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Add regexp/prefer-set-operation rule (#616)
* Add `regexp/prefer-set-operation` rule * Create spotty-phones-deliver.md
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‎.changeset/spotty-phones-deliver.md

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---
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"eslint-plugin-regexp": major
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---
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Add `regexp/prefer-set-operation` rule

‎README.md

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@@ -165,6 +165,7 @@ The `plugin:regexp/all` config enables all rules. It's meant for testing, not fo
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| [prefer-range](https://ota-meshi.github.io/eslint-plugin-regexp/rules/prefer-range.html) | enforce using character class range | ✅ | | 🔧 | |
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| [prefer-regexp-exec](https://ota-meshi.github.io/eslint-plugin-regexp/rules/prefer-regexp-exec.html) | enforce that `RegExp#exec` is used instead of `String#match` if no global flag is provided | | | | |
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| [prefer-regexp-test](https://ota-meshi.github.io/eslint-plugin-regexp/rules/prefer-regexp-test.html) | enforce that `RegExp#test` is used instead of `String#match` and `RegExp#exec` | | | 🔧 | |
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| [prefer-set-operation](https://ota-meshi.github.io/eslint-plugin-regexp/rules/prefer-set-operation.html) | prefer character class set operations instead of lookarounds | ✅ | | 🔧 | |
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| [require-unicode-regexp](https://ota-meshi.github.io/eslint-plugin-regexp/rules/require-unicode-regexp.html) | enforce the use of the `u` flag | | | 🔧 | |
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| [require-unicode-sets-regexp](https://ota-meshi.github.io/eslint-plugin-regexp/rules/require-unicode-sets-regexp.html) | enforce the use of the `v` flag | | | 🔧 | |
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| [sort-alternatives](https://ota-meshi.github.io/eslint-plugin-regexp/rules/sort-alternatives.html) | sort alternatives if order doesn't matter | | | 🔧 | |

‎docs/rules/index.md

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| [prefer-range](prefer-range.md) | enforce using character class range | ✅ | | 🔧 | |
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| [prefer-regexp-exec](prefer-regexp-exec.md) | enforce that `RegExp#exec` is used instead of `String#match` if no global flag is provided | | | | |
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| [prefer-regexp-test](prefer-regexp-test.md) | enforce that `RegExp#test` is used instead of `String#match` and `RegExp#exec` | | | 🔧 | |
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| [prefer-set-operation](prefer-set-operation.md) | prefer character class set operations instead of lookarounds | ✅ | | 🔧 | |
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| [require-unicode-regexp](require-unicode-regexp.md) | enforce the use of the `u` flag | | | 🔧 | |
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| [require-unicode-sets-regexp](require-unicode-sets-regexp.md) | enforce the use of the `v` flag | | | 🔧 | |
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| [sort-alternatives](sort-alternatives.md) | sort alternatives if order doesn't matter | | | 🔧 | |

‎docs/rules/prefer-set-operation.md

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---
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pageClass: "rule-details"
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sidebarDepth: 0
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title: "regexp/prefer-set-operation"
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description: "prefer character class set operations instead of lookarounds"
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---
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# regexp/prefer-set-operation
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💼 This rule is enabled in the ✅ `plugin:regexp/recommended` config.
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🔧 This rule is automatically fixable by the [`--fix` CLI option](https://eslint.org/docs/latest/user-guide/command-line-interface#--fix).
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<!-- end auto-generated rule header -->
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> prefer character class set operations instead of lookarounds
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## :book: Rule Details
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Regular expressions with the `v` flag have access to character class set operations (e.g. `/[\s&&\p{ASCII}]/v`, `/[\w--\d]/v`). These are more readable and performant than using lookarounds to achieve the same effect. For example, `/(?!\d)\w/v` is the same as `/[\w--\d]/v`.
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<eslint-code-block fix>
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```js
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/* eslint regexp/prefer-set-operation: "error" */
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/* ✓ GOOD */
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var foo = /(?!\d)\w/ // requires the v flag
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var foo = /(?!\d)\w/u // requires the v flag
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/* ✗ BAD */
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var foo = /(?!\d)\w/v
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var foo = /(?!\s)[\w\P{ASCII}]/v
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```
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</eslint-code-block>
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## :wrench: Options
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Nothing.
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## :rocket: Version
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:exclamation: <badge text="This rule has not been released yet." vertical="middle" type="error"> ***This rule has not been released yet.*** </badge>
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## :mag: Implementation
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- [Rule source](https://github.com/ota-meshi/eslint-plugin-regexp/blob/master/lib/rules/prefer-set-operation.ts)
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- [Test source](https://github.com/ota-meshi/eslint-plugin-regexp/blob/master/tests/lib/rules/prefer-set-operation.ts)

‎lib/configs/recommended.ts

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"regexp/prefer-predefined-assertion": "error",
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"regexp/prefer-question-quantifier": "error",
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"regexp/prefer-range": "error",
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"regexp/prefer-set-operation": "error",
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"regexp/prefer-star-quantifier": "error",
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"regexp/prefer-unicode-codepoint-escapes": "error",
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"regexp/prefer-w": "error",

‎lib/rules/prefer-set-operation.ts

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import type { RegExpVisitor } from "@eslint-community/regexpp/visitor"
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import type {
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Alternative,
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Character,
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CharacterClass,
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CharacterSet,
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ExpressionCharacterClass,
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LookaroundAssertion,
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Node,
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} from "@eslint-community/regexpp/ast"
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import type { RegExpContext } from "../utils"
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import { createRule, defineRegexpVisitor } from "../utils"
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import { hasStrings } from "regexp-ast-analysis"
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type CharElement =
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| Character
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| CharacterSet
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| CharacterClass
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| ExpressionCharacterClass
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function isCharElement(node: Node): node is CharElement {
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return (
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node.type === "Character" ||
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node.type === "CharacterSet" ||
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node.type === "CharacterClass" ||
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node.type === "ExpressionCharacterClass"
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)
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}
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type CharLookaround = LookaroundAssertion & {
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alternatives: [Alternative & { elements: [CharElement] }]
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}
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function isCharLookaround(node: Node): node is CharLookaround {
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return (
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node.type === "Assertion" &&
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(node.kind === "lookahead" || node.kind === "lookbehind") &&
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node.alternatives.length === 1 &&
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node.alternatives[0].elements.length === 1 &&
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isCharElement(node.alternatives[0].elements[0])
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)
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}
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function escapeRaw(raw: string): string {
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if (/^[&\-^]$/u.test(raw)) {
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return `\\${raw}`
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}
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return raw
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}
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export default createRule("prefer-set-operation", {
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meta: {
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docs: {
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description:
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"prefer character class set operations instead of lookarounds",
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category: "Best Practices",
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recommended: true,
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},
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fixable: "code",
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schema: [],
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messages: {
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unexpected:
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"This lookaround can be combined with '{{char}}' using a set operation.",
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},
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type: "suggestion",
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},
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create(context) {
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function createVisitor(
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regexpContext: RegExpContext,
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): RegExpVisitor.Handlers {
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const { node, flags, getRegexpLocation, fixReplaceNode } =
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regexpContext
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if (!flags.unicodeSets) {
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// set operations are exclusive to the v flag.
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return {}
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}
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function tryApply(
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element: CharElement,
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assertion: CharLookaround,
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parent: Alternative,
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): void {
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const assertElement = assertion.alternatives[0].elements[0]
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if (hasStrings(assertElement, flags)) {
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return
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}
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context.report({
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node,
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loc: getRegexpLocation(assertion),
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messageId: "unexpected",
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data: {
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char: element.raw,
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},
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fix: fixReplaceNode(parent, () => {
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const op = assertion.negate ? "--" : "&&"
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const left = escapeRaw(element.raw)
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const right = escapeRaw(assertElement.raw)
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const replacement = `[${left}${op}${right}]`
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return parent.elements
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.map((e) => {
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if (e === assertion) {
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return ""
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} else if (e === element) {
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return replacement
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}
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return e.raw
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})
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.join("")
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}),
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})
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}
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return {
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onAlternativeEnter(alternative) {
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const { elements } = alternative
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for (let i = 1; i < elements.length; i++) {
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const a = elements[i - 1]
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const b = elements[i]
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if (
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isCharElement(a) &&
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isCharLookaround(b) &&
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b.kind === "lookbehind"
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) {
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tryApply(a, b, alternative)
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}
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if (
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isCharLookaround(a) &&
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a.kind === "lookahead" &&
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isCharElement(b)
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) {
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tryApply(b, a, alternative)
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}
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}
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},
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}
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}
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return defineRegexpVisitor(context, {
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createVisitor,
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})
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},
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})

‎lib/utils/rules.ts

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import preferRegexpExec from "../rules/prefer-regexp-exec"
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import preferRegexpTest from "../rules/prefer-regexp-test"
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import preferResultArrayGroups from "../rules/prefer-result-array-groups"
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import preferSetOperation from "../rules/prefer-set-operation"
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import preferStarQuantifier from "../rules/prefer-star-quantifier"
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import preferT from "../rules/prefer-t"
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import preferUnicodeCodepointEscapes from "../rules/prefer-unicode-codepoint-escapes"
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preferRegexpExec,
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preferRegexpTest,
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preferResultArrayGroups,
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preferSetOperation,
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preferStarQuantifier,
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preferT,
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preferUnicodeCodepointEscapes,

‎tests/lib/rules/prefer-set-operation.ts

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import { RuleTester } from "eslint"
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import rule from "../../../lib/rules/prefer-set-operation"
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const tester = new RuleTester({
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parserOptions: {
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ecmaVersion: "latest",
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sourceType: "module",
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},
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})
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tester.run("prefer-set-operation", rule as any, {
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valid: [
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String.raw`/a\b/`,
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String.raw`/a\b/u`,
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String.raw`/a\b/v`,
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String.raw`/(?!a)\w/`,
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String.raw`/(?!a)\w/u`,
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],
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invalid: [
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{
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code: String.raw`/(?!a)\w/v`,
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output: String.raw`/[\w--a]/v`,
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errors: [
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"This lookaround can be combined with '\\w' using a set operation.",
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],
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},
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{
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code: String.raw`/\w(?<=\d)/v`,
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output: String.raw`/[\w&&\d]/v`,
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errors: [
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"This lookaround can be combined with '\\w' using a set operation.",
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],
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},
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{
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code: String.raw`/(?!-)&/v`,
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output: String.raw`/[\&--\-]/v`,
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errors: [
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"This lookaround can be combined with '&' using a set operation.",
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],
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},
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],
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})

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