[rahul05ranjan]

What

tablefmt="mediawiki" writes cell and header values raw, so any literal | silently splits the cell into extra columns when the table is rendered on a MediaWiki wiki — || is the column separator in data rows, !! in header rows:

>>> print(tabulate.tabulate([["x | y"], ["a || b"]], headers=["h | 1"], tablefmt="mediawiki"))
{| class="wikitable" style="text-align: left;"
|+ <!-- caption -->
|-
! h | 1          <- header gains a spurious empty column
|-
| x | y          <- becomes two cells
|-
| a || b         <- becomes three cells
|}

The data is silently corrupted. This is the same class the github/pipe formats already handle for their separator (they render x | y as x \| y), and the same class prettytable fixed for its own MediaWiki emitter (prettytable #544, | → |).

Fixes #499

Fix

_mediawiki_row_with_attrs now escapes cell values before joining them: | → | everywhere, and ! → ! in header rows (where !! is the separator). Values without pipes/bangs are byte-identical to before. Newlines inside cells are deliberately untouched — multiline mediawiki support is already on the maintainer's TODO list and would use <br />.

Verification

Two new tests (test_mediawiki_escapes_pipes_in_cells_and_headers, test_mediawiki_escapes_bang_in_headers) fail on master and pass with this change; the existing test_mediawiki/test_mediawiki_headerless pins are unchanged. Full suite: python3 -m pytest test/ → 351 passed, 17 skipped, zero failures.