Pasting a table that contains thead tag leads to column spanning issues

[bperson]

Describe the bug
Pasting a table that contains thead leads to column spanning issues: the first column defined in the thead will be spanned across all the columns defined in the tbody, any extra column in the thead are then appended as if they were "extra" columns. ( see the screenshots below, describing column spanning issues is a pain 😅 )

To Reproduce
Steps to reproduce the behavior:

1. Copy and Paste a table containing a thead tag ( for instance from a GitHub README )
2. The thead is preserved in the HTML with its children, but it creates layout / column spanning issues

Expected behavior
Either filter out the thead when copy-pasting
OR
Proper support of thead in tables

Screenshots

Desktop (please complete the following information):

• OS: macOS 10.13.4
• Browser Chrome
• Version 67.0.3396.99

Additional context
Tried on p2s and on frontenberg so, I'm guessing the latest?
It's potentially a duplicate of #6902

[designsimply]

Tested and confirmed with WordPress 4.9.6 and Gutenberg 3.1.1 using Safari 11.1.1 on macOS 10.13.5 with the following sample html:

<table>
<thead>
<tr>
<th>Acronym</th>
<th>Definition</th>
</tr>
</thead>
<tbody>
<tr>
<td>RC</td>
<td>Row Count</td>
</tr>
<tr>
<td>TS</td>
<td>Total Byte Size</td>
</tr></tbody></table>

^{Seen at http://alittletestblog.com/wp-admin/post.php?post=13878&action=edit running WordPress 4.9.6 and Gutenberg 3.1.1 using Safari 11.1.1 on macOS 10.13.5.}

^{Seen at http://alittletestblog.com/2018/07/05/thead-tag-test/ running WordPress 4.9.6 and Gutenberg 3.1.1 using Safari 11.1.1 on macOS 10.13.5.}

I noticed that <table> becomes <table class="wp-block-table"> and removing class="wp-block-table" from <table class="wp-block-table"> on the front end makes the column spanning issue go away.

[marcusig]

Just noticed the same issue in v3.3.0

The issue is here:

.wp-block-table tbody {
    width: 100%;
    display: table;
    min-width: 240px;
}

tbody display property shouldn't be set to table.

I think the best would be to leave the display property empty, or set it to the default table-row-group if really necessary.

[ianbelanger79]

PR #7899 fixes this issue so I am closing this one