Proposal: syntax for table cell spanning

[main-kun]

Introduction

The purpose of this proposal is to extend table syntax with support for column and row spans. Major inspiration for this proposal is doxygen markdown table syntax. The aim is to provide a simple and intuitive way to create complex tables with minimal syntax overhead.

Syntax

^ - placed as the only content within a table cell signifies an increase in rowspan for the cell above
> - placed as the only content within a table cell signifies an increase in colspan for the cell to the left

Multiple spans can be added up.

#|
|| Text ||
|| ^ ||
|| ^ ||
|| ^ ||
#|

should produce a cell spanning 4 rows. Similarly, multiple > cells in succession will produce a cell spanning n+1 columns, where n is the number of > cells.

Whitespace is not significant, | ^ |= |^| and | > | = |>|.

It's possible to escape these characters, \> and \^ render a normal table cell with corresponding characters.

Examples

Basic rowspan

Markdown input

#|
|| **Heading1** | **Heading2** ||
|| Text1 | Text2 ||
|| ^ | Text3||
|#

Rendered HTML

Heading1	Heading2
Text1	Text2
	Text3

Basic colspan

Markdown input

#|
|| **Heading1** | **Heading2** ||
|| Text1 | Text2 ||
|| Text3 |>||
|#

Rendered HTML

Heading1	Heading2
Text1	Text2
Text3

Mixed colspan and rowspan

Markdown input

#|
|| **Heading1** | **Heading2** | **Heading3**||
|| Text1 | Text2 | Text3||
|| Text4 |>| Text5 ||
|| ^ |>| Text 6 ||
|| Text 7 | Text8 | Text9 ||
|#

Rendered HTML

Heading1	Heading2	Heading3
Text1	Text2	Text3
Text4		Text5
		Text6
Text7	Text8	Text9

Edge cases

Mismatched spans

If a rowspan does not have a corresponding colspan, it can result in broken table layout. For instance:

#|
|| **Heading1** | **Heading2** | **Heading3**||
|| Text1 | Text2 | Text 3||
|| Text4 |>| Text5 ||
|| ^ | Text7 | Text 8 ||
|| Text 9 | Text10 | Text11 ||
|#

This markdown can be interpreted as a broken table with an excess cell:

Heading1	Heading2	Heading3
Text1	Text2	Text3
Text4		Text5
		Text6	Text7
Text8	Text9	Text10

To avoid this issue we can let the user know that the spans need to match in such cases, or render the table as plaintext to indicate that the table syntax is broken.