README
micromark-extension-mdxjs-esm
micromark extension to support MDX.js ESM import/exports.
This package provides the low-level modules for integrating with the micromark tokenizer but has no handling of compiling to HTML: go to a syntax tree instead.
When to use this
This package is already included in xdm and mdx-js/mdx
(next).
You should probably use micromark-extension-mdx
or
micromark-extension-mdxjs
instead, which combine this package with
other MDX features.
Alternatively, if you’re using micromark
or
mdast-util-from-markdown
and you don’t want all of MDX, use
this package.
Install
This package is ESM only:
Node 12+ is needed to use it and it must be import
ed instead of require
d.
npm:
npm install micromark-extension-mdxjs-esm
Use
import * as acorn from 'acorn'
import {micromark} from 'micromark'
import {mdxjsEsm} from 'micromark-extension-mdxjs-esm'
const output = micromark('import a from "b"\n\n# c', {
extensions: [mdxjsEsm({acorn})]
})
console.log(output)
Yields:
<h1>c</h1>
…which is rather useless: go to a syntax tree with
mdast-util-from-markdown
and
mdast-util-mdx-expression
instead.
API
This package exports the following identifiers: mdxjsEsm
.
There is no default export.
The export map supports the endorsed
development
condition.
Run node --conditions development module.js
to get instrumented dev code.
Without this condition, production code is loaded.
mdxjsEsm(options)
A function that can be called with options that returns an extension for
micromark to parse ESM (can be passed in extensions
).
options
options.acorn
Acorn parser to use (Acorn
, required).
options.acornOptions
Options to pass to acorn (Object
, default: {ecmaVersion: 2020, locations: true, sourceType: 'module'}
).
All fields except for locations
can be set.
options.addResult
Whether to add an estree
field to mdxjsEsm
tokens with results from acorn
(boolean
, default: false
).
Syntax
All valid imports and exports are supported, depending on what the given acorn instance and configuration supports.
When the lowercase strings export
or import
are found, followed by unicode
whitespace (\s
), we expect JavaScript.
Otherwise, like normal in markdown, we exit and it’ll end up as a paragraph.
We continue parsing until we find a line ending followed by a blank line.
At that point, we parse with acorn: it if parses, we found our block.
Otherwise, if parsing failed at the last character, we assume it’s a blank line
in code: we continue on until the next blank line and try again.
Otherwise, the acorn error is thrown.
import a from "b"
import * as a from "b"
import {a} from "b"
import {a as b} from "c"
import a, {b as c} from "d"
import a, * as b from "c"
import "a"
export var a = ""
export const a = ""
export let a = ""
export var a, b
export var a = "a", b = "b"
export function a() {}
export class a {}
export var {a} = {}
export var {a: b} = {}
export var [a] = []
export default a = 1
export default function a() {}
export default class a {}
export * from "a"
export * as a from "b"
export {a} from "b"
export {a as b} from "c"
export {default} from "b"
export {default as a, b} from "c"
{/* Blank lines are supported in expressions: */}
export function a() {
return "b"
}
{/* A blank line must be used after import/exports: this is incorrect! */}
import a from "b"
## Hello, world!
Errors
Could not parse import/exports with acorn: $error
This error occurs if acorn crashes (source: micromark-extension-mdxjs-esm
,
rule id: acorn
).
For example:
import 1/1
$type
in code: only import/exports are supported
Unexpected This error occurs when a non-ESM construct is found (source:
micromark-extension-mdxjs-esm
, rule id: non-esm
).
For example:
export var a = 1
var b
Tokens
An mdxjsEsm
token is used to reflect the block of import/exports in markdown.
It includes:
lineEnding
for the\r
,\n
, and\r\n
lineEndingBlank
for the same characters but when after potential whitespace and another line endingwhitespace
for markdown spaces and tabs in blank linesmdxjsEsmData
for any character in a line ofmdxjsEsm
Related
micromark/micromark
— the smallest commonmark-compliant markdown parser that existsmicromark/micromark-extension-mdx
— support MDXmicromark/micromark-extension-mdxjs
— support MDX.jsmicromark/micromark-extension-mdx-expression
— support MDX (or MDX.js) expressionsmicromark/micromark-extension-mdx-jsx
— support MDX (or MDX.js) JSXmicromark/micromark-extension-mdx-md
— support misc MDX changessyntax-tree/mdast-util-mdx
— support MDX (or MDX.js) in mdast
Contribute
See contributing.md
in micromark/.github
for ways to get
started.
See support.md
for ways to get help.
This project has a code of conduct. By interacting with this repository, organization, or community you agree to abide by its terms.