# rehype-parse
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**[rehype][]** plugin to add support for parsing HTML input.
## Contents
* [What is this?](#what-is-this)
* [When should I use this?](#when-should-i-use-this)
* [Install](#install)
* [Use](#use)
* [API](#api)
* [`unified().use(rehypeParse[, options])`](#unifieduserehypeparse-options)
* [Examples](#examples)
* [Example: fragment versus document](#example-fragment-versus-document)
* [Example: whitespace around and inside ``](#example-whitespace-around-and-inside-html)
* [Example: parse errors](#example-parse-errors)
* [Syntax](#syntax)
* [Syntax tree](#syntax-tree)
* [Types](#types)
* [Compatibility](#compatibility)
* [Security](#security)
* [Contribute](#contribute)
* [Sponsor](#sponsor)
* [License](#license)
## What is this?
This package is a [unified][] ([rehype][]) plugin that defines how to take HTML
as input and turn it into a syntax tree.
When itβs used, HTML can be parsed and other rehype plugins can be used after
it.
See [the monorepo readme][rehype] for info on what the rehype ecosystem is.
## When should I use this?
This plugin adds support to unified for parsing HTML.
You can alternatively use [`rehype`][rehype-core] instead, which combines
unified, this plugin, and [`rehype-stringify`][rehype-stringify].
When youβre in a browser, trust your content, donβt need positional info, and
value a smaller bundle size, you can use [`rehype-dom-parse`][rehype-dom-parse]
instead.
This plugin is built on [`parse5`][parse5] and
[`hast-util-from-parse5`][hast-util-from-parse5], which deal with HTML-compliant
tokenizing, parsing, and creating nodes.
rehype focusses on making it easier to transform content by abstracting such
internals away.
## Install
This package is [ESM only][esm].
In Node.js (version 12.20+, 14.14+, or 16.0+), install with [npm][]:
```sh
npm install rehype-parse
```
In Deno with [Skypack][]:
```js
import rehypeParse from 'https://cdn.skypack.dev/rehype-parse@8?dts'
```
In browsers with [Skypack][]:
```html
```
## Use
Say we have the following module `example.js`:
```js
import {unified} from 'unified'
import rehypeParse from 'rehype-parse'
import rehypeRemark from 'rehype-remark'
import remarkStringify from 'remark-stringify'
main()
async function main() {
const file = await unified()
.use(rehypeParse)
.use(rehypeRemark)
.use(remarkStringify)
.process('Hello, world! ')
console.log(String(file))
}
```
β¦running that with `node example.js` yields:
```markdown
# Hello, world!
```
## API
This package exports no identifiers.
The default export is `rehypeParse`.
### `unified().use(rehypeParse[, options])`
Add support for parsing HTML input.
##### `options`
Configuration (optional).
###### `options.fragment`
Specify whether to parse as a fragment (`boolean`, default: `false`).
The default is to expect a whole document.
In document mode, unopened `html`, `head`, and `body` elements are opened.
###### `options.space`
Which space the document is in (`'svg'` or `'html'`, default: `'html'`).
When an `` element is found in the HTML space, `rehype-parse` already
automatically switches to and from the SVG space when entering and exiting it.
> π **Note**: rehype is not an XML parser.
> It supports SVG as embedded in HTML.
> It does not support the features available in XML.
> Passing SVG files might break but fragments of modern SVG should be fine.
> π **Note**: make sure to set `fragment: true` if `space: 'svg'`.
###### `options.emitParseErrors`
Emit [HTML parse errors][parse-errors] as warning messages
(`boolean`, default: `false`).
Specific rules can be turned off by setting their IDs in `options` to `false`
(or `0`).
The default, when `emitParseErrors: true`, is `true` (or `1`), and means that
rules emit as warnings.
Rules can also be configured with `2`, to turn them into fatal errors.
The list of parse errors:
* `abandonedHeadElementChild` β unexpected metadata element after head ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/abandoned-head-element-child/index.html))
* [`abruptClosingOfEmptyComment`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-abrupt-closing-of-empty-comment) β unexpected abruptly closed empty comment ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/abrupt-closing-of-empty-comment/index.html))
* [`abruptDoctypePublicIdentifier`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-abrupt-doctype-public-identifier) β unexpected abruptly closed public identifier ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/abrupt-doctype-public-identifier/index.html))
* [`abruptDoctypeSystemIdentifier`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-abrupt-doctype-system-identifier) β unexpected abruptly closed system identifier ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/abrupt-doctype-system-identifier/index.html))
* [`absenceOfDigitsInNumericCharacterReference`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-absence-of-digits-in-numeric-character-reference) β unexpected non-digit at start of numeric character reference ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/absence-of-digits-in-numeric-character-reference/index.html))
* [`cdataInHtmlContent`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-cdata-in-html-content) β unexpected CDATA section in HTML ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/cdata-in-html-content/index.html))
* [`characterReferenceOutsideUnicodeRange`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-character-reference-outside-unicode-range) β unexpected too big numeric character reference ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/character-reference-outside-unicode-range/index.html))
* `closingOfElementWithOpenChildElements` β unexpected closing tag with open child elements ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/closing-of-element-with-open-child-elements/index.html))
* [`controlCharacterInInputStream`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-control-character-in-input-stream) β unexpected control character ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/control-character-in-input-stream/index.html))
* [`controlCharacterReference`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-control-character-reference) β unexpected control character reference ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/control-character-reference/index.html))
* `disallowedContentInNoscriptInHead` β disallowed content inside `` in `` ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/disallowed-content-in-noscript-in-head/index.html))
* [`duplicateAttribute`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-duplicate-attribute) β unexpected duplicate attribute ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/duplicate-attribute/index.html))
* [`endTagWithAttributes`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-end-tag-with-attributes) β unexpected attribute on closing tag ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/end-tag-with-attributes/index.html))
* [`endTagWithTrailingSolidus`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-end-tag-with-trailing-solidus) β unexpected slash at end of closing tag ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/end-tag-with-trailing-solidus/index.html))
* `endTagWithoutMatchingOpenElement` β unexpected unopened end tag ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/end-tag-without-matching-open-element/index.html))
* [`eofBeforeTagName`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-eof-before-tag-name) β unexpected end of file ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/eof-before-tag-name/index.html))
* [`eofInCdata`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-eof-in-cdata) β unexpected end of file in CDATA ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/eof-in-cdata/index.html))
* [`eofInComment`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-eof-in-comment) β unexpected end of file in comment ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/eof-in-comment/index.html))
* [`eofInDoctype`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-eof-in-doctype) β unexpected end of file in doctype ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/eof-in-doctype/index.html))
* `eofInElementThatCanContainOnlyText` β unexpected end of file in element that can only contain text ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/eof-in-element-that-can-contain-only-text/index.html))
* [`eofInScriptHtmlCommentLikeText`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-eof-in-script-html-comment-like-text) β unexpected end of file in comment inside script ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/eof-in-script-html-comment-like-text/index.html))
* [`eofInTag`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-eof-in-tag) β unexpected end of file in tag ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/eof-in-tag/index.html))
* [`incorrectlyClosedComment`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-incorrectly-closed-comment) β incorrectly closed comment ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/incorrectly-closed-comment/index.html))
* [`incorrectlyOpenedComment`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-incorrectly-opened-comment) β incorrectly opened comment ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/incorrectly-opened-comment/index.html))
* [`invalidCharacterSequenceAfterDoctypeName`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-invalid-character-sequence-after-doctype-name) β invalid sequence after doctype name ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/invalid-character-sequence-after-doctype-name/index.html))
* [`invalidFirstCharacterOfTagName`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-invalid-first-character-of-tag-name) β invalid first character in tag name ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/invalid-first-character-of-tag-name/index.html))
* `misplacedDoctype` β misplaced doctype ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/misplaced-doctype/index.html))
* `misplacedStartTagForHeadElement` β misplaced `` start tag ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/misplaced-start-tag-for-head-element/index.html))
* [`missingAttributeValue`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-missing-attribute-value) β missing attribute value ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/missing-attribute-value/index.html))
* `missingDoctype` β missing doctype before other content ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/missing-doctype/index.html))
* [`missingDoctypeName`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-missing-doctype-name) β missing doctype name ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/missing-doctype-name/index.html))
* [`missingDoctypePublicIdentifier`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-missing-doctype-public-identifier) β missing public identifier in doctype ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/missing-doctype-public-identifier/index.html))
* [`missingDoctypeSystemIdentifier`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-missing-doctype-system-identifier) β missing system identifier in doctype ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/missing-doctype-system-identifier/index.html))
* [`missingEndTagName`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-missing-end-tag-name) β missing name in end tag ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/missing-end-tag-name/index.html))
* [`missingQuoteBeforeDoctypePublicIdentifier`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-missing-quote-before-doctype-public-identifier) β missing quote before public identifier in doctype ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/missing-quote-before-doctype-public-identifier/index.html))
* [`missingQuoteBeforeDoctypeSystemIdentifier`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-missing-quote-before-doctype-system-identifier) β missing quote before system identifier in doctype ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/missing-quote-before-doctype-system-identifier/index.html))
* [`missingSemicolonAfterCharacterReference`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-missing-semicolon-after-character-reference) β missing semicolon after character reference ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/missing-semicolon-after-character-reference/index.html))
* [`missingWhitespaceAfterDoctypePublicKeyword`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-missing-whitespace-after-doctype-public-keyword) β missing whitespace after public identifier in doctype ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/missing-whitespace-after-doctype-public-keyword/index.html))
* [`missingWhitespaceAfterDoctypeSystemKeyword`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-missing-whitespace-after-doctype-system-keyword) β missing whitespace after system identifier in doctype ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/missing-whitespace-after-doctype-system-keyword/index.html))
* [`missingWhitespaceBeforeDoctypeName`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-missing-whitespace-before-doctype-name) β missing whitespace before doctype name ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/missing-whitespace-before-doctype-name/index.html))
* [`missingWhitespaceBetweenAttributes`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-missing-whitespace-between-attributes) β missing whitespace between attributes ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/missing-whitespace-between-attributes/index.html))
* [`missingWhitespaceBetweenDoctypePublicAndSystemIdentifiers`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-missing-whitespace-between-doctype-public-and-system-identifiers) β missing whitespace between public and system identifiers in doctype ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/missing-whitespace-between-doctype-public-and-system-identifiers/index.html))
* [`nestedComment`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-nested-comment) β unexpected nested comment ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/nested-comment/index.html))
* `nestedNoscriptInHead` β unexpected nested `` in `` ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/nested-noscript-in-head/index.html))
* `nonConformingDoctype` β unexpected non-conforming doctype declaration ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/non-conforming-doctype/index.html))
* [`nonVoidHtmlElementStartTagWithTrailingSolidus`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-non-void-html-element-start-tag-with-trailing-solidus) β unexpected trailing slash on start tag of non-void element ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/non-void-html-element-start-tag-with-trailing-solidus/index.html))
* [`noncharacterCharacterReference`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-noncharacter-character-reference) β unexpected noncharacter code point referenced by character reference ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/noncharacter-character-reference/index.html))
* [`noncharacterInInputStream`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-noncharacter-in-input-stream) β unexpected noncharacter character ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/noncharacter-in-input-stream/index.html))
* [`nullCharacterReference`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-null-character-reference) β unexpected NULL character referenced by character reference ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/null-character-reference/index.html))
* `openElementsLeftAfterEof` β unexpected end of file ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/open-elements-left-after-eof/index.html))
* [`surrogateCharacterReference`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-surrogate-character-reference) β unexpected surrogate character referenced by character reference ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/surrogate-character-reference/index.html))
* [`surrogateInInputStream`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-surrogate-in-input-stream) β unexpected surrogate character
* [`unexpectedCharacterAfterDoctypeSystemIdentifier`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-unexpected-character-after-doctype-system-identifier) β invalid character after system identifier in doctype ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/unexpected-character-after-doctype-system-identifier/index.html))
* [`unexpectedCharacterInAttributeName`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-unexpected-character-in-attribute-name) β unexpected character in attribute name ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/unexpected-character-in-attribute-name/index.html))
* [`unexpectedCharacterInUnquotedAttributeValue`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-unexpected-character-in-unquoted-attribute-value) β unexpected character in unquoted attribute value ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/unexpected-character-in-unquoted-attribute-value/index.html))
* [`unexpectedEqualsSignBeforeAttributeName`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-unexpected-equals-sign-before-attribute-name) β unexpected equals sign before attribute name ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/unexpected-equals-sign-before-attribute-name/index.html))
* [`unexpectedNullCharacter`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-unexpected-null-character) β unexpected NULL character ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/unexpected-null-character/index.html))
* [`unexpectedQuestionMarkInsteadOfTagName`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-unexpected-question-mark-instead-of-tag-name) β unexpected question mark instead of tag name ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/unexpected-question-mark-instead-of-tag-name/index.html))
* [`unexpectedSolidusInTag`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-unexpected-solidus-in-tag) β unexpected slash in tag ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/unexpected-solidus-in-tag/index.html))
* [`unknownNamedCharacterReference`](https://html.spec.whatwg.org/multipage/parsing.html#parse-error-unknown-named-character-reference) β unexpected unknown named character reference ([example](https://github.com/rehypejs/rehype/blob/main/test/parse-error/unknown-named-character-reference/index.html))
###### `options.verbose`
Add extra positional info (`boolean`, default: `false`).
## Examples
### Example: fragment versus document
The following example shows the difference between parsing as a document and
parsing as a fragment:
```js
import {unified} from 'unified'
import rehypeParse from 'rehype-parse'
import rehypeStringify from 'rehype-stringify'
main()
async function main() {
const doc = 'Hi! Hello! '
console.log(
String(
await unified()
.use(rehypeParse, {fragment: true})
.use(rehypeStringify)
.process(doc)
)
)
console.log(
String(
await unified()
.use(rehypeParse, {fragment: false})
.use(rehypeStringify)
.process(doc)
)
)
}
```
β¦yields:
```html
Hi! Hello!
```
```html
Hi! Hello!
```
> π **Note**: observe that when a whole document is expected (second example),
> missing elements are opened and closed.
### Example: whitespace around and inside ``
The following example shows how whitespace is handled when around and directly
inside the `` element:
```js
import {unified} from 'unified'
import rehypeParse from 'rehype-parse'
import rehypeStringify from 'rehype-stringify'
main(`
Hi!
Hello!
`)
async function main(doc) {
console.log(
String(await unified().use(rehypeParse).use(rehypeStringify).process(doc))
)
}
```
β¦yields (where `β ` represents a space character):
```html
Hi!
Hello!
β β
```
> π **Note**: observe that the line ending before `` is ignored, the line
> ending and two spaces before `` is moved inside it, and the line ending
> after `` is moved before it.
This behavior is described by the HTML standard (see the section 13.2.6.4.1
βThe βinitialβ insertion modeβ and adjacent states) which rehype follows.
The changes to this meaningless whitespace should not matter, except when
formatting markup, in which case [`rehype-format`][rehype-format] can be used to
improve the source code.
### Example: parse errors
The following example shows how HTML parse errors can be enabled and configured:
```js
import {reporter} from 'vfile-reporter'
import {unified} from 'unified'
import rehypeParse from 'rehype-parse'
import rehypeStringify from 'rehype-stringify'
main()
async function main() {
const file = await unified()
.use(rehypeParse, {
emitParseErrors: true, // Emit all.
missingWhitespaceBeforeDoctypeName: 2, // Mark one as a fatal error.
nonVoidHtmlElementStartTagWithTrailingSolidus: false // Ignore one.
})
.use(rehypeStringify)
.process(`
Helloβ¦