[Bug] Fix Malformed Table Crash

HISTORY.rst

@@ -12,7 +12,7 @@ Release History
 
 **Fixes**
 
-- None
+- Fixes `#70 <https://github.com/dfop02/html4docx/issues/70>`_: malformed table overflow. | `dfop02 <https://github.com/dfop02>`_
 
 **New Features**
 

html4docx/h4d.py

@@ -1281,9 +1281,14 @@ def handle_table(self, current_attrs):
         for cell_row, row in enumerate(self.get_table_rows(table_soup)):
             col_offset = 0  # Shift index if some columns are occupied
             for col in self.get_table_columns(row):
-                while used_cells[cell_row][col_offset]:
+                while col_offset < cols and used_cells[cell_row][col_offset]:
                     col_offset += 1
 
+                if col_offset >= cols:
+                    raise ValueError(
+                        f"Table layout mismatch: exceeded column count ({cols}) at row {cell_row}"
+                    )
+
                 current_row = cell_row
                 current_col = col_offset
 
@@ -1782,20 +1787,46 @@ def get_table_dimensions(self, table_soup):
 
         default_span = 1
         max_cols = 0
-        max_rows = len(rows)
+
+        # Track occupied cells caused by rowspan
+        used_cells = []
 
         for row_idx, row in enumerate(rows):
             cols = self.get_table_columns(row)
-            # Handle colspan
-            row_col_count = sum(utils.safe_int(col.get('colspan', default_span)) for col in cols)
-            max_cols = max(max_cols, row_col_count)
 
-            # Handle rowspan
+            # Ensure used_cells has current row
+            while len(used_cells) <= row_idx:
+                used_cells.append([])
+
+            col_offset = 0
+
             for col in cols:
+                # Expand row if needed
+                while len(used_cells[row_idx]) <= col_offset:
+                    used_cells[row_idx].append(False)
+
+                # Skip already occupied cells
+                while col_offset < len(used_cells[row_idx]) and used_cells[row_idx][col_offset]:
+                    col_offset += 1
+
                 rowspan = utils.safe_int(col.get('rowspan', default_span))
-                if rowspan > default_span:
-                    max_rows = max(max_rows, row_idx + rowspan)
+                colspan = utils.safe_int(col.get('colspan', default_span))
+
+                # Mark occupied cells
+                for r in range(row_idx, row_idx + rowspan):
+                    while len(used_cells) <= r:
+                        used_cells.append([])
+
+                    for c in range(col_offset, col_offset + colspan):
+                        while len(used_cells[r]) <= c:
+                            used_cells[r].append(False)
+                        used_cells[r][c] = True
+
+                col_offset += colspan
+
+            max_cols = max(max_cols, len(used_cells[row_idx]))
 
+        max_rows = len(used_cells)
         return max_rows, max_cols
 
     def get_tables(self) -> None:

tests/test_h4d.py

@@ -2055,6 +2055,56 @@ def test_extreme_colspan_rowspan_cases(self):
         except Exception as e:
             self.fail(f"Processing extreme table failed with unexpected error: {e}")
 
+    def test_malformed_table_overflow(self):
+        """Test table where rowspan or colspan causes column overflow beyond initial dimension calculation"""
+        self.document.add_heading('Test: Malformed Table Overflow', level=1)
+
+        malformed_html = """
+        <table>
+        <tr>
+            <td rowspan="2">spans down</td>
+            <td>B1</td>
+        </tr>
+        <tr>
+            <td>A2</td>
+            <td>B2</td>
+        </tr>
+        </table>
+        """
+
+        try:
+            self.parser.table_style = 'Table Grid'
+            self.parser.add_html_to_document(malformed_html, self.document)
+            document = self.parser.parse_html_string(malformed_html)
+
+            tables = document.tables
+            assert len(tables) == 1, "Should create exactly one table"
+
+            table = tables[0]
+
+            assert len(table.columns) == 3, (
+                f"Expected 3 columns due to rowspan shift, but got {len(table.columns)}"
+            )
+
+            assert len(table.rows) == 2, (
+                f"Expected 2 rows, but got {len(table.rows)}"
+            )
+
+            # Validate content placement
+            assert "spans down" in table.cell(0, 0).text, "Rowspan cell not in correct position"
+            assert "B1" in table.cell(0, 1).text, "B1 should be in row 0, col 1"
+
+            # Second row:
+            # col 0 is occupied by rowspan
+            # so A2 → col 1, B2 → col 2
+            assert "A2" in table.cell(1, 1).text, "A2 should be shifted to column 1"
+            assert "B2" in table.cell(1, 2).text, "B2 should be in column 2"
+
+        except IndexError as e:
+            self.fail(f"Malformed table caused IndexError (regression): {e}")
+        except Exception as e:
+            self.fail(f"Malformed table failed with unexpected error: {e}")
+
     def test_nested_styles_on_multiple_tags(self):
         """ Test nested styles on multiple tags """
         self.document.add_heading('Test: Test nested styles on multiple tags', level=1)