Fix: Add leading and trailing pipes to markdown tables for GFM compliance

[PatD42]

Summary

Fixes #1731 - Adds leading and trailing pipe delimiters to markdown tables for GitHub Flavored Markdown (GFM) compliance.

List of files changed and why

• crawl4ai/html2text/__init__.py (lines 717-733) - Fixed table generation logic to always include boundary pipes
• tests/test_table_gfm_compliance.py - Added 8 comprehensive unit tests to verify GFM compliance

Changes

Before

Parameter | Guideline
---|---
Value1 | Value2

After

| Parameter | Guideline |
| --- | --- |
| Value1 | Value2 |

Technical Changes

1. Line 719: Removed condition to always output | for every cell (including first)
2. Line 726: Added self.o(" |") to close rows with trailing pipe
3. Line 731: Fixed separator format from ---|--- to | --- | --- |

Why This Fix (Not pad_tables=True)

• pad_tables=False is the default setting
• pad_tables is designed for column alignment, not structural GFM compliance
• Table generation should produce correct output by default
• This fix works with both pad_tables=True and False

How Has This Been Tested?

Unit Tests (8 tests covering all scenarios):

• ✅ test_table_has_leading_pipes - Verifies all rows start with |
• ✅ test_table_has_trailing_pipes - Verifies all rows end with |
• ✅ test_separator_row_has_pipes - Verifies separator format | --- | --- |
• ✅ test_works_with_pad_tables_false - Tests with default setting
• ✅ test_works_with_pad_tables_true - Tests with padding enabled
• ✅ test_multirow_table - Tests 4-row table with 3 columns
• ✅ test_single_column_table - Tests edge case
• ✅ test_empty_cells - Tests tables with empty cells

Manual Testing:

from crawl4ai.html2text import HTML2Text

html = '<table><tr><th>A</th><th>B</th></tr><tr><td>1</td><td>2</td></tr></table>'
h = HTML2Text()
result = h.handle(html)
print(result)
# Output: | A | B |
#         | --- | --- |
#         | 1 | 2 |

All tests verify that:

• Every table row has leading and trailing pipes
• Works with both pad_tables settings
• Handles edge cases (empty cells, single column, multi-row)

Impact

• ✅ GFM compliant tables
• ✅ Better parser compatibility (Jekyll, Hugo, CommonMark, showdown)
• ✅ Improved IDE/preview rendering
• ✅ No breaking changes (cosmetic improvement only)
• ✅ Works with both pad_tables settings

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (N/A - internal fix)
• I have added/updated unit tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes