unist-util-assert

unist utility to assert trees.

Contents

• What is this?
• When should I use this?
• Install
• Use
• API
  • assert(node[, parent])
  • parent(node[, parent])
  • literal(node[, parent])
  • _void(node[, parent])
  • wrap(fn)
• Extensions
• Types
• Compatibility
• Related
• Contribute
• License

What is this?

This package is a tiny utility that helps you deal with nodes.

When should I use this?

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, hast-util-assert, and nlcst-test, do the same but for mdast, hast, and nlcst nodes, respectively.

Install

This package is ESM only. In Node.js (version 12.20+, 14.14+, 16.0+, or 18.0+), install with npm:

npm install unist-util-assert

In Deno with esm.sh:

import {assert} from 'https://esm.sh/unist-util-assert@3'

In browsers with esm.sh:

<script type="module">
  import {assert} from 'https://esm.sh/unist-util-assert@3?bundle'
</script>

Use

import {assert, parent, _void} 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' ] }`

API

This package exports the identifiers assert, parent, literal, _void, and wrap. There is no default export.

assert(node[, parent])

Assert that node is a valid unist Node. If tree is a parent, all children will be asserted as well.

Throws

When node, or one of its children, is not a valid node.

parent(node[, parent])

Assert that node is a valid unist Parent. All children will be asserted as well.

literal(node[, parent])

Assert that node is a valid unist Literal.

_void(node[, parent])

Assert that node is a valid unist Node, but neither Parent nor Literal.

wrap(fn)

Wraps fn (which is passed a node, and an optional parent node), so that any errors thrown inside it will contain information regarding the node (and the parent, when given).

Extensions

This module can be used as a base to test subsets of unist (for an example, see mdast-util-assert). All functions that are exposed from such a module, and functions used internally to test children, should be wrapped in wrap, which adds an inspectable string of the respective node, and its parent when available, to the exposed error message.

Types

This package is fully typed with TypeScript. It does not export additional types.

Compatibility

Projects maintained by the unified collective are compatible with all maintained versions of Node.js. As of now, that is Node.js 12.20+, 14.14+, 16.0+, and 18.0+. Our projects sometimes work with older versions, but this is not guaranteed.

Related

• mdast-util-assert — assert mdast nodes
• hast-util-assert — assert hast nodes
• nlcst-test — assert nlcst nodes

Contribute

See contributing.md in syntax-tree/.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