mdrefine

style/code-fence ​

Writes the fences of a fenced code block with one marker, and as long as its content allows: three characters, or one more than the longest line inside that holds only the marker, which would otherwise close the block. It also removes spaces and tabs between the opening fence and its info string.

Style rule, fixed by format. Presets: recommended (warn). Dialects: all. Options: marker.

Before:

markdown
~~~  sh
npm test
~~~

After:

markdown
```sh
npm test
```

marker is "```" (the default), "~~~", or "consistent", which takes the marker of the document's first fence.

Edge cases and advanced usage ​

Details: the info string's text and metadata, and the code content, stay as written; nested fences keep the outer fence long enough to contain them.

Left as written: indented code blocks, which have no fence, and a ~~~ fence whose info string contains a backtick, because a backtick fence cannot have one.

content/code-language reports a fence without a language; neither rule adds one.