unist utility to assert nodes
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[unist][] utility to assert trees.
* What is this?
* When should I use this?
* Install
* Use
* API
* [assert(tree[, parent])](#asserttree-parent)
* [parent(tree[, parent])](#parenttree-parent)
* [literal(node[, parent])](#literalnode-parent)
* [_void(node[, parent])](#_voidnode-parent)
* wrap(fn)
* AssertionError
* Extensions
* Types
* Compatibility
* Related
* Contribute
* License
This package is a tiny utility that helps you deal with nodes.
This utility is typically useful when you expect certain nodes in your APIs
and want to make sure they’re valid and as expected.
Different utilities, [mdast-util-assert][mdast-util-assert],
[hast-util-assert][hast-util-assert], and [nlcst-test][nlcst-test],
do the same but for mdast, hast, and nlcst nodes, respectively.
This package is [ESM only][esm].
In Node.js (version 16+), install with [npm][]:
``sh`
npm install unist-util-assert
In Deno with [esm.sh][esmsh]:
`js`
import {assert} from 'https://esm.sh/unist-util-assert@4'
In browsers with [esm.sh][esmsh]:
`html`
`js
import {_void, assert, parent} from 'unist-util-assert'
assert({type: 'root', children: []})
assert({type: 'break'})
assert({type: 'element', properties: {}, children: []})
// All OK.
assert({children: []})
// AssertionError: node should have a type: { children: [] }
parent({type: 'break'})
// AssertionError: parent should have children: { type: 'break' }
assert({type: 'element', properties: function() {}})
// AssertionError: non-specced property properties should be JSON: { type: 'element', properties: [Function] }
_void({type: 'text', value: 'Alpha'})
// AssertionError: void should not have value: { type: 'text', value: 'Alpha' }
assert({type: 'paragraph', children: ['foo']})
// AssertionError: node should be an object: 'foo' in { type: 'paragraph', children: [ 'foo' ] }`
This package exports the identifiers [_void][void], [assert][assert],literal
[][literal], [parent][parent], and [wrap][wrap].
There is no default export.
Assert that tree is a valid unist [Node][node].
If tree is a parent, all children will be asserted too.
###### Parameters
* tree (unknown)parent
— thing to assert
* ([Parent][parent-node], optional)
— optional, valid parent
###### Returns
Nothing.
###### Throws
When tree (or its descendants) is not a node.
Assert that tree is a valid unist [Parent][parent-node].
All children will be asserted too.
###### Parameters
* tree (unknown)parent
— thing to assert
* ([Parent][parent-node], optional)
— optional, valid parent
###### Returns
Nothing.
###### Throws
When tree is not a parent or its descendants are not nodes.
Assert that node is a valid unist [Literal][literal-node].
###### Parameters
* tree (unknown)parent
— thing to assert
* ([Parent][parent-node], optional)
— optional, valid parent
###### Returns
Nothing.
###### Throws
When node is not a literal.
Assert that node is a valid void node.
###### Parameters
* tree (unknown)parent
— thing to assert
* ([Parent][parent-node], optional)
— optional, valid parent
###### Returns
Nothing.
###### Throws
When node is not a node, a parent, or a literal.
Wrapper that adds the current node (and parent, if available) to error
messages.
###### Parameters
* fn ((node?: any, parent?: Parent | null | undefined) => asserts node is Node))
— custom assertion
###### Returns
Wrapped fn.
Assertion error from node:assert (TypeScript type).
###### Type
`ts`
type AssertionError = import('node:assert').AssertionError
This module can be used as a base to test subsets of unist (for an example, see
[mdast-util-assert][mdast-util-assert]).wrap
All functions that are exposed from such a module, and functions used internally
to test children, should be wrapped in , which adds an inspectable string
of the respective node, and its parent when available, to the exposed error
message.
This package is fully typed with [TypeScript][].
It exports the additional type [AssertionError][assertionerror].
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, unist-util-assert@^4,
compatible with Node.js 16.
* [mdast-util-assert][mdast-util-assert]hast-util-assert
— assert mdast nodes
* nlcst-test
— assert hast nodes
*
— assert nlcst nodes
See [contributing.md][contributing] in [syntax-tree/.github][health] forsupport.md`][support] for ways to get help.
ways to get started.
See [
This project has a [code of conduct][coc].
By interacting with this repository, organization, or community you agree to
abide by its terms.
[MIT][license] © [Titus Wormer][author]
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[coverage]: https://codecov.io/github/syntax-tree/unist-util-assert
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[downloads]: https://www.npmjs.com/package/unist-util-assert
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[sponsors-badge]: https://opencollective.com/unified/sponsors/badge.svg
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[collective]: https://opencollective.com/unified
[chat-badge]: https://img.shields.io/badge/chat-discussions-success.svg
[chat]: https://github.com/syntax-tree/unist/discussions
[npm]: https://docs.npmjs.com/cli/install
[esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c
[esmsh]: https://esm.sh
[typescript]: https://www.typescriptlang.org
[license]: license
[author]: https://wooorm.com
[health]: https://github.com/syntax-tree/.github
[contributing]: https://github.com/syntax-tree/.github/blob/main/contributing.md
[support]: https://github.com/syntax-tree/.github/blob/main/support.md
[coc]: https://github.com/syntax-tree/.github/blob/main/code-of-conduct.md
[unist]: https://github.com/syntax-tree/unist
[node]: https://github.com/syntax-tree/unist#node
[parent-node]: https://github.com/syntax-tree/unist#parent
[literal-node]: https://github.com/syntax-tree/unist#literal
[mdast-util-assert]: https://github.com/syntax-tree/mdast-util-assert
[hast-util-assert]: https://github.com/syntax-tree/hast-util-assert
[nlcst-test]: https://github.com/syntax-tree/nlcst-test
[assert]: #asserttree-parent
[parent]: #parenttree-parent
[literal]: #literalnode-parent
[void]: #_voidnode-parent
[wrap]: #wrapfn
[assertionerror]: #assertionerror