The Markdown widget isn't handling ordered lists correctly

[davep]

In Markdown the number prefix for an item in an ordered list normally isn't important. Every item can start with any valid numeric value; rendering will have them as an ordered sequence of numbers starting with the number of the first item.

For example:

1. One
1. Two
1. Three
1. Four
1. Five

comes out as:

1. One
2. Two
3. Three
4. Four
5. Five

However, in our Markdown widget at the moment, it appears like this:

This may be down to the underlying markdown parser we're using. It says it conforms to the CommonMark specification, and that specification does state:

The start number of an ordered list is determined by the list number of its initial list item. The numbers of subsequent list items are disregarded.
-- Section 5.3 of v0.30

so either we need to do something at our end to do that or enable that, or we may need to raise an issue upstream.

[davep]

Trying the live demo it looks like that does the right thing; which would suggest that the handling of this might need to be done in the code that uses the library (I'm not saying that for certain; just that on the surface it suggests that).

[TomJGooding]

Rendering html as shown in the live demo would only involve creating the appropriate <ol> and <li> tags wouldn't it, rather than any actual numbering logic?

According to the docs for token.info, this is "The string value of the item marker for ordered-list “list_item_open” tokens".

So possibly the code here is actually just using the number from the original?

        ...
        for token in parser.parse(markdown):
            ...
            elif token.type == "list_item_open":
                if token.info:
                    stack.append(MarkdownOrderedListItem(f"{token.info}. "))

[davep]

Yup, I think we'll need to pull out the initial value and do some increment of our own.

[TomJGooding]

I suppose an alternative if you wanted to avoid adding your own code to handle this would be to run the markdown through a formatter before trying to parse it?

I haven't read the docs in much detail yet but something like...

import mdformat

unformatted = """
1. One
1. Two
1. Three
1. Four
1. Five
"""

formatted = mdformat.text(
    unformatted,
    options={
        "number": True,  # switch on consecutive numbering of ordered lists
    },
)

print(formatted)
# 1. One
# 2. Two
# 3. Three
# 4. Four
# 5. Five

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