control character and puntuation cause extra emphasis to appear

[ChristianMurphy]

Initial checklist

• I read the support docs
• I read the contributing guide
• I agree to follow the code of conduct
• I searched issues and couldn’t find anything (or linked relevant results below)

Affected packages and versions

3.0.5

Link to runnable example

https://stackblitz.com/edit/node-njevp4?file=index.js

Steps to reproduce

import { micromark } from 'micromark';
import { Parser, HtmlRenderer } from 'commonmark';
import rehypeParse from 'rehype-parse';
import { unified } from 'unified';
import { visit } from 'unist-util-visit';
import lodash from 'lodash';

const reader = new Parser();
const writer = new HtmlRenderer();
function scrubber(tree) {
  visit(tree, function (node) {
    node.data = undefined;
    node.value = undefined;
    node.position = undefined;
  });

  return tree;
}

const commonmark = (buf) => writer.render(reader.parse(buf));

const content = `example*�.*example example**`;

const micromarkHtml = micromark(content, {
  allowDangerousHtml: true,
  allowDangerousProtocol: true,
}).trim();
const commonmarkHtml = commonmark(content).trim();

const micromarkHtmlAst = scrubber(
  unified().use(rehypeParse, { fragment: true }).parse(micromarkHtml)
);
const commonmarkHtmlAst = scrubber(
  unified().use(rehypeParse, { fragment: true }).parse(commonmarkHtml)
);

console.log('micromark');
console.log(micromarkHtml);
console.log('');
console.log(JSON.stringify(micromarkHtmlAst, null, 4));
console.log('');
console.log('commonmark');
console.log(commonmark(content));
console.log('');
console.log(JSON.stringify(commonmarkHtmlAst, null, 2));
console.log(lodash.isEqual(micromarkHtmlAst, commonmarkHtmlAst));

Expected behavior

single emphasis in the document

<p>example*�.<em>example example</em>*</p>

with the HTML structure

{
  "type": "root",
  "children": [
    {
      "type": "element",
      "tagName": "p",
      "properties": {},
      "children": [
        {
          "type": "text"
        },
        {
          "type": "element",
          "tagName": "em",
          "properties": {},
          "children": [
            {
              "type": "text"
            }
          ]
        },
        {
          "type": "text"
        }
      ]
    }
  ]
}

Actual behavior

extra emphasis is added

<p>example<em>�.<em>example example</em></em></p>

changing the structure

{
    "type": "root",
    "children": [
        {
            "type": "element",
            "tagName": "p",
            "properties": {},
            "children": [
                {
                    "type": "text"
                },
                {
                    "type": "element",
                    "tagName": "em",
                    "properties": {},
                    "children": [
                        {
                            "type": "text"
                        },
                        {
                            "type": "element",
                            "tagName": "em",
                            "properties": {},
                            "children": [
                                {
                                    "type": "text"
                                }
                            ]
                        }
                    ]
                }
            ]
        }
    ]
}

Runtime

Node v16

Package manager

npm v7

OS

Linux

Build and bundle tools

No response

[ChristianMurphy]

other example with same issue

example*�+*example example**

example*�.*example example**

[ChristianMurphy]

possibly related to syntax-tree/mdast-util-from-markdown#15

[ChristianMurphy]

Also potentially related to #91 (comment)