Nested ordered lists cause incorrectly affect the parent ordered list's numbering

[MH-ZShearer]

WeasyPrint Version: 56.1
OS: Windows 10 21H2 (19044.2130)
Python: 3.10.5

With the following HTML, WeasyPrint doesn't generate the expected output

<ol type="a">
    <li>(a.) Item 1</li>
    <li>(b.) Item 2</li>
    <ol type="1">
      <li>(1.) Item 2.1</li>
      <li>(2.) Item 2.2</li>
      <li>(3.) Item 2.3</li>
    </ol>
    <li>(c.) Item 3</li>
    <li>(d.) Item 4</li>
</ol>

Browser output:

WeasyPrint output:

This also happens to showcase that nested ordered lists aren't handled correctly either. Changing type="a" to type="1" (default), creates the same output.

[MH-ZShearer]

I found out that passing --presentation-hints fixes the issue of ordered lists only using numbers. However, Item 3 and Item 4 end up being d. and e. respectively.

[liZe]

Hi!

ol and ul elements only allow li elements as children, embedding ol in ol is not valid HTML.

You can use this instead:

<ol type="a">
    <li>(a.) Item 1</li>
    <li>(b.) Item 2
      <ol type="1">
        <li>(1.) Item 2.1</li>
        <li>(2.) Item 2.2</li>
        <li>(3.) Item 2.3</li>
      </ol>
    </li>
    <li>(c.) Item 3</li>
    <li>(d.) Item 4</li>
</ol>

[MH-ZShearer]

Huh, I swore that is what I tried first. I suppose it was before I found out about --presentational-hints and it was an attempt to fix my ignorance.

Is there a reason that presentational hints aren't enabled by default? Reading the documentation left me with more questions than what it actually answered. Are there downsides to enabling it?

[liZe]

Huh, I swore that is what I tried first. I suppose it was before I found out about --presentational-hints and it was an attempt to fix my ignorance.

😀️

Is there a reason that presentational hints aren't enabled by default? Reading the documentation left me with more questions than what it actually answered. Are there downsides to enabling it?

The main reason is that it’s slow.

As most of these features are more or less deprecated in HTML, users generally prefer to use the corresponding CSS properties. For lists, for example, a lot of things can be handled using the CSS Lists and Counters module’s properties.

[MH-ZShearer]

That makes sense. Unfortunately, our use case is converting markdown files to PDFs with Pandoc and WeasyPrint. We had a specification in our contract that required a single ordered list to contain letters with a nested ordered list inside so using CSS to target such a specific thing (that was generic to all of our documentation) didn't feel right.

I expected that --presentation-hints was more the "true" representation of the webpage, however, I can definitely understand the performance impact of having it as the default.

Thank you for the assistance and information!