Markdown does not render correctly when used inside a Django @stringfilter

[marcin-wicha]

Describe the bug

Markdown is not correctly rendered when the package is used inside a string filter in Django.
Lists error out with Int() being passed characters, when I disable the "lists" rule, markdown parses through but it's missing first letter at new lines.

To Reproduce

Steps to reproduce the behavior:

1. Create a string filter in Django with markdown-it.

from django import template
from django.template.defaultfilters import stringfilter, linebreaks_filter
from django.utils.safestring import mark_safe
from django.conf import settings
from markdown_it import MarkdownIt

register = template.Library()

@register.filter()
@stringfilter
def format_text(text):
    if settings.RICH_TEXT_ENABLED:
        return parse_markdown(text)
    else:
        return linebreaks_filter(text)

def parse_markdown(text):
    md = MarkdownIt()
    html = md.render(text)
    return mark_safe(html)

2. Use the string filter on your site.
3. See error

Expected behavior

Source:

---
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  resize in browser.
- __[babelfish](https://github.com/nodeca/babelfish/)__ - developer friendly
  i18n with plurals support and easy syntax.

You will like those projects!

---

# h1 Heading 8-)
## h2 Heading
### h3 Heading
#### h4 Heading
##### h5 Heading
###### h6 Heading

Log:

Request Method: | GET
-- | --
http://localhost:8000/sprawy/sprawa-5/
2.2.16
ValueError
invalid literal for int() with base 10: 't'
/usr/local/lib/python3.7/site-packages/markdown_it/rules_block/list.py in list_block, line 139
/usr/local/bin/python
3.7.9
['/code',  '/usr/local/lib/python37.zip',  '/usr/local/lib/python3.7',  '/usr/local/lib/python3.7/lib-dynload',  '/usr/local/lib/python3.7/site-packages',  '/usr/local/lib/python3.7/site-packages/odf',  '/usr/local/lib/python3.7/site-packages/odf',  '/usr/local/lib/python3.7/site-packages/odf',  '/usr/local/lib/python3.7/site-packages/odf',  '/usr/local/lib/python3.7/site-packages/odf',  '/usr/local/lib/python3.7/site-packages/odf',  '/usr/local/lib/python3.7/site-packages/odf']
Czw, 8 Paź 2020 21:03:30 +0200

Environment

• Python Version [3.7.9]

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[chrisjsewell]

Heya,

Is there a way to debug what text is actually being parsed to parse_markdown, i.e. is django altering the text in any way before it reaches parse_markdown?

Because, the text you supplied seems to run fine through markdown-it-py:

$ markdown-it 
markdown-it-py [version 0.5.5] (interactive)
Type Ctrl-D to complete input, or Ctrl-C to exit.
>>> ---
__Advertisement :)__

- __[pica](https://nodeca.github.io/pica/demo/)__ - high quality and fast image
  resize in browser.
- __[babelfish](https://github.com/nodeca/babelfish/)__ - developer friendly
  i18n with plurals support and easy syntax.

You will like those projects!

---

# h1 Heading 8-)
## h2 Heading
### h3 Heading
#### h4 Heading
##### h5 Heading
###### h6 Heading... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 
... 
... ^D
<hr />
<p><strong>Advertisement :)</strong></p>
<ul>
<li>
<p><strong><a href="https://nodeca.github.io/pica/demo/">pica</a></strong> - high quality and fast image</p>
<p>resize in browser.</p>
</li>
<li>
<p><strong><a href="https://github.com/nodeca/babelfish/">babelfish</a></strong> - developer friendly</p>
<p>i18n with plurals support and easy syntax.</p>
</li>
</ul>
<p>You will like those projects!</p>
<hr />
<h1>h1 Heading 8-)</h1>
<h2>h2 Heading</h2>
<h3>h3 Heading</h3>
<h4>h4 Heading</h4>
<h5>h5 Heading</h5>
<h6>h6 Heading</h6>
>>> 

but it's missing first letter at new lines.

Perhaps this is some issue with newline characters.
What operating system are you working on?

[marcin-wicha]

OS: Windows 10
Let me try out OSX as well, to see if there's a difference.

I've tried different Markdown parsers before (Markdown, markdown2, Mistune) and they worked without a problem.
I wanted to go for markdown-it for security stance and found this weird behaviour :)

That's the console output of text passed into parse_markdown.

web_1   | ---
web_1   | __Advertisement :)__
web_1   |
web_1   | - __[pica](https://nodeca.github.io/pica/demo/)__ - high quality and fast image
web_1   |   resize in browser.
web_1   | - __[babelfish](https://github.com/nodeca/babelfish/)__ - developer friendly   
web_1   |   i18n with plurals support and easy syntax.
web_1   |
web_1   | You will like those projects!
web_1   |    
web_1   | ---
web_1   |    
web_1   | # h1 Heading 8-)
web_1   | ## h2 Heading
web_1   | ### h3 Heading
web_1   | #### h4 Heading
web_1   | ##### h5 Heading
web_1   | ###### h6 Heading

edit:
On OSX with disabled lists.