[Bug] (MarkdownViewer Control) Markdown content cannot have 0 as starting index for numbered lists

[chaojian-zhang]

The Markdown property of MarkdownViewer control seem not able to have 0 in a numbered list. An ArgumentException will be thrown saying 0 is not a valid StartIndex.

I am not sure whether this is related to MarkdownPipelineBuilder or I need to enable some UseSupportedExtensions()?

VS Setup: MarkdigWPFNumberList.zip

[Kryptos-FR]

As far as the commonmark specification goes, ordered list must start with 1.

Source: https://spec.commonmark.org/0.29/#ordered-list-marker

[chaojian-zhang]

I checked the spec and think the line "An ordered list marker is a sequence of 1–9 arabic digits (0-9), followed by either a . character or a ) character." clearly allows it.

Also see this discussion.

Thanks.

[Kryptos-FR]

I guess you misunderstand the spec. It clearly states that it must start with 1. That's what sequence 1-9 means. And later in the paragraph it is even more explicit: the start number must be 1.

In any case, markdig.wpf relies on what the markdig library parses. So if you think it is a bug, you should open an issue there.

But as can be seen in the babelmark benchmark, all commonmark-complying implementations don't support 0 as a starting index.

Final note, this exception happens in WPF (PresentationFramework) implementation of List (in namespace System.Windows.Documents), so there is nothing I can do about it unfortunately:

• https://docs.microsoft.com/en-us/dotnet/api/system.windows.documents.list.startindex?view=netframework-4.8#System_Windows_Documents_List_StartIndex)
• https://referencesource.microsoft.com/#PresentationFramework/src/Framework/System/Windows/Documents/List.cs