Update to eslint v9, typescript-eslint v8

eslint.config.mjs

@@ -123,24 +123,15 @@ export default tseslint.config(
             "@typescript-eslint/no-var-requires": "off",
             "@typescript-eslint/no-empty-interface": "off",
             "@typescript-eslint/no-explicit-any": "off",
-            "@typescript-eslint/ban-types": [
-                "error",
-                {
-                    extendDefaults: true,
-                    types: {
-                        // This is theoretically good, but ts-eslint appears to mistake our declaration of Symbol for the global Symbol type.
-                        // See: https://github.com/typescript-eslint/typescript-eslint/issues/7306
-                        "Symbol": false,
-                        "{}": false, // {} is a totally useful and valid type.
-                    },
-                },
-            ],
+            "@typescript-eslint/no-empty-object-type": "off", // {} is a totally useful and valid type.
+            "@typescript-eslint/no-require-imports": "off",
             "@typescript-eslint/no-unused-vars": [
                 "warn",
                 {
                     // Ignore: (solely underscores | starting with exactly one underscore)
                     argsIgnorePattern: "^(_+$|_[^_])",
                     varsIgnorePattern: "^(_+$|_[^_])",
+                    // Not setting an ignore pattern for caught errors; those can always be safely removed.
                 },
             ],
             "@typescript-eslint/no-inferrable-types": "off",
@@ -239,7 +230,8 @@ export default tseslint.config(
             "@typescript-eslint/interface-name-prefix": "off",
             "@typescript-eslint/prefer-function-type": "off",
             "@typescript-eslint/unified-signatures": "off",
-            "@typescript-eslint/ban-types": "off",
+            "@typescript-eslint/no-unsafe-function-type": "off",
+            "@typescript-eslint/no-wrapper-object-types": "off",
             "@typescript-eslint/no-unused-vars": "off",
 
             // scripts/eslint/rules

package.json

@@ -42,7 +42,7 @@
         "@dprint/formatter": "^0.4.1",
         "@dprint/typescript": "0.91.6",
         "@esfx/canceltoken": "^1.0.0",
-        "@eslint/js": "^8.57.0",
+        "@eslint/js": "^9.9.0",
         "@octokit/rest": "^21.0.1",
         "@types/chai": "^4.3.17",
         "@types/diff": "^5.2.1",
@@ -52,34 +52,35 @@
         "@types/node": "latest",
         "@types/source-map-support": "^0.5.10",
         "@types/which": "^3.0.4",
-        "@typescript-eslint/utils": "^7.18.0",
-        "azure-devops-node-api": "^14.0.1",
+        "@typescript-eslint/rule-tester": "^8.1.0",
+        "@typescript-eslint/utils": "^8.1.0",
+        "azure-devops-node-api": "^14.0.2",
         "c8": "^10.1.2",
         "chai": "^4.5.0",
         "chalk": "^4.1.2",
         "chokidar": "^3.6.0",
         "diff": "^5.2.0",
         "dprint": "^0.47.2",
         "esbuild": "^0.23.0",
-        "eslint": "^8.57.0",
-        "eslint-formatter-autolinkable-stylish": "^1.3.0",
+        "eslint": "^9.9.0",
+        "eslint-formatter-autolinkable-stylish": "^1.4.0",
         "fast-xml-parser": "^4.4.1",
         "glob": "^10.4.5",
         "globals": "^15.9.0",
         "hereby": "^1.9.0",
         "jsonc-parser": "^3.3.1",
-        "knip": "^5.27.0",
+        "knip": "^5.27.2",
         "minimist": "^1.2.8",
-        "mocha": "^10.7.0",
+        "mocha": "^10.7.3",
         "mocha-fivemat-progress-reporter": "^0.1.0",
-        "monocart-coverage-reports": "^2.10.0",
+        "monocart-coverage-reports": "^2.10.2",
         "ms": "^2.1.3",
         "node-fetch": "^3.3.2",
-        "playwright": "^1.45.3",
+        "playwright": "^1.46.0",
         "source-map-support": "^0.5.21",
         "tslib": "^2.6.3",
         "typescript": "^5.5.4",
-        "typescript-eslint": "^7.18.0",
+        "typescript-eslint": "^8.1.0",
         "which": "^3.0.1"
     },
     "overrides": {

scripts/eslint/tests/argument-trivia.test.cjs

@@ -2,10 +2,11 @@ const { RuleTester } = require("./support/RuleTester.cjs");
 const rule = require("../rules/argument-trivia.cjs");
 
 const ruleTester = new RuleTester({
-    parserOptions: {
-        warnOnUnsupportedTypeScriptVersion: false,
+    languageOptions: {
+        parserOptions: {
+            warnOnUnsupportedTypeScriptVersion: false,
+        },
     },
-    parser: require.resolve("@typescript-eslint/parser"),
 });
 
 ruleTester.run("argument-trivia", rule, {

scripts/eslint/tests/debug-assert.test.cjs

@@ -2,10 +2,11 @@ const { RuleTester } = require("./support/RuleTester.cjs");
 const rule = require("../rules/debug-assert.cjs");
 
 const ruleTester = new RuleTester({
-    parserOptions: {
-        warnOnUnsupportedTypeScriptVersion: false,
+    languageOptions: {
+        parserOptions: {
+            warnOnUnsupportedTypeScriptVersion: false,
+        },
     },
-    parser: require.resolve("@typescript-eslint/parser"),
 });
 
 ruleTester.run("debug-assert", rule, {

scripts/eslint/tests/js-extensions.cjs

@@ -2,10 +2,11 @@ const { RuleTester } = require("./support/RuleTester.cjs");
 const rule = require("../rules/js-extensions.cjs");
 
 const ruleTester = new RuleTester({
-    parserOptions: {
-        warnOnUnsupportedTypeScriptVersion: false,
+    languageOptions: {
+        parserOptions: {
+            warnOnUnsupportedTypeScriptVersion: false,
+        },
     },
-    parser: require.resolve("@typescript-eslint/parser"),
 });
 
 ruleTester.run("js-extensions", rule, {

scripts/eslint/tests/no-in-operator.test.cjs

@@ -2,10 +2,11 @@ const { RuleTester } = require("./support/RuleTester.cjs");
 const rule = require("../rules/no-in-operator.cjs");
 
 const ruleTester = new RuleTester({
-    parserOptions: {
-        warnOnUnsupportedTypeScriptVersion: false,
+    languageOptions: {
+        parserOptions: {
+            warnOnUnsupportedTypeScriptVersion: false,
+        },
     },
-    parser: require.resolve("@typescript-eslint/parser"),
 });
 
 ruleTester.run("no-in-operator", rule, {

scripts/eslint/tests/no-keywords.test.cjs

@@ -2,10 +2,11 @@ const { RuleTester } = require("./support/RuleTester.cjs");
 const rule = require("../rules/no-keywords.cjs");
 
 const ruleTester = new RuleTester({
-    parserOptions: {
-        warnOnUnsupportedTypeScriptVersion: false,
+    languageOptions: {
+        parserOptions: {
+            warnOnUnsupportedTypeScriptVersion: false,
+        },
     },
-    parser: require.resolve("@typescript-eslint/parser"),
 });
 
 ruleTester.run("no-keywords", rule, {

scripts/eslint/tests/only-arrow-functions.test.cjs

@@ -2,10 +2,11 @@ const { RuleTester } = require("./support/RuleTester.cjs");
 const rule = require("../rules/only-arrow-functions.cjs");
 
 const ruleTester = new RuleTester({
-    parserOptions: {
-        warnOnUnsupportedTypeScriptVersion: false,
+    languageOptions: {
+        parserOptions: {
+            warnOnUnsupportedTypeScriptVersion: false,
+        },
     },
-    parser: require.resolve("@typescript-eslint/parser"),
 });
 
 ruleTester.run("only-arrow-functions", rule, {

scripts/eslint/tests/support/RuleTester.cjs

@@ -1,6 +1,9 @@
 const path = require("path");
-const { TSESLint } = require("@typescript-eslint/utils");
+const Mocha = require("mocha");
+const { RuleTester } = require("@typescript-eslint/rule-tester");
+
+RuleTester.afterAll = Mocha.after;
 
 module.exports.ROOT_DIR = path.join(process.cwd(), "scripts", "eslint", "tests", "fixtures");
 module.exports.FILENAME = path.join(module.exports.ROOT_DIR, "file.ts");
-module.exports.RuleTester = TSESLint.RuleTester;
+module.exports.RuleTester = RuleTester;

scripts/failed-tests.cjs

@@ -45,7 +45,7 @@ class FailedTestsReporter extends Mocha.reporters.Base {
                 try {
                     reporter = require(reporterOptions.reporter);
                 }
-                catch (_) {
+                catch {
                     reporter = require(path.resolve(process.cwd(), reporterOptions.reporter));
                 }
             }

scripts/find-unused-diganostic-messages.mjs

@@ -18,7 +18,7 @@ startOfDiags.split(EOL).forEach(line => {
         execSync(`grep -rnw 'src' -e 'Diagnostics.${diagName}'`).toString();
         process.stdout.write(".");
     }
-    catch (error) {
+    catch {
         missingNames.push(diagName);
         process.stdout.write("x");
     }

src/compiler/sys.ts

@@ -1792,7 +1792,7 @@ export let sys: System = (() => {
             try {
                 buffer = _fs.readFileSync(fileName);
             }
-            catch (e) {
+            catch {
                 return undefined;
             }
             let len = buffer.length;
@@ -1863,7 +1863,7 @@ export let sys: System = (() => {
                                 continue;
                             }
                         }
-                        catch (e) {
+                        catch {
                             continue;
                         }
                     }
@@ -1882,7 +1882,7 @@ export let sys: System = (() => {
                 directories.sort();
                 return { files, directories };
             }
-            catch (e) {
+            catch {
                 return emptyFileSystemEntries;
             }
         }
@@ -1911,7 +1911,7 @@ export let sys: System = (() => {
                         return false;
                 }
             }
-            catch (e) {
+            catch {
                 return false;
             }
             finally {
@@ -1952,7 +1952,7 @@ export let sys: System = (() => {
             try {
                 return statSync(path)?.mtime;
             }
-            catch (e) {
+            catch {
                 return undefined;
             }
             finally {
@@ -1964,7 +1964,7 @@ export let sys: System = (() => {
             try {
                 _fs.utimesSync(path, time, time);
             }
-            catch (e) {
+            catch {
                 return;
             }
         }
@@ -1973,7 +1973,7 @@ export let sys: System = (() => {
             try {
                 return _fs.unlinkSync(path);
             }
-            catch (e) {
+            catch {
                 return;
             }
         }

src/compiler/utilitiesPublic.ts

@@ -723,7 +723,7 @@ export function validateLocaleAndSetLanguage(
         try {
             fileContents = sys.readFile(filePath);
         }
-        catch (e) {
+        catch {
             if (errors) {
                 errors.push(createCompilerDiagnostic(Diagnostics.Unable_to_open_file_0, filePath));
             }

src/compiler/watchUtilities.ts

@@ -198,7 +198,7 @@ export function createCachedDirectoryStructureHost(host: DirectoryStructureHost,
         try {
             return createCachedFileSystemEntries(rootDir, rootDirPath);
         }
-        catch (_e) {
+        catch {
             // If there is exception to read directories, dont cache the result and direct the calls to host
             Debug.assert(!cachedReadDirectoryResult.has(ensureTrailingDirectorySeparator(rootDirPath)));
             return undefined;

src/harness/harnessUtils.ts

@@ -41,7 +41,7 @@ export function readTestFile(path: string) {
     try {
         content = Harness.IO.readFile(Harness.userSpecifiedRoot + path);
     }
-    catch (err) {
+    catch {
         return undefined;
     }
 

src/tsserver/nodeServer.ts

@@ -124,7 +124,7 @@ export function initializeNodeSystem(): StartInput {
                 try {
                     this.fd = fs.openSync(this.logFilename, "w");
                 }
-                catch (_) {
+                catch {
                     // swallow the error and keep logging disabled if file cannot be opened
                 }
             }
@@ -280,7 +280,7 @@ export function initializeNodeSystem(): StartInput {
         const factory = require("./cancellationToken.js");
         cancellationToken = factory(sys.args);
     }
-    catch (e) {
+    catch {
         cancellationToken = ts.server.nullCancellationToken;
     }
 

src/typingsInstaller/nodeTypingsInstaller.ts

@@ -28,7 +28,7 @@ class FileLog implements ts.server.typingsInstaller.Log {
         try {
             fs.appendFileSync(this.logFile, `[${ts.server.nowString()}] ${text}${sys.newLine}`);
         }
-        catch (e) {
+        catch {
             this.logFile = undefined;
         }
     };