# rehype-parse
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[Parser][] for **[unified][]**.
Parses HTML to **[hast][]** syntax trees.
Used in the [**rehype** processor][processor] but can be used on its own as
well.
* * *
**Announcing the unified collective! π
[Read more about it on Medium Β»][announcement]**
## Sponsors
## Installation
[npm][]:
```bash
npm install rehype-parse
```
## Usage
This example shows how we parse HTML with this module and configure it to emit
parse errors except for duplicate attributes.
Then we transform HTML to markdown with [`rehype-remark`][rehype-remark] and
finally compile that markdown with [`remark-stringify`][remark-stringify].
Say we have the following file, `example.html`, with a few errors:
```html
Helloβ¦
World!
```
And our script, `example.js`, looks as follows:
```js
var vfile = require('to-vfile')
var report = require('vfile-reporter')
var unified = require('unified')
var parse = require('rehype-parse')
var rehype2remark = require('rehype-remark')
var stringify = require('remark-stringify')
unified()
.use(parse, {emitParseErrors: true, duplicateAttribute: false})
.use(rehype2remark)
.use(stringify)
.process(vfile.readSync('example.html'), function(err, file) {
console.error(report(err || file))
console.log(String(file))
})
```
Now, running `node example` yields:
```txt
example.html
1:10-1:10 warning Missing whitespace before doctype name missing-whitespace-before-doctype-name parse-error
3:1-3:6 warning Unexpected trailing slash on start tag of non-void element non-void-html-element-start-tag-with-trailing-solidus parse-error
β 2 warnings
```
```markdown
# World!
```
## API
### `processor.use(parse[, options])`
Configure the `processor` to read HTML as input and process a
**[hast][]** syntax tree.
##### `options`
###### `options.fragment`
Specify whether to parse a fragment (`boolean`, default: `false`),
instead of a complete document. In document mode, unopened `html`,
`head`, and `body` elements are opened in just the right places.
###### `options.space`
> β οΈ rehype is not an XML parser. It support SVG as embedded in HTML, but not
> the features available in the rest of XML/SVG. Passing SVG files could strip
> useful information, but fragments of modern SVG should be fine.
Whether the document is in the `'html'` or `'svg'` space (`'svg'` or `'html'`,
default: `'html'`).
If an `svg` element is found in the HTML space, `toHTML` automatically switches
to the SVG space when entering the element, and switches back when leaving.
**Note**: make sure to set `fragment: true` if `space: 'svg'`.
###### `options.emitParseErrors`
> β οΈ Parse errors are currently being added to HTML.
> Not all errors emitted by parse5 (or rehype-parse) are specced yet.
> Some documentation may still be missing.
Emit parse errors while parsing on the [vfile][] (`boolean`, default: `false`).
Setting this to true starts emitting [HTML parse errors][parse-errors].
Specific rules can be turned off by setting them 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 specific parse errors that are currently supported are detailed below:
* `abandonedHeadElementChild` β unexpected metadata element after head ([example](https://github.com/rehypejs/rehype/blob/master/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/master/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/master/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/master/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/master/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/master/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/master/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/master/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/master/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/master/test/parse-error/control-character-reference/index.html))
* `disallowedContentInNoscriptInHead` β disallowed content inside \`<noscript>\` in \`<head>\` ([example](https://github.com/rehypejs/rehype/blob/master/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/master/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/master/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/master/test/parse-error/end-tag-with-trailing-solidus/index.html))
* `endTagWithoutMatchingOpenElement` β unexpected unopened end tag ([example](https://github.com/rehypejs/rehype/blob/master/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/master/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/master/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/master/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/master/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/master/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/master/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/master/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/master/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/master/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/master/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/master/test/parse-error/invalid-first-character-of-tag-name/index.html))
* `misplacedDoctype` β misplaced doctype ([example](https://github.com/rehypejs/rehype/blob/master/test/parse-error/misplaced-doctype/index.html))
* `misplacedStartTagForHeadElement` β misplaced \`<head>\` start tag ([example](https://github.com/rehypejs/rehype/blob/master/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/master/test/parse-error/missing-attribute-value/index.html))
* `missingDoctype` β missing doctype before other content ([example](https://github.com/rehypejs/rehype/blob/master/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/master/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/master/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/master/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/master/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/master/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/master/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/master/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/master/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/master/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/master/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/master/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/master/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/master/test/parse-error/nested-comment/index.html))
* `nestedNoscriptInHead` β unexpected nested \`<noscript>\` in \`<head>\` ([example](https://github.com/rehypejs/rehype/blob/master/test/parse-error/nested-noscript-in-head/index.html))
* `nonConformingDoctype` β unexpected non-conforming doctype declaration ([example](https://github.com/rehypejs/rehype/blob/master/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/master/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/master/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/master/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/master/test/parse-error/null-character-reference/index.html))
* `openElementsLeftAfterEof` β unexpected end of file ([example](https://github.com/rehypejs/rehype/blob/master/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/master/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/master/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/master/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/master/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/master/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/master/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/master/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/master/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/master/test/parse-error/unknown-named-character-reference/index.html))
###### `options.verbose`
Patch extra positional information (`boolean`, default: `false`).
If specified, the following element:
```html
```
...has the following `data`:
```js
{ position:
{ opening:
{ start: { line: 1, column: 1, offset: 0 },
end: { line: 1, column: 18, offset: 17 } },
closing: null,
properties:
{ src:
{ start: { line: 1, column: 6, offset: 5 },
end: { line: 1, column: 13, offset: 12 } },
alt:
{ start: { line: 1, column: 14, offset: 13 },
end: { line: 1, column: 17, offset: 16 } } } } }
```
### `parse.Parser`
Access to the [parser][], if you need it.
## License
[MIT][license] Β© [Titus Wormer][author]
[build-badge]: https://img.shields.io/travis/rehypejs/rehype/master.svg
[build]: https://travis-ci.org/rehypejs/rehype
[coverage-badge]: https://img.shields.io/codecov/c/github/rehypejs/rehype.svg
[coverage]: https://codecov.io/github/rehypejs/rehype
[downloads-badge]: https://img.shields.io/npm/dm/rehype-parse.svg
[downloads]: https://www.npmjs.com/package/rehype-parse
[size-badge]: https://img.shields.io/bundlephobia/minzip/rehype-parse.svg
[size]: https://bundlephobia.com/result?p=rehype-parse
[chat-badge]: https://img.shields.io/badge/join%20the%20community-on%20spectrum-7b16ff.svg
[chat]: https://spectrum.chat/unified/rehype
[license]: https://github.com/rehypejs/rehype/blob/master/license
[author]: https://wooorm.com
[npm]: https://docs.npmjs.com/cli/install
[rehype-remark]: https://github.com/rehypejs/rehype-remark
[remark-stringify]: https://github.com/remarkjs/remark/tree/master/packages/remark-stringify
[unified]: https://github.com/unifiedjs/unified
[vfile]: https://github.com/vfile/vfile
[parse-errors]: https://html.spec.whatwg.org/multipage/parsing.html#parse-errors
[processor]: https://github.com/rehypejs/rehype/blob/master/packages/rehype
[hast]: https://github.com/syntax-tree/hast
[parser]: https://github.com/unifiedjs/unified#processorparser
[announcement]: https://medium.com/unifiedjs/collectively-evolving-through-crowdsourcing-22c359ea95cc
