How should I get backtick count of fenced code block?

[yumetodo]

According to the CommonMark spec, fenced code block can be nested like below:

`````markdown
````markdown
```typescript
console.log("arikitari na sekai");
```
````
`````

To build markdown from pulldown-cmark's event system like pulldown-cmark-to-cmark, backtick count information is required(In the above example, backtick count is 5). Without the information, we have no choice but to use the hard-coded value.

However, currently, the Fenced event doesn't provide the information.
https://docs.rs/pulldown-cmark/0.7.2/pulldown_cmark/enum.CodeBlockKind.html#variant.Fenced

$cat sample.md
`````markdown
````markdown
```typescript
console.log("arikitari na sekai");
```
````
`````

$cat sample.md | pulldown-cmark -e
0..90: Start(CodeBlock(Fenced(Borrowed("markdown"))))
14..85: Text(Borrowed("````markdown\n```typescript\nconsole.log(\"arikitari na sekai\");\n```\n````\n"))
0..90: End(CodeBlock(Fenced(Borrowed("markdown"))))
EOF

How should I get it?

ref:

• Is it possible to write back code block backtick count to original? Byron/pulldown-cmark-to-cmark#20
• コードブロックを正確に書き戻せていない問題 yumetodo/markdown_img_url_editor#40

[marcusklaas]

Hi. Apologies for the delay in responding to this.

You may have figured this out yourself by now, but if you haven't, this may be one way to do it: take the starting byte of the fenced code block and use that as an index into the source text. You can then slice the text starting from that byte and count the number of backticks.

if let (Event::Start(Tag::CodeBlock(CodeBlockKind::Fenced(..))), range) = event {
    let num_backticks = source_text[range].chars().take_while(|c| c == '`').count();
}

Hope this works for you!