list-table: fix colspan in first row

Author: not-my-profile

list-table/expected.html

@@ -91,3 +91,16 @@
 </tr>
 </tbody>
 </table>
+<table>
+<thead>
+<tr class="header">
+<th colspan="2">header</th>
+</tr>
+</thead>
+<tbody>
+<tr class="odd">
+<td>cell 1</td>
+<td>cell 2</td>
+</tr>
+</tbody>
+</table>

list-table/list-table.lua

@@ -133,7 +133,12 @@ local function process(div)
     local header_col_count = tonumber(div.attr.attributes['header-cols']) or 0
     div.attr.attributes['header-cols'] = nil
 
-    local colspecs = get_colspecs(div.attr.attributes, #rows[1][2])
+    local column_count = 0
+    for i = 1, #rows[1][2] do
+        column_count = column_count + rows[1][2][i].col_span
+    end
+
+    local colspecs = get_colspecs(div.attr.attributes, column_count)
     local thead_rows = {}
     for i = 1, header_row_count do
         table.insert(thead_rows, table.remove(rows, 1))

list-table/sample.md

@@ -54,3 +54,9 @@
    * - reStructuredText
      - []{align=c} ` ``code`` `
 :::
+
+::: list-table
+*  - []{colspan=2}header
+*  - cell 1
+   - cell 2
+:::