Cell split over table boundary causes error with border-collapse: collapse

[aschmitz]

In WeasyPrint 54.0b1, rendering the following HTML gives an error:

<style>
  table {
    border-collapse: collapse;
  }
</style>

<div style="height: 24cm"></div>

<table><tr><td>
  a<br>
  a<br>
  a<br>
  a
</td></tr></table>

(You may have to adjust the height of the spacing div to force the table to split over the page boundary depending on your font.)

The error is an IndexError: list index out of range on line 856 of draw.py, as it tries to index in to vertical_borders past its length. It appears as though build.py's collapse_table_borders returns one more horizontal border than there are columns, but only as many vertical borders as there are rows.

I can fix the error by changing line 889 of draw.py to for y in range(grid_height - 1):, but I suspect the correct behavior may be to extend the output of collapse_table_borders for an additional row.

[aschmitz]

It appears adding this to your CSS is a temporary fix to revert back to the "pages can't split in the middle of a row" behavior from versions prior to 54:

td, th {
  break-inside: avoid;
}

(In particular, it appears as though tables breaking over the edge of a page are still not a problem, just rows.)

[liZe]

Thanks a lot for the bug report.

It’s now fixed, with many other use cases of tables with collapsed cells.