -271,6 +274,25 @@ private static IngestionDocumentSection MapQuoteBlock(QuoteBlock quoteBlock, boo
 
         return cells;
 
+        static int GetColumnCount(Table table, int firstRowIndex)
+        {
+            int maxColumns = 0;
+            for (int rowIndex = firstRowIndex; rowIndex < table.Count; rowIndex++)
+            {
+                var tableRow = (TableRow)table[rowIndex];
+                int columnCount = 0;
+                for (int cellIndex = 0; cellIndex < tableRow.Count; cellIndex++)
+                {
+                    var tableCell = (TableCell)tableRow[cellIndex];
+                    columnCount += tableCell.ColumnSpan;
+                }
+
+                maxColumns = Math.Max(maxColumns, columnCount);
+            }
+
+            return maxColumns;
+        }
+
         // Some parsers like MarkItDown include a row with invalid markdown before the separator row:
         // |  |  |  |  |
         // | --- | --- | --- | --- |

test/Libraries/Microsoft.Extensions.DataIngestion.Tests/Readers/MarkdownReaderTests.cs

@@ -59,6 +59,47 @@ public override async Task SupportsTables()
         Assert.Equal(expected, documentTable.Cells.Map(element => element!.GetMarkdown().Trim()));
     }
 
+    [ConditionalFact]
+    public async Task SupportsTablesWithoutTrailingPipes()
+    {
+        // Markdown tables without trailing pipes (|) at the end of each row should be parsed correctly.
+        // This was causing IndexOutOfRangeException before the fix.
+        string markdownContent = """
+        # ReadyToRun Flags
+
+        | Flag                                       |      Value | Description
+        |:-------------------------------------------|-----------:|:-----------
+        | READYTORUN_FLAG_PLATFORM_NEUTRAL_SOURCE    | 0x00000001 | Set if the original IL image was platform neutral.
+        | READYTORUN_FLAG_COMPOSITE                  | 0x00000002 | The image represents a composite R2R file.
+        | READYTORUN_FLAG_PARTIAL                    | 0x00000004 |
+        | READYTORUN_FLAG_NONSHARED_PINVOKE_STUBS    | 0x00000008 | PInvoke stubs compiled into image are non-shareable.
+        | READYTORUN_FLAG_EMBEDDED_MSIL              | 0x00000010 | Input MSIL is embedded in the R2R image.
+        | READYTORUN_FLAG_COMPONENT                  | 0x00000020 | This is a component assembly of a composite R2R image
+        | READYTORUN_FLAG_MULTIMODULE_VERSION_BUBBLE | 0x00000040 | This R2R module has multiple modules within its version bubble.
+        | READYTORUN_FLAG_UNRELATED_R2R_CODE         | 0x00000080 | This R2R module has code in it that would not be naturally encoded.
+        | READYTORUN_FLAG_PLATFORM_NATIVE_IMAGE      | 0x00000100 | The owning composite executable is in the platform native format
+        """;
+
+        IngestionDocument document = await ReadAsync(markdownContent);
+
+        IngestionDocumentTable documentTable = Assert.Single(document.EnumerateContent().OfType<IngestionDocumentTable>());
+        Assert.Equal(10, documentTable.Cells.GetLength(0)); // 10 rows (1 header + 9 data rows)
+        Assert.Equal(3, documentTable.Cells.GetLength(1));  // 3 columns
+
+        // Verify a few key cells
+        Assert.Equal("Flag", documentTable.Cells[0, 0]!.GetMarkdown().Trim());
+        Assert.Equal("Value", documentTable.Cells[0, 1]!.GetMarkdown().Trim());
+        Assert.Equal("Description", documentTable.Cells[0, 2]!.GetMarkdown().Trim());
+
+        Assert.Equal("READYTORUN_FLAG_PLATFORM_NEUTRAL_SOURCE", documentTable.Cells[1, 0]!.GetMarkdown().Trim());
+        Assert.Equal("0x00000001", documentTable.Cells[1, 1]!.GetMarkdown().Trim());
+        Assert.Contains("platform neutral", documentTable.Cells[1, 2]!.GetMarkdown().Trim());
+
+        Assert.Equal("READYTORUN_FLAG_PARTIAL", documentTable.Cells[3, 0]!.GetMarkdown().Trim());
+        Assert.Equal("0x00000004", documentTable.Cells[3, 1]!.GetMarkdown().Trim());
+        Assert.Null(documentTable.Cells[3, 2]); // Empty description cell is null
+    }
+
     [ConditionalFact]
     public override async Task SupportsImages()
     {