no syntax to create line_block (hardbreak creates paragraph with raw linebreaks) #899
Description
What version of myst-parser are you using?
2.0.0
What version dependencies are you using?
docutils==0.20.1
sphinx==7.2.6
What operating system are you using?
Linux
Describe the Bug
MyST parser does not have proper syntax for line-block and emulates line-block by creating paragraph with hardbreaks (indicated by \ followed by linebreak). This introduces incompatibility in some (perhaps uncommon, but valid) cases. One of them is table with line-block:
# Test text block inside list-table
## list-table
```{list-table}
* - A1
- B1 \
in \
3 lines
* - A2
- B2
```
## list-table via eval-rst
```{eval-rst}
.. list-table::
* - A1
- | B1
| in
| 3 lines
* - A2
- B2
```
The first table will be rendered incorrectly (as the B1 cell is a paragraph node with newlines inserted as raw latex \\ which has a different meaning inside table; whereas RST will process line_block node inside table with lines correctly).
The pseudoXML is here:
<document source="/home/eudoxos/temp/myst-br/index.md" translation_progress="{'total': 0, 'translated': 0}" xmlns:c="https://www.sphinx-doc.org/" xmlns:changeset="https://www.sphinx-doc.org/" xmlns:citation="https://www.sphinx-doc.org/" xmlns:cpp="https://www.sphinx-doc.org/" xmlns:index="https://www.sphinx-doc.org/" xmlns:js="https://www.sphinx-doc.org/" xmlns:math="https://www.sphinx-doc.org/" xmlns:py="https://www.sphinx-doc.org/" xmlns:rst="https://www.sphinx-doc.org/" xmlns:std="https://www.sphinx-doc.org/">
<section ids="test-text-block-inside-list-table" names="test\ text\ block\ inside\ list-table">
<title>
Test text block inside list-table
<section ids="list-table" names="list-table">
<title>
list-table
<table>
<tgroup cols="2">
<colspec colwidth="50">
<colspec colwidth="50">
<tbody>
<row>
<entry>
<paragraph>
A1
<entry>
<paragraph>
B1
<raw format="html" xml:space="preserve">
<br />
<raw format="latex" xml:space="preserve">
\\
in
<raw format="html" xml:space="preserve">
<br />
<raw format="latex" xml:space="preserve">
\\
3 lines
<row>
<entry>
<paragraph>
A2
<entry>
<paragraph>
B2
<section ids="list-table-via-eval-rst" names="list-table\ via\ eval-rst">
<title>
list-table via eval-rst
<table>
<tgroup cols="2">
<colspec colwidth="50">
<colspec colwidth="50">
<tbody>
<row>
<entry>
<paragraph>
A1
<entry>
<line_block>
<line>
B1
<line>
in
<line>
3 lines
<row>
<entry>
<paragraph>
A2
<entry>
<paragraph>
B2
Expected Behavior
(proposed behavior:) paragraph with hardbreaks and no softbreaks would be converted to line_block. Paragraph mixing hardbreaks and softbreaks would trigger warning. Paragraphs with softbreak only are just paragraphs.
Or alternatively, document another way of creating line_block in MyST (I did not find one).
To Reproduce
Compile the above source (saved as index.md) with this minimal conf.py:
project="test"
extensions=['myst_parser']