# vfile-message

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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[, place][, origin])`](#vfilemessagereason-place-origin)
    *   [Well-known fields](#well-known-fields)
*   [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 14.14+, 16.0+), install with [npm][]:

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

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

```js
import {VFileMessage} from 'https://esm.sh/vfile-message@3'
```

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

```html
<script type="module">
  import {VFileMessage} from 'https://esm.sh/vfile-message@3?bundle'
</script>
```

## Use

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

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

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,
  source: 'spell',
  ruleId: 'typo',
  position: {start: {line: 1, column: 8}, end: {line: null, column: null}}
}
```

## API

This package exports the identifier `VFileMessage`.
There is no default export.

### `VFileMessage(reason[, place][, origin])`

Create a message for `reason` at `place` from `origin`.
When an error is passed in as `reason`, the `stack` is copied.

##### Parameters

###### `reason`

Reason for message (`string` or `Error`).
Uses the stack and message of the error if given.

###### `place`

Place at which the message occurred in a file ([`Node`][node],
[`Position`][position], or [`Point`][point], optional).

###### `origin`

Place in code the message originates from (`string`, optional).

Can either be the [`ruleId`][ruleid] (`'rule'`), or a string with both a
[`source`][source] and a [`ruleId`][ruleid] delimited with a colon
(`'source:rule'`).

##### Extends

[`Error`][error].

##### Returns

An instance of itself.

##### Properties

###### `reason`

Reason for message (`string`).

###### `fatal`

Whether this is a fatal problem that marks an associated file as no longer
processable (`boolean?`).
If `true`, marks associated file as no longer processable.
If `false`, necessitates a (potential) change.
The value can also be `null` or `undefined`, for things that might not need
changing.

###### `line`

Starting line of error (`number?`).

###### `column`

Starting column of error (`number?`).

###### `position`

Full range information, when available ([`Position`][position]).
Has `start` and `end` properties, both set to an object with `line` and
`column`, set to `number?`.

###### `source`

Namespace of message (`string?`, example: `'my-package'`).

###### `ruleId`

Category of message (`string?`, example: `'my-rule-name'`).

###### `stack`

Stack of message (`string?`).

###### `file`

Path of a file (used throughout the vfile ecosystem).

### Well-known fields

It’s OK to store custom data directly on the `VFileMessage`, some of those are
handled by [utilities][util].

###### `actual`

Specify the source value that’s being reported, which is deemed incorrect
(`string?`).

###### `expected`

Suggest values that should be used instead of `actual`, one or more values that
are deemed as acceptable (`(string|Array<string>)?`)

###### `url`

Link to documentation for the message (`string`).

###### `note`

Long form description of the message (supported by
[`vfile-reporter`][reporter]).

## Types

This package is fully typed with [TypeScript][].
It exports no 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 14.14+ and 16.0+.
Our projects sometimes work with older versions, but this is not guaranteed.

## 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/bundlephobia/minzip/vfile-message.svg

[size]: https://bundlephobia.com/result?p=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

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

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

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

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

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

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

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

[ruleid]: #ruleid

[source]: #source