Make no-useless-escape fixable (#226)

* Make `no-useless-escape` fixable

* Update lib/rules/no-useless-escape.ts

Co-authored-by: Yosuke Ota <[email protected]>

Co-authored-by: Yosuke Ota <[email protected]>

Author: RunDevelopment

README.md

@@ -155,7 +155,7 @@ The rules with the following star :star: are included in the `plugin:regexp/reco
 | [regexp/hexadecimal-escape](https://ota-meshi.github.io/eslint-plugin-regexp/rules/hexadecimal-escape.html) | enforce consistent usage of hexadecimal escape | :wrench: |
 | [regexp/letter-case](https://ota-meshi.github.io/eslint-plugin-regexp/rules/letter-case.html) | enforce into your favorite case | :wrench: |
 | [regexp/match-any](https://ota-meshi.github.io/eslint-plugin-regexp/rules/match-any.html) | enforce match any character style | :star::wrench: |
-| [regexp/no-useless-escape](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-useless-escape.html) | disallow unnecessary escape characters in RegExp |  |
+| [regexp/no-useless-escape](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-useless-escape.html) | disallow unnecessary escape characters in RegExp | :wrench: |
 | [regexp/no-useless-non-capturing-group](https://ota-meshi.github.io/eslint-plugin-regexp/rules/no-useless-non-capturing-group.html) | disallow unnecessary Non-capturing group | :wrench: |
 | [regexp/order-in-character-class](https://ota-meshi.github.io/eslint-plugin-regexp/rules/order-in-character-class.html) | enforces elements order in character class | :wrench: |
 | [regexp/prefer-character-class](https://ota-meshi.github.io/eslint-plugin-regexp/rules/prefer-character-class.html) | enforce using character class | :wrench: |

docs/rules/README.md

@@ -69,7 +69,7 @@ The rules with the following star :star: are included in the `plugin:regexp/reco
 | [regexp/hexadecimal-escape](./hexadecimal-escape.md) | enforce consistent usage of hexadecimal escape | :wrench: |
 | [regexp/letter-case](./letter-case.md) | enforce into your favorite case | :wrench: |
 | [regexp/match-any](./match-any.md) | enforce match any character style | :star::wrench: |
-| [regexp/no-useless-escape](./no-useless-escape.md) | disallow unnecessary escape characters in RegExp |  |
+| [regexp/no-useless-escape](./no-useless-escape.md) | disallow unnecessary escape characters in RegExp | :wrench: |
 | [regexp/no-useless-non-capturing-group](./no-useless-non-capturing-group.md) | disallow unnecessary Non-capturing group | :wrench: |
 | [regexp/order-in-character-class](./order-in-character-class.md) | enforces elements order in character class | :wrench: |
 | [regexp/prefer-character-class](./prefer-character-class.md) | enforce using character class | :wrench: |

docs/rules/no-useless-escape.md

@@ -9,12 +9,14 @@ since: "v0.4.0"
 
 > disallow unnecessary escape characters in RegExp
 
+- :wrench: The `--fix` option on the [command line](https://eslint.org/docs/user-guide/command-line-interface#fixing-problems) can automatically fix some of the problems reported by this rule.
+
 ## :book: Rule Details
 
 This rule reports unnecessary escape characters in RegExp.  
 You may be able to find another mistake by finding unnecessary escapes.
 
-<eslint-code-block>
+<eslint-code-block fix>
 
 ```js
 /* eslint regexp/no-useless-escape: "error" */
@@ -34,7 +36,7 @@ var foo = /\u{[41]}/
 
 This rule checks for unnecessary escapes with deeper regular expression parsing than the ESLint core's [no-useless-escape] rule.
 
-<eslint-code-block>
+<eslint-code-block fix>
 
 ```js
 /* eslint no-useless-escape: "error" */

lib/rules/no-useless-escape.ts

@@ -46,6 +46,8 @@ const REGEX_ESCAPES = new Set([
     CP_CLOSING_PAREN, // )
 ])
 
+const POTENTIAL_ESCAPE_SEQUENCE = new Set("uxkpP")
+
 export default createRule("no-useless-escape", {
     meta: {
         docs: {
@@ -55,6 +57,7 @@ export default createRule("no-useless-escape", {
             // recommended: true,
             recommended: false,
         },
+        fixable: "code",
         schema: [],
         messages: {
             unnecessary: "Unnecessary escape character: \\{{character}}.",
@@ -68,12 +71,14 @@ export default createRule("no-useless-escape", {
         function createVisitor({
             node,
             getRegexpLocation,
+            fixReplaceNode,
         }: RegExpContext): RegExpVisitor.Handlers {
             /** Report */
             function report(
                 cNode: Character,
                 offset: number,
                 character: string,
+                fix: boolean,
             ) {
                 context.report({
                     node,
@@ -82,6 +87,7 @@ export default createRule("no-useless-escape", {
                     data: {
                         character,
                     },
+                    fix: fix ? fixReplaceNode(cNode, character) : null,
                 })
             }
 
@@ -120,7 +126,12 @@ export default createRule("no-useless-escape", {
                             if (!canUnwrapped(cNode, char)) {
                                 return
                             }
-                            report(cNode, 0, char)
+                            report(
+                                cNode,
+                                0,
+                                char,
+                                !POTENTIAL_ESCAPE_SEQUENCE.has(char),
+                            )
                         }
                     }
                 },

tests/lib/rules/no-useless-escape.ts

@@ -69,6 +69,7 @@ tester.run("no-useless-escape", rule as any, {
     invalid: [
         {
             code: String.raw`/\a/`,
+            output: String.raw`/a/`,
             errors: [
                 {
                     message: "Unnecessary escape character: \\a.",
@@ -81,18 +82,22 @@ tester.run("no-useless-escape", rule as any, {
         },
         {
             code: `/\\x7/`,
+            output: null,
             errors: ["Unnecessary escape character: \\x."],
         },
         {
             code: `/\\u41/`,
+            output: null,
             errors: ["Unnecessary escape character: \\u."],
         },
         {
             code: `/\\u{[41]}/`,
+            output: null,
             errors: ["Unnecessary escape character: \\u."],
         },
         {
             code: String.raw`/[ \^ \/ \. \$ \* \+ \? \[ \{ \} \| \( \) \k<title> \B \8 \9]/`,
+            output: String.raw`/[ ^ / . $ * + ? [ { } | ( ) \k<title> B 8 9]/`,
             errors: [
                 "Unnecessary escape character: \\^.",
                 "Unnecessary escape character: \\/.",
@@ -115,6 +120,7 @@ tester.run("no-useless-escape", rule as any, {
         },
         {
             code: String.raw`/\p{ASCII}/; /[\p{ASCII}]/; /\P{ASCII}/; /[\P{ASCII}]/`, // Missing u flag
+            output: null,
             errors: [
                 "Unnecessary escape character: \\p.",
                 "Unnecessary escape character: \\p.",