233 lines
6.2 KiB
Markdown
233 lines
6.2 KiB
Markdown
# estree-util-attach-comments
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[![Build][build-badge]][build]
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[![Coverage][coverage-badge]][coverage]
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[![Downloads][downloads-badge]][downloads]
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[![Size][size-badge]][size]
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[![Sponsors][sponsors-badge]][collective]
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[![Backers][backers-badge]][collective]
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[![Chat][chat-badge]][chat]
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[estree][] utility attach semistandard comment nodes (such as from [acorn][]) to
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the nodes in that tree.
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## Contents
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* [What is this?](#what-is-this)
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* [When should I use this?](#when-should-i-use-this)
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* [Install](#install)
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* [Use](#use)
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* [API](#api)
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* [`attachComments(tree, comments)`](#attachcommentstree-comments)
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* [Types](#types)
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* [Compatibility](#compatibility)
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* [Contribute](#contribute)
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* [License](#license)
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## What is this?
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This package is a utility that you can use to embed comment nodes *inside* a
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tree.
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This is useful because certain estree parsers give you an array (espree and
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acorn) whereas other estree tools expect comments to be embedded on nodes in the
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tree.
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This package uses one `comments` array where each comment has `leading` and
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`trailing` fields, as applied by `acorn`, but does not support the slightly
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different non-standard comments made by `espree`.
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## When should I use this?
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You can use this package when working with comments from Acorn and later working
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with a tool such as recast or Babel.
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## Install
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This package is [ESM only][esm].
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In Node.js (version 14.14+ and 16.0+), install with [npm][]:
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```sh
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npm install estree-util-attach-comments
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```
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In Deno with [`esm.sh`][esmsh]:
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```js
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import {attachComments} from 'https://esm.sh/estree-util-attach-comments@2'
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```
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In browsers with [`esm.sh`][esmsh]:
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```html
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<script type="module">
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import {attachComments} from 'https://esm.sh/estree-util-attach-comments@2?bundle'
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</script>
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```
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## Use
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Say our document `index.js` contains:
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```js
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/* 1 */ function /* 2 */ a /* 3 */ (/* 4 */b) /* 5 */ { /* 6 */ return /* 7 */ b + /* 8 */ 1 /* 9 */ }
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```
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…and our module `example.js` looks as follows:
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```js
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import fs from 'node:fs/promises'
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import * as acorn from 'acorn'
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import recast from 'recast'
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import {attachComments} from 'estree-util-attach-comments'
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const code = String(await fs.readFile('index.js'))
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const comments = []
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const tree = acorn.parse(code, {ecmaVersion: 2020, onComment: comments})
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attachComments(tree, comments)
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console.log(recast.print(tree).code)
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```
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Yields:
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```js
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/* 1 */
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function /* 2 */
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a(
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/* 3 */
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/* 4 */
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b
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) /* 5 */
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{
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/* 6 */
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return (
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/* 7 */
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b + /* 8 */
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1
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);
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}/* 9 */
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```
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> 👉 **Note**: the lines are added by `recast` in this case.
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> And, some of these weird comments are off, but they’re pretty close.
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## API
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This package exports the identifier [`attachComments`][attachcomments].
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There is no default export.
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### `attachComments(tree, comments)`
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Attach semistandard estree comment nodes to the tree.
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This mutates the given [`tree`][estree].
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It takes `comments`, walks the tree, and adds comments as close as possible
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to where they originated.
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Comment nodes are given two boolean fields: `leading` (`true` for `/* a */ b`)
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and `trailing` (`true` for `a /* b */`).
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Both fields are `false` for dangling comments: `[/* a */]`.
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This is what `recast` uses too, and is somewhat similar to Babel, which is not
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estree but instead uses `leadingComments`, `trailingComments`, and
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`innerComments` arrays on nodes.
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The algorithm checks any node: even recent (or future) proposals or nonstandard
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syntax such as JSX, because it ducktypes to find nodes instead of having a list
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of visitor keys.
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The algorithm supports `loc` fields (line/column), `range` fields (offsets),
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and direct `start` / `end` fields.
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###### Parameters
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* `tree` ([`Program`][program])
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— tree to attach to
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* `comments` (`Array<EstreeComment>`)
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— list of comments
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###### Returns
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The given `tree` ([`Program`][program]).
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## Types
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This package is fully typed with [TypeScript][].
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It exports no additional types.
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## Compatibility
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Projects maintained by the unified collective are compatible with all maintained
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versions of Node.js.
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As of now, that is Node.js 14.14+ and 16.0+.
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Our projects sometimes work with older versions, but this is not guaranteed.
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## Contribute
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See [`contributing.md`][contributing] in [`syntax-tree/.github`][health] for
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ways to get started.
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See [`support.md`][support] for ways to get help.
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This project has a [code of conduct][coc].
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By interacting with this repository, organization, or community you agree to
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abide by its terms.
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## License
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[MIT][license] © [Titus Wormer][author]
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<!-- Definitions -->
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[build-badge]: https://github.com/syntax-tree/estree-util-attach-comments/workflows/main/badge.svg
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[build]: https://github.com/syntax-tree/estree-util-attach-comments/actions
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[coverage-badge]: https://img.shields.io/codecov/c/github/syntax-tree/estree-util-attach-comments.svg
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[coverage]: https://codecov.io/github/syntax-tree/estree-util-attach-comments
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[downloads-badge]: https://img.shields.io/npm/dm/estree-util-attach-comments.svg
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[downloads]: https://www.npmjs.com/package/estree-util-attach-comments
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[size-badge]: https://img.shields.io/bundlephobia/minzip/estree-util-attach-comments.svg
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[size]: https://bundlephobia.com/result?p=estree-util-attach-comments
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[sponsors-badge]: https://opencollective.com/unified/sponsors/badge.svg
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[backers-badge]: https://opencollective.com/unified/backers/badge.svg
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[collective]: https://opencollective.com/unified
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[chat-badge]: https://img.shields.io/badge/chat-discussions-success.svg
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[chat]: https://github.com/syntax-tree/unist/discussions
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[npm]: https://docs.npmjs.com/cli/install
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[esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c
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[esmsh]: https://esm.sh
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[typescript]: https://www.typescriptlang.org
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[license]: license
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[author]: https://wooorm.com
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[health]: https://github.com/syntax-tree/.github
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[contributing]: https://github.com/syntax-tree/.github/blob/main/contributing.md
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[support]: https://github.com/syntax-tree/.github/blob/main/support.md
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[coc]: https://github.com/syntax-tree/.github/blob/main/code-of-conduct.md
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[acorn]: https://github.com/acornjs/acorn
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[estree]: https://github.com/estree/estree
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[program]: https://github.com/estree/estree/blob/master/es5.md#programs
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[attachcomments]: #attachcommentstree-comments
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