micromark-extension-mdx-jsx
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!Chatchat-badgechatmicromark extension to support MDXmdxjs JSX (
<Component />
).Contents
* [`mdxJsx(options?)`](#mdxjsxoptions)
* [`Options`](#options)
* [Unexpected end of file $at, expected $expect](#unexpected-end-of-file-at-expected-expect)
* [Unexpected character $at, expected $expect](#unexpected-character-at-expected-expect)
* [Unexpected lazy line in container, expected line to be…](#unexpected-lazy-line-in-container-expected-line-to-be)
What is this?
This package contains an extension that adds support for the JSX syntax enabled by MDXmdxjs tomicromark
micromark.
These extensions are used inside MDX.
It mostly matches how JSX works in most places that support it (TypeScript,
Babel, esbuild, SWC, etc).This package can be made aware or unaware of JavaScript syntax. When unaware, expressions could include Rust or variables or whatnot.
When to use this
This project is useful when you want to support JSX in markdown.You can use this extension when you are working with
micromark
micromark.
To support all MDX features, use
micromark-extension-mdxjs
micromark-extension-mdxjs instead.When you need a syntax tree, combine this package with
mdast-util-mdx-jsx
mdast-util-mdx-jsx.All these packages are used in
remark-mdx
remark-mdx, which focusses on
making it easier to transform content by abstracting these internals away.When you are using
mdx-js/mdx
mdxjs, all of this is already included.Install
This package is ESM onlyesm. In Node.js (version 16+), install with npm:npm install micromark-extension-mdx-jsx
In Deno with
esm.sh
esmsh:import {mdxJsx} from 'https://esm.sh/micromark-extension-mdx-jsx@2'
In browsers with
esm.sh
esmsh:<script type="module">
import {mdxJsx} from 'https://esm.sh/micromark-extension-mdx-jsx@2?bundle'
</script>
Use
import {micromark} from 'micromark'
import {mdxJsx} from 'micromark-extension-mdx-jsx'
const output = micromark('a <b c d="e" /> f', {extensions: [mdxJsx()]})
console.log(output)
Yields:
<p>a f</p>
…which is useless: go to a syntax tree with
mdast-util-from-markdown
mdast-util-from-markdown and
mdast-util-mdx-jsx
mdast-util-mdx-jsx instead.API
This package exports the identifiermdxJsx
api-mdx-jsx.
There is no default export.The export map supports the
development
conditiondevelopment.
Run node --conditions development module.js
to get instrumented dev code.
Without this condition, production code is loaded.mdxJsx(options?)
Create an extension for micromark
to enable MDX JSX syntax.Parameters
options
(Options
api-options, optional)
— configuration
Returns
Extension formicromark
that can be passed in extensions
to enable MDX
JSX syntax (Extension
micromark-extension).Options
Configuration (TypeScript type).Fields
— acorn parser to use
acornOptions
(AcornOptions
acorn-options, default:
`{ecmaVersion: 2024, locations: true, sourceType: 'module'}`)
— configuration for acorn; all fields except `locations` can be set
addResult
(boolean
, default:false
)
— whether to add `estree` fields to tokens with results from acorn
Authoring
When authoring markdown with JSX, keep in mind that MDX is a whitespace sensitive and line-based language, while JavaScript is insensitive to whitespace. This affects how markdown and JSX interleave with eachother in MDX. For more info on how it works, see § Interleavingmdxjs-interleaving on the MDX site.Comments inside tags
JavaScript comments in JSX are not supported.Incorrect:
```mdx-invalid comment!//>
Correct:
```mdx
<hi/>
<hello
/>
A PR that adds support for them would be accepted.
Element or fragment attribute values
JSX elements or JSX fragments as attribute values are not supported. The reason for this change is that it would be confusing whether markdown would work.Incorrect:
```mdx-invalid Venus</> /> Pluto />
Correct:
```mdx
<welcome name='Mars' />
<welcome name={<span>Jupiter</span>} />
Greater than (>
) and right curly brace (}
)
JSX does not allow U+003E GREATER THAN (>
) or U+007D RIGHT CURLY BRACE
(}
) literally in text, they need to be encoded as character references
(or expressions).
There is no good reason for this (some JSX parsers agree with us and don’t
crash either).
Therefore, in MDX, U+003E GREATER THAN (>
) and U+007D RIGHT CURLY BRACE
(}
) are fine literally and don’t need to be encoded.Syntax
JSX forms with the following BNF:mdxjsxflow ::= mdxjsx spaceortab mdxjsx spaceortab
mdxjsxtext ::= mdxjsx
; constraint: markdown whitespace (<a href=#x-space-or-tab>space_or_tab</a> | <a href=#x-eol>eol</a>
) is NOT
; allowed directly after <
in order to allow 1 < 3
in markdown.
mdxjsx ::=
'<' closing
whitespace name attributesafteridentifier closing
whitespace '>'
attributesafteridentifier ::=
1whitespace (attributesboolean | attributesvalue) |
whitespace attributesexpression |
attributesaftervalue ::=
whitespace (attributesboolean | attributesexpression | attributesvalue)
attributesboolean ::= key attributesafteridentifier
; Note: in gnostic mode the value of the expression must instead be a single valid ES spread
; expression
attributesexpression ::= expression attributesaftervalue
attributesvalue ::= key initializer attributesaftervalue
closing ::= whitespace '/'
name ::= identifier local | members
key ::= identifier local
local ::= whitespace ':' whitespace identifier
members ::= member member
member ::= whitespace '.' whitespace identifier
identifier ::= identifierstart identifierpart
initializer ::= whitespace '=' whitespace value
value ::= doublequoted | singlequoted | expression
; Note: in gnostic mode the value must instead be a single valid ES expression
expression ::= '{' (expressiontext | expression) '}'
doublequoted ::= '"' doublequotedtext '"'
singlequoted ::= "'" singlequotedtext "'"
whitespace ::= eswhitespace
doublequotedtext ::= char - '"'
singlequotedtext ::= char - "'"
expressiontext ::= char - '{' - '}'
identifierstart ::= esidentifierstart
identifierpart ::= esidentifierpart | '-'
spaceortab ::= '\t' | ' '
eol ::= '\n' | '\r' | '\r\n'
; ECMAScript
; See “IdentifierStart”: <https://tc39.es/ecma262/#prod-IdentifierStart>
esidentifierstart ::= ?
; See “IdentifierPart”: <https://tc39.es/ecma262/#prod-IdentifierPart>
esidentifierpart ::= ?
; See “Whitespace”: <https://tc39.es/ecma262/#prod-WhiteSpace>
eswhitespace ::= ?
As the flow construct occurs in flow, like all flow constructs, it must be followed by an eol (line ending) or eof (end of file).
The grammar for JSX in markdown is much stricter than that of HTML in markdown. The primary benefit of this is that tags are parsed into tokens, and thus can be processed. Another, arguable, benefit of this is that it comes with syntax errors: if an author types something that is nonsensical, an error is thrown with information about where it happened, what occurred, and what was expected instead.
This extension supports expressions both aware and unaware to JavaScript (respectively gnostic and agnostic). Depending on whether acorn is passed, either valid JavaScript must be used in expressions, or arbitrary text (such as Rust code or so) can be used.
More on this can be found in § Syntax of
micromark-extension-mdx-expression
expression-syntax.Errors
In aware (gnostic) mode, expressions are parsed withmicromark-extension-mdx-expression
micromark-extension-mdx-expression,
which throws some more errors.Unexpected end of file $at, expected $expect
This error occurs for many different reasons if something was opened but not closed (source:micromark-extension-mdx-jsx
, rule id: unexpected-eof
).Some examples are:
```mdx-invalid <
### Unexpected character $at, expected $expect
This error occurs for many different reasons if an unexpected character is seen
(source: `micromark-extension-mdx-jsx`, rule id: `unexpected-character`).
Some examples are:
```mdx-invalid
<.>
</.>
<a?>
<a:+>
<a./>
<a b!>
<a b:1>
<a b=>
<a/->
Unexpected lazy line in container, expected line to be…
This error occurs if a<
was seen in a container which then has lazy content
(source: micromark-extension-mdx-jsx
, rule id: unexpected-lazy
).
For example:```mdx-invalid
b> ```Tokens
Many tokens are used:
mdxJsxFlowTag
for the whole JSX tag (<a>
)mdxJsxTextTag
^mdxJsxFlowTagMarker
for the tag markers (<
,>
)mdxJsxTextTagMarker
^mdxJsxFlowTagClosingMarker
for the/
marking a closing tag (</a>
)mdxJsxTextTagClosingMarker
^mdxJsxFlowTagSelfClosingMarker
for the/
marking a self-closing tag(`<a/>`)
mdxJsxTextTagSelfClosingMarker
^mdxJsxFlowTagName
for the whole tag name (a:b
in<a:b>
)mdxJsxTextTagName
^mdxJsxFlowTagNamePrimary
for the first name (a
in<a:b>
)mdxJsxTextTagNamePrimary
^mdxJsxFlowTagNameMemberMarker
for the.
marking in members (<a.b>
)mdxJsxTextTagNameMemberMarker
^mdxJsxFlowTagNameMember
for member names (b
in<a:b>
)mdxJsxTextTagNameMember
^mdxJsxFlowTagNamePrefixMarker
for the:
between primary and local(`<a:b>`)
mdxJsxTextTagNamePrefixMarker
^mdxJsxFlowTagNameLocal
for the local name (b
in<a:b>
)mdxJsxTextTagNameLocal
^mdxJsxFlowTagExpressionAttribute
for whole expression attributes(`<a {...b}>`)
mdxJsxTextTagExpressionAttribute
^mdxJsxFlowTagExpressionAttributeMarker
for{
,}
in expressionattributes
mdxJsxTextTagExpressionAttributeMarker
^mdxJsxFlowTagExpressionAttributeValue
for chunks of what’s insideexpression attributes
mdxJsxTextTagExpressionAttributeValue
^mdxJsxFlowTagAttribute
for a whole normal attribute (<a b>
)mdxJsxTextTagAttribute
^mdxJsxFlowTagAttributeName
for the whole name of an attribute (b:c
in`<a b:c>`)
mdxJsxTextTagAttributeName
^mdxJsxFlowTagAttributeNamePrimary
for the first name of an attribute (b
in `<a b:c>`)
mdxJsxTextTagAttributeNamePrimary
^mdxJsxFlowTagAttributeNamePrefixMarker
for the:
between primary andlocal (`<a b:c>`)
mdxJsxTextTagAttributeNamePrefixMarker
^mdxJsxFlowTagAttributeNameLocal
for the local name of an attribute (c
in `<a b:c>`)
mdxJsxTextTagAttributeNameLocal
^mdxJsxFlowTagAttributeInitializerMarker
for the=
between an attributename and value
mdxJsxTextTagAttributeInitializerMarker
^mdxJsxFlowTagAttributeValueLiteral
for a string attribute value(`<a b="">`)
mdxJsxTextTagAttributeValueLiteral
^mdxJsxFlowTagAttributeValueLiteralMarker
for the quotes around a stringattribute value (`"` or `'`)
mdxJsxTextTagAttributeValueLiteralMarker
^mdxJsxFlowTagAttributeValueLiteralValue
for chunks of what’s insidestring attribute values
mdxJsxTextTagAttributeValueLiteralValue
^mdxJsxFlowTagAttributeValueExpression
for an expression attribute value(`<a b={1}>`)
mdxJsxTextTagAttributeValueExpression
^mdxJsxFlowTagAttributeValueExpressionMarker
for the{
and}
ofexpression attribute values
mdxJsxTextTagAttributeValueExpressionMarker
^mdxJsxFlowTagAttributeValueExpressionValue
for chunks of what’s insideexpression attribute values
mdxJsxTextTagAttributeValueExpressionValue
^Types
This package is fully typed with TypeScript. It exports the additional typeOptions
api-options.Compatibility
Projects maintained by the unified collective are compatible with maintained versions of Node.js.
When we cut a new major release, we drop support for unmaintained versions of Node. This means we try to keep the current release line,micromark-extension-mdx-jsx@^2
, compatible with Node.js 16.
This package works withmicromark
version3
and later.Security
This package is safe.Related
— support all MDX syntax
— support MDX JSX in mdast
— support all MDX syntax in remark
Contribute
Seecontributing.md
inmicromark/.github
contributing for ways to get started. Seesupport.md
support for ways to get help.
This project has a code of conductcoc. By interacting with this repository, organization, or community you agree to abide by its terms.License
MITlicense © Titus Wormerauthor