Unexpected character `=` (U+003D) before name, expected a character that can start a name, such as a letter

mdx-bundler version: ^6.0.2
node version: 16.13.0
npm version: 8.1.0

Relevant code or config

import { bundleMDX } from 'mdx-bundler';

const mdxSource = `
---
title: Example Post
published: 2021-02-13
description: This is some description
---

# Wahoo

import Demo from './demo'

Here's a **neat** demo:

Adding a <= 10 to see if it breaks.

<Demo />
`.trim();

const run = async () => {
  const result = await bundleMDX(mdxSource, {
    files: {
      './demo.tsx': `
import * as React from 'react'

function Demo() {
  return <div>Neat demo!</div>
}

export default Demo
    `
    }
  });

  const { code, frontmatter } = result;
  console.log(code);
};

run();

What you did: The line Adding a <= 10 to see if it breaks. was added to the mdx file, rest of the content is similar to the demo provided in this repo readme. I have some mdx files which have statements like these (<=, >= etc). For all the files which have these characters, the mdx-bundler fails. I am using contentlayer which internally uses mdx-bundler and esbuild so this error was seen during that for which there is an open ticket seen here however this seems more like an bug in mdx-bundler and not contentlayer.

What happened: The build failed for such files which have these characters mentioned above. The screenshot is what seen in contentlayer

Error text seen while running the above mentioned code with mdx-bundler's bundleMDX function directly

> _mdx_bundler_entry_point-856386d9-f2ca-417c-b32b-7adff34d061b.mdx:13:10: error: [plugin: esbuild-xdm] Unexpected character `=` (U+003D) before name, expected a character that can start a name, such as a letter, `$`, or 
`_`
    13 │ Adding a <= 10 to see if it breaks
       ╵           ^

C:\Users\AkashRajpurohit\Documents\akash\akashrajpurohit.com\node_modules\esbuild\lib\main.js:1493
  let error = new Error(`${text}${summary}`);
              ^

Error: Build failed with 1 error:
_mdx_bundler_entry_point-856386d9-f2ca-417c-b32b-7adff34d061b.mdx:13:10: error: [plugin: esbuild-xdm] Unexpected character `=` (U+003D) before name, expected a character that can start a name, such as a letter, `$`, or `_`    at failureErrorWithLog (C:\Users\AkashRajpurohit\Documents\akash\akashrajpurohit.com\node_modules\esbuild\lib\main.js:1493:15)
    at C:\Users\AkashRajpurohit\Documents\akash\akashrajpurohit.com\node_modules\esbuild\lib\main.js:1151:28   
    at runOnEndCallbacks (C:\Users\AkashRajpurohit\Documents\akash\akashrajpurohit.com\node_modules\esbuild\lib\main.js:941:63)
    at buildResponseToResult (C:\Users\AkashRajpurohit\Documents\akash\akashrajpurohit.com\node_modules\esbuild\lib\main.js:1149:7)
    at C:\Users\AkashRajpurohit\Documents\akash\akashrajpurohit.com\node_modules\esbuild\lib\main.js:1258:14   
    at C:\Users\AkashRajpurohit\Documents\akash\akashrajpurohit.com\node_modules\esbuild\lib\main.js:629:9     
    at handleIncomingPacket (C:\Users\AkashRajpurohit\Documents\akash\akashrajpurohit.com\node_modules\esbuild\lib\main.js:726:9)
    at Socket.readFromStdout (C:\Users\AkashRajpurohit\Documents\akash\akashrajpurohit.com\node_modules\esbuild\lib\main.js:596:7)
    at Socket.emit (node:events:390:28)
    at addChunk (node:internal/streams/readable:315:12) {
  errors: [
    {
      detail: [13:11: Unexpected character `=` (U+003D) before name, expected a character that can start a name, such as a letter, `$`, or `_`] {
        reason: 'Unexpected character `=` (U+003D) before name, expected a character that can start a name, such as a letter, `$`, or `_`',
        line: 13,
        column: 11,
        source: 'micromark-extension-mdx-jsx',
        ruleId: 'unexpected-character',
        position: {
          start: {
            line: 13,
            column: 11,
            offset: 160,
            _index: 0,
            _bufferIndex: 10
          },
          end: { line: null, column: null }
        },
        fatal: true
      },
      location: {
        column: 10,
        file: '_mdx_bundler_entry_point-856386d9-f2ca-417c-b32b-7adff34d061b.mdx',
        length: 1,
        line: 13,
        lineText: 'Adding a <= 10 to see if it breaks',
        namespace: 'file',
        suggestion: ''
      },
      notes: [],
      pluginName: 'esbuild-xdm',
      text: 'Unexpected character `=` (U+003D) before name, expected a character that can start a name, such as a letter, `$`, or `_`'
    }
  ],
  warnings: []
}

kentcdodds / mdx-bundler

Unexpected character `=` (U+003D) before name, expected a character that can start a name, such as a letter #122