feat: add support for eslint v9 (#673)

Author: ota-meshi

.changeset/stale-crews-brush.md

@@ -0,0 +1,5 @@
+---
+"eslint-plugin-svelte": patch
+---
+
+feat: add support for eslint v9

.eslintrc.js

@@ -94,7 +94,7 @@ module.exports = {
 					},
 					{
 						selector: 'variable',
-						format: ['camelCase', 'UPPER_CASE'],
+						format: ['camelCase', 'UPPER_CASE', 'PascalCase'],
 						leadingUnderscore: 'allow',
 						trailingUnderscore: 'allow'
 					},
@@ -156,7 +156,8 @@ module.exports = {
 		{
 			files: ['tests/**'],
 			rules: {
-				'@typescript-eslint/no-misused-promises': 'off'
+				'@typescript-eslint/no-misused-promises': 'off',
+				'@typescript-eslint/no-require-imports': 'off'
 			}
 		},
 		{

.github/workflows/NodeCI.yml

@@ -41,6 +41,11 @@ jobs:
         os: [ubuntu-latest]
         eslint: [7, 8]
         node: [20]
+        include:
+          # On next ESLint version
+          - eslint: ^9.0.0-0
+            node: 20
+            os: ubuntu-latest
     steps:
       - name: Checkout
         uses: actions/checkout@v4

.vscode/settings.json

@@ -6,5 +6,6 @@
 		"source.fixAll": "explicit",
 		"source.fixAll.stylelint": "explicit"
 	},
-	"svelte.plugin.typescript.diagnostics.enable": false
+	"svelte.plugin.typescript.diagnostics.enable": false,
+	"typescript.tsdk": "node_modules/typescript/lib"
 }

package.json

@@ -57,7 +57,7 @@
     "version:ci": "env-cmd -e version-ci pnpm run update && changeset version"
   },
   "peerDependencies": {
-    "eslint": "^7.0.0 || ^8.0.0-0",
+    "eslint": "^7.0.0 || ^8.0.0-0 || ^9.0.0-0",
     "svelte": "^3.37.0 || ^4.0.0 || ^5.0.0-next.33"
   },
   "peerDependenciesMeta": {
@@ -69,7 +69,7 @@
     "@eslint-community/eslint-utils": "^4.2.0",
     "@jridgewell/sourcemap-codec": "^1.4.14",
     "debug": "^4.3.1",
-    "eslint-compat-utils": "^0.4.0",
+    "eslint-compat-utils": "^0.4.1",
     "esutils": "^2.0.3",
     "known-css-properties": "^0.29.0",
     "postcss": "^8.4.5",

src/rules/no-spaces-around-equal-signs-in-attribute.ts

@@ -9,7 +9,7 @@ export default createRule('no-spaces-around-equal-signs-in-attribute', {
 			recommended: false,
 			conflictWithPrettier: true
 		},
-		schema: {},
+		schema: [],
 		fixable: 'whitespace',
 		messages: {
 			noSpaces: 'Unexpected spaces found around equal signs.'

src/rules/prefer-destructured-store-props.ts

@@ -186,7 +186,7 @@ export default createRule('prefer-destructured-store-props', {
 						//  dynamic accesses like {$foo[bar]}
 						!node.computed
 					) {
-						for (const variable of findReactiveVariable(node.object, node.property.name)) {
+						for (const variable of new Set(findReactiveVariable(node.object, node.property.name))) {
 							suggest.push({
 								messageId: 'fixUseVariable',
 								data: {

src/utils/eslint-core.ts

@@ -76,11 +76,17 @@ let ruleMap: Map<string, RuleModule> | null = null;
  * Get the core rule implementation from the rule name
  */
 export function getCoreRule(ruleName: string): RuleModule {
-	let map: Map<string, RuleModule>;
-	if (ruleMap) {
-		map = ruleMap;
-	} else {
-		ruleMap = map = (new Linter() as any).getRules();
+	try {
+		const map: Map<string, RuleModule> = ruleMap
+			? ruleMap
+			: (ruleMap = (new Linter() as any).getRules());
+		return map.get(ruleName)!;
+	} catch {
+		// getRules() is no longer available in flat config.
 	}
-	return map.get(ruleName)!;
+
+	// eslint-disable-next-line @typescript-eslint/no-require-imports , @typescript-eslint/no-var-requires -- Ignore
+	const { builtinRules } = require('eslint/use-at-your-own-risk');
+	ruleMap = builtinRules;
+	return builtinRules.get(ruleName) || null;
 }

tests/fixtures/rules/no-inner-declarations/invalid/.eslintrc.json

@@ -0,0 +1,5 @@
+{
+	"rules": {
+		"no-var": "off"
+	}
+}

tests/fixtures/rules/no-inner-declarations/invalid/_config.json

@@ -0,0 +1,3 @@
+{
+	"options": ["functions", { "blockScopedFunctions": "disallow" }]
+}