# vfile-message

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[![Downloads][downloads-badge]][downloads]
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Create [vfile][] messages.

## Contents

*   [What is this?](#what-is-this)
*   [When should I use this?](#when-should-i-use-this)
*   [Install](#install)
*   [Use](#use)
*   [API](#api)
    *   [`VFileMessage(reason[, options])`](#vfilemessagereason-options)
    *   [`Options`](#options)
    *   [Well-known](#well-known)
*   [Types](#types)
*   [Compatibility](#compatibility)
*   [Contribute](#contribute)
*   [License](#license)

## What is this?

This package provides a (lint) message format.

## When should I use this?

In most cases, you can use `file.message` from `VFile` itself, but in some
cases you might not have a file, and still want to emit warnings or errors,
in which case this can be used directly.

## Install

This package is [ESM only][esm].
In Node.js (version 16+), install with [npm][]:

```sh
npm install vfile-message
```

In Deno with [`esm.sh`][esmsh]:

```js
import {VFileMessage} from 'https://esm.sh/vfile-message@4'
```

In browsers with [`esm.sh`][esmsh]:

```html
<script type="module">
  import {VFileMessage} from 'https://esm.sh/vfile-message@4?bundle'
</script>
```

## Use

```js
import {VFileMessage} from 'vfile-message'

const message = new VFileMessage(
  'Unexpected unknown word `braavo`, did you mean `bravo`?',
  {source: 'spell', ruleId: 'typo', place: {line: 1, column: 8}}
)

console.log(message)
```

Yields:

```txt
[1:8: Unexpected unknown word `braavo`, did you mean `bravo`?] {
  reason: 'Unexpected unknown word `braavo`, did you mean `bravo`?',
  line: 1,
  column: 8,
  ancestors: undefined,
  cause: undefined,
  fatal: undefined,
  place: {line: 1, column: 8},
  ruleId: 'typo',
  source: 'spell'
}
```

## API

This package exports the identifier [`VFileMessage`][api-vfile-message].
There is no default export.

### `VFileMessage(reason[, options])`

Create a message for `reason`.

> 🪦 **Note**: also has obsolete signatures.

###### Parameters

*   `reason` (`string`)
    — reason for message (should use markdown)
*   `options` ([`Options`][api-options], optional)
    — configuration.

###### Extends

[`Error`][mdn-error].

###### Returns

Instance of `VFileMessage`.

###### Fields

*   `ancestors` ([`Array<Node>`][unist-node] or `undefined`)
    — stack of (inclusive) ancestor nodes surrounding the message
*   `cause` ([`Error`][mdn-error] or `undefined`)
    — original error cause of the message
*   `column` (`number` or `undefined`)
    — starting column of message
*   `fatal` (`boolean` or `undefined`)
    — state of problem; `true`: error, file not usable; `false`: warning,
    change may be needed; `undefined`: info, change likely not needed
*   `line` (`number` or `undefined`)
    — starting line of message
*   `place` ([`Point`][unist-point], [`Position`][unist-position] or `undefined`)
    — place of message
*   `reason` (`string`)
    — reason for message (should use markdown)
*   `ruleId` (`string` or `undefined`, example: `'my-rule'`)
    — category of message
*   `source` (`string` or `undefined`, example: `'my-package'`)
    — namespace of message

### `Options`

Configuration (TypeScript type).

###### Fields

*   `ancestors` ([`Array<Node>`][unist-node], optional)
    — stack of (inclusive) ancestor nodes surrounding the message
*   `cause` ([`Error`][mdn-error], optional)
    — original error cause of the message
*   `place` ([`Point`][unist-point] or [`Position`][unist-position], optional)
    — place of message
*   `ruleId` (`string`, optional, example: `'my-rule'`)
    — category of message
*   `source` (`string`, optional, , example: `'my-package'`)
    — namespace of who sent the message

### Well-known

It’s OK to store custom data directly on the `VFileMessage`, some of those are
handled by [utilities][util].
The following fields are documented and typed here.

###### Fields

*   `actual` (`string`, optional)
    — specify the source value that’s being reported, which is deemed incorrect
*   `expected` (`Array<string>`, optional)
    — suggest acceptable values that can be used instead of `actual`
*   `url` (`string`, optional)
    — link to docs for the message (this must be an absolute URL that can be
    passed as `x` to `new URL(x)`)
*   `note` (`string`, optional)
    — long form description of the message (you should use markdown)

## Types

This package is fully typed with [TypeScript][].
It exports the additional type [`Options`][api-options].

## Compatibility

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, `vfile-message@^4`,
compatible with Node.js 16.

## Contribute

See [`contributing.md`][contributing] in [`vfile/.github`][health] for ways to
get started.
See [`support.md`][support] for ways to get help.

This project has a [code of conduct][coc].
By interacting with this repository, organization, or community you agree to
abide by its terms.

## License

[MIT][license] © [Titus Wormer][author]

<!-- Definitions -->

[build-badge]: https://github.com/vfile/vfile-message/workflows/main/badge.svg

[build]: https://github.com/vfile/vfile-message/actions

[coverage-badge]: https://img.shields.io/codecov/c/github/vfile/vfile-message.svg

[coverage]: https://codecov.io/github/vfile/vfile-message

[downloads-badge]: https://img.shields.io/npm/dm/vfile-message.svg

[downloads]: https://www.npmjs.com/package/vfile-message

[size-badge]: https://img.shields.io/badge/dynamic/json?label=minzipped%20size&query=$.size.compressedSize&url=https://deno.bundlejs.com/?q=vfile-message

[size]: https://bundlejs.com/?q=vfile-message

[sponsors-badge]: https://opencollective.com/unified/sponsors/badge.svg

[backers-badge]: https://opencollective.com/unified/backers/badge.svg

[collective]: https://opencollective.com/unified

[chat-badge]: https://img.shields.io/badge/chat-discussions-success.svg

[chat]: https://github.com/vfile/vfile/discussions

[npm]: https://docs.npmjs.com/cli/install

[contributing]: https://github.com/vfile/.github/blob/main/contributing.md

[support]: https://github.com/vfile/.github/blob/main/support.md

[health]: https://github.com/vfile/.github

[coc]: https://github.com/vfile/.github/blob/main/code-of-conduct.md

[esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c

[esmsh]: https://esm.sh

[typescript]: https://www.typescriptlang.org

[license]: license

[author]: https://wooorm.com

[mdn-error]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error

[unist-node]: https://github.com/syntax-tree/unist#node

[unist-point]: https://github.com/syntax-tree/unist#point

[unist-position]: https://github.com/syntax-tree/unist#position

[vfile]: https://github.com/vfile/vfile

[util]: https://github.com/vfile/vfile#utilities

[api-options]: #options

[api-vfile-message]: #vfilemessagereason-options