269 lines
6.1 KiB
Markdown
269 lines
6.1 KiB
Markdown
# estree-util-scope
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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 to check what’s defined in a scope.
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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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* [`Scope`](#scope)
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* [`Visitors`](#visitors)
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* [`createVisitors()`](#createvisitors)
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* [Examples](#examples)
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* [Example: just the top scope](#example-just-the-top-scope)
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* [Compatibility](#compatibility)
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* [Related](#related)
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* [Security](#security)
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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 tracks what’s defined in a scope.
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## When should I use this?
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If you are walking an estree already and want to find out what’s defined,
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use this.
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If you have more complex scoping needs,
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see [`eslint-scope`][github-eslint-scope].
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## Install
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This package is [ESM only][esm].
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In Node.js (version 16+), install with [npm][]:
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```sh
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npm install estree-util-scope
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```
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In Deno with [`esm.sh`][esmsh]:
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```js
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import {createVisitors} from 'https://esm.sh/estree-util-scope@1'
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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 {createVisitors} from 'https://esm.sh/estree-util-scope@1?bundle'
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</script>
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```
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## Use
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Say we have the following `example.js`:
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```js
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/**
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* @import {Program} from 'estree'
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*/
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import {Parser} from 'acorn'
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import {createVisitors} from 'estree-util-scope'
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import {walk} from 'estree-walker'
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const tree = /** @type {Program} */ (
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Parser.parse('import {a} from "b"; const c = 1', {
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ecmaVersion: 'latest',
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sourceType: 'module'
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})
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)
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const visitors = createVisitors()
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walk(tree, {enter: visitors.enter, leave: visitors.exit})
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console.log(visitors.scopes.at(-1))
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```
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…now running `node example.js` yields:
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```js
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{ block: false, defined: [ 'a', 'c' ] }
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```
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## API
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### `Scope`
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Scope.
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###### Fields
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* `block` (`boolean`)
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— whether this is a block scope or not;
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blocks are things made by `for` and `try` and `if`;
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non-blocks are functions and the top-level scope
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* `defined` (`Array<string>`)
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— identifiers that are defined in this scope
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### `Visitors`
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State to track what’s defined;
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contains `enter`, `exit` callbacks you must call and `scopes`.
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###### Fields
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* `enter` (`(node: Node) => undefined`)
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— callback you must call when entering a node
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* `exit` (`(node: Node) => undefined`)
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— callback you must call when exiting (leaving) a node
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* `scopes` (`[topLevel: Scope, ...rest: Scope[]]`)
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— list of scopes;
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the first scope is the top-level scope;
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the last scope is the current scope
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### `createVisitors()`
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Create state to track what’s defined.
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###### Parameters
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There are no parameters.
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###### Returns
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State (`Visitors`).
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## Examples
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### Example: just the top scope
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Sometimes, you only care about a top-scope.
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Or otherwise want to skip a node.
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How to do this depends on how you walk the tree.
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With `estree-walker`,
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you can skip by calling `this.skip`.
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```js
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/**
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* @import {Program} from 'estree'
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*/
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import {Parser} from 'acorn'
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import {createVisitors} from 'estree-util-scope'
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import {walk} from 'estree-walker'
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const tree = /** @type {Program} */ (
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Parser.parse(
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'function a(b) { var c = 1; if (d) { var e = 2 } }; if (f) { var g = 2 }',
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{ecmaVersion: 'latest'}
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)
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)
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const visitors = createVisitors()
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walk(tree, {
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enter(node) {
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visitors.enter(node)
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if (
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node.type === 'ArrowFunctionExpression' ||
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node.type === 'FunctionDeclaration' ||
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node.type === 'FunctionExpression'
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) {
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this.skip()
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visitors.exit(node) // Call the exit handler manually.
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}
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},
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leave: visitors.exit
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})
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console.log(visitors.scopes.at(-1))
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```
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…yields:
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```js
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{ block: false, defined: [ 'a', 'g' ] }
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```
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## Compatibility
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Projects maintained by the unified collective are compatible with maintained
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versions of Node.js.
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When we cut a new major release, we drop support for unmaintained versions of
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Node.
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This means we try to keep the current release line, `estree-util-scope@1`,
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compatible with Node.js 16.
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## Related
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## Security
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This package is safe.
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## Contribute
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See [`contributing.md` in `syntax-tree/.github`][contributing] for ways to get
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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-scope/workflows/main/badge.svg
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[build]: https://github.com/syntax-tree/estree-util-scope/actions
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[coverage-badge]: https://img.shields.io/codecov/c/github/syntax-tree/estree-util-scope.svg
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[coverage]: https://codecov.io/github/syntax-tree/estree-util-scope
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[downloads-badge]: https://img.shields.io/npm/dm/estree-util-scope.svg
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[downloads]: https://www.npmjs.com/package/estree-util-scope
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[size-badge]: https://img.shields.io/badge/dynamic/json?label=minzipped%20size&query=$.size.compressedSize&url=https://deno.bundlejs.com/?q=estree-util-scope
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[size]: https://bundlejs.com/?q=estree-util-scope
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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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[esm]: https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c
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[npm]: https://docs.npmjs.com/cli/install
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[esmsh]: https://esm.sh
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[license]: license
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[author]: https://wooorm.com
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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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[estree]: https://github.com/estree/estree
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[github-eslint-scope]: https://github.com/eslint/eslint-scope
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