micromark-extension-mdx-expression

What is micromark-extension-mdx-expression?

The micromark-extension-mdx-expression npm package is designed to extend the micromark Markdown parser to support MDX expressions. This allows developers to embed JSX-like expressions within their Markdown content, which is particularly useful when using MDX to create interactive documentation or components within Markdown files.

What are micromark-extension-mdx-expression's main functionalities?

Parsing Inline Expressions

This feature allows the parsing of inline expressions embedded within curly braces. It is useful for inserting dynamic content directly into the text.

{`Hello, ${name}!`}

Parsing Block Expressions

This feature supports the use of block expressions, where more complex JavaScript logic can be embedded within Markdown, enabling the creation of dynamic and interactive content blocks.

{
  const name = 'World';
  return <div>Hello, {name}!</div>;
}

Other packages similar to micromark-extension-mdx-expression

remark-mdx

This package is similar to micromark-extension-mdx-expression as it also allows MDX capabilities in Markdown files. However, remark-mdx is built on top of the remark parser, which is a different Markdown parser compared to micromark used by micromark-extension-mdx-expression. This difference in underlying parsers can lead to variations in parsing behavior and plugin compatibility.

README

micromark-extension-mdx-expression

micromark extension to support MDX (or MDX.js) expressions.

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.

You should use this with mdast-util-mdx-expression (mdast). Alternatively, use either micromark-extension-mdx or micromark-extension-mdxjs with mdast-util-mdx to support all of MDX (or MDX.js). Or, use it through remark-mdx (remark).

Install

npm:

npm install micromark-extension-mdx-expression

Use

See mdast-util-mdx-expression for an example.

API

syntax(options?)

Support MDX (or MDX.js) expressions.

The export of syntax is a function that can be called with options and returns an extension for the micromark parser (to tokenize expressions; can be passed in extensions).

options

options.acorn

Acorn parser to use (Acorn, optional).

options.acornOptions

Options to pass to acorn (Object, default: {ecmaVersion: 2020, sourceType: 'module'}). All fields can be set. Positional info (loc, range) is set on ES nodes regardless of acorn options.

options.addResult

Whether to add an estree field to mdxFlowExpression and mdxTextExpression tokens with the results from acorn (boolean, default: false). Note that expressions can be empty or be just comments, in which case estree will be undefined.

Syntax

This extensions support both MDX and MDX.js. The first is agnostic to the programming language (it could contain Rust or so), the last is specific to JavaScript. To turn on gnostic mode, pass acorn.

There are two types of expressions: in text (inline, span) or in flow (block). They start with {.

Depending on whether acorn is passed, expressions are either parsed in several tries until whole JavaScript is found (as in, nested curly braces depend on JS expression nesting), or they are counted and must be balanced.

Expressions end with }.

For flow (block) expressions, optionally markdown spaces ( or \t) can occur after the closing brace, and finally a markdown line ending (\r, \n) or the end of the file must follow.

While markdown typically knows no errors, for MDX it is decided to instead throw on invalid syntax.

Here is an expression in a heading:

## Hello, {1 + 1}!

In agnostic mode, balanced braces can occur: {a + {b} + c}.

In gnostic mode, the value of the expression must be JavaScript, so
this would fail: {!}.
But, in gnostic mode, braces can be in comments, strings, or in other
places: {1 /* { */ + 2}.

The previous examples were text (inline, span) expressions, they can
also be flow (block):

{
  1 + 1
}

This is incorrect, because there are further characters:

{
  1 + 1
}!

Blank lines cannot occur in text, because markdown has already split them in
separate constructs, so this is incorrect: {1 +

1}


In flow, you can have blank lines:

{
  1 +

  2
}

Errors

Unexpected end of file in expression, expected a corresponding closing brace for {

This error occurs if a { was seen without a } (source: micromark-extension-mdx-expression, rule id: unexpected-eof). For example:

a { b

Could not parse expression with acorn: Unexpected content after expression

This error occurs when there is more content after a JS expression (source: micromark-extension-mdx-expression, rule id: acorn). For example:

a {"b" "c"} d

Could not parse expression with acorn: $error

This error occurs if acorn crashes (source: micromark-extension-mdx-expression, rule id: acorn). For example:

a {var b = "c"} d

Tokens

Two tokens are used, mdxFlowExpression and mdxTextExpression, to reflect flow and text expressions.

They include:

• lineEnding for the markdown line endings \r, \n, and \r\n
• mdxFlowExpressionMarker and mdxTextExpressionMarker for the braces
• whitespace for markdown spaces and tabs in blank lines
• mdxFlowExpressionChunk and mdxTextExpressionChunk for chunks of expression content

Related

• micromark/micromark — the smallest commonmark-compliant markdown parser that exists
• micromark/micromark-extension-mdx — micromark extension to support MDX
• micromark/micromark-extension-mdxjs — micromark extension to support MDX.js
• micromark/micromark-extension-mdx-jsx — micromark extension to support MDX (or MDX.js) JSX
• micromark/micromark-extension-mdx-md — micromark extension to support misc MDX changes
• micromark/micromark-extension-mdxjs-esm — micromark extension to support MDX.js import/exports
• syntax-tree/mdast-util-mdx — mdast utility to support MDX (or MDX.js)

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.

License

MIT © Titus Wormer