Update to eslint v9 flat config and typescript v5 (#576)

* chore: update to eslint v9 flat config and typescript v5

* revert jest setup file

bin/eslint-doc-generator.ts

@@ -8,9 +8,11 @@ import { run } from '../lib/cli.js';
 import { generate } from '../lib/generator.js';
 
 // eslint-disable-next-line unicorn/prefer-top-level-await -- TODO: use top-level await once updating TypeScript target to ES2022 (when dropping Node 14 support).
-run(process.argv, (path, options) => generate(path, options)).catch((error) => {
-  if (error instanceof Error) {
-    console.error(error.message);
+run(process.argv, (path, options) => generate(path, options)).catch(
+  (error: unknown) => {
+    if (error instanceof Error) {
+      console.error(error.message);
+    }
+    process.exitCode = 1;
   }
-  process.exitCode = 1;
-});
+);

eslint.config.js

@@ -0,0 +1,175 @@
+// @ts-check
+
+import js from '@eslint/js';
+import eslintPluginN from 'eslint-plugin-n';
+import eslintPluginJest from 'eslint-plugin-jest';
+import eslintPluginUnicorn from 'eslint-plugin-unicorn';
+import eslintPluginPrettierRecommended from 'eslint-plugin-prettier/recommended'; // eslint-disable-line import/extensions -- false positive
+import * as eslintPluginImport from 'eslint-plugin-import';
+import tseslint from 'typescript-eslint';
+
+export default tseslint.config(
+  // Configs:
+  js.configs.recommended,
+  eslintPluginImport.flatConfigs
+    ? eslintPluginImport.flatConfigs.recommended // TODO: use typescript config
+    : {},
+  eslintPluginJest.configs['flat/recommended'],
+  eslintPluginN.configs['flat/recommended'],
+  eslintPluginPrettierRecommended,
+  eslintPluginUnicorn.configs['flat/recommended'],
+  ...tseslint.configs.strictTypeChecked,
+
+  // Individual rules:
+  {
+    rules: {
+      'n/no-missing-import': 'off', // bug with recognizing node: prefix https://github.com/mysticatea/eslint-plugin-node/issues/275
+
+      'prettier/prettier': [
+        'error',
+        {
+          singleQuote: true,
+          trailingComma: 'es5', // TODO: remove this and use default
+        },
+      ],
+
+      // unicorn rules:
+      'require-unicode-regexp': 'error',
+      'unicorn/expiring-todo-comments': 'off',
+      'unicorn/import-style': 'off',
+      'unicorn/no-anonymous-default-export': 'off',
+      'unicorn/no-array-reduce': 'off',
+      'unicorn/no-nested-ternary': 'off',
+      'unicorn/no-useless-undefined': 'off', // We use a lot of `return undefined` to satisfy the `consistent-return` rule.
+      'unicorn/prefer-at': 'off',
+      'unicorn/prefer-string-raw': 'off',
+      'unicorn/prefer-string-replace-all': 'off',
+      'unicorn/prevent-abbreviations': 'off',
+
+      // typescript-eslint rules:
+      '@typescript-eslint/no-unnecessary-condition': 'off', // Dozens of places where the rule's `meta` property needs optional chaining get flagged by this.
+      '@typescript-eslint/no-unused-vars': 'off',
+      '@typescript-eslint/prefer-readonly': 'error',
+      '@typescript-eslint/require-array-sort-compare': 'error',
+
+      // Optional eslint rules:
+      'array-callback-return': 'error',
+      'block-scoped-var': 'error',
+      complexity: 'error',
+      'consistent-return': 'error',
+      curly: 'error',
+      'default-case': 'error',
+      eqeqeq: 'error',
+      'func-style': ['error', 'declaration'],
+      'new-parens': 'error',
+      'no-async-promise-executor': 'error',
+      'no-eval': 'error',
+      'no-extend-native': 'error',
+      'no-extra-bind': 'error',
+      'no-implicit-coercion': 'error',
+      'no-implied-eval': 'error',
+      'no-lone-blocks': 'error',
+      'no-multiple-empty-lines': 'error',
+      'no-new-func': 'error',
+      'no-new-wrappers': 'error',
+      'no-octal-escape': 'error',
+      'no-param-reassign': ['error', { props: true }],
+      'no-return-assign': 'error',
+      'no-return-await': 'error',
+      'no-self-compare': 'error',
+      'no-sequences': 'error',
+      'no-shadow-restricted-names': 'error',
+      'no-template-curly-in-string': 'error',
+      'no-throw-literal': 'error',
+      'no-unused-expressions': [
+        'error',
+        { allowShortCircuit: true, allowTernary: true },
+      ],
+      'no-use-before-define': ['error', 'nofunc'],
+      'no-useless-call': 'error',
+      'no-useless-catch': 'error',
+      'no-useless-computed-key': 'error',
+      'no-useless-concat': 'error',
+      'no-useless-constructor': 'error',
+      'no-useless-escape': 'error',
+      'no-useless-rename': 'error',
+      'no-useless-return': 'error',
+      'no-var': 'error',
+      'no-void': 'error',
+      'no-with': 'error',
+      'object-shorthand': 'error',
+      'prefer-const': 'error',
+      'prefer-numeric-literals': 'error',
+      'prefer-promise-reject-errors': 'error',
+      'prefer-rest-params': 'error',
+      'prefer-spread': 'error',
+      'prefer-template': 'error',
+      quotes: [
+        'error',
+        'single', // Must match quote style enforced by prettier.
+        // Disallow unnecessary template literals.
+        { avoidEscape: true, allowTemplateLiterals: false },
+      ],
+      radix: 'error',
+      'require-atomic-updates': 'error',
+      'require-await': 'error',
+      'spaced-comment': ['error', 'always', { markers: ['*', '!'] }],
+      'sort-vars': 'error',
+      yoda: 'error',
+
+      // import rules:
+      'import/default': 'off',
+      'import/export': 'error',
+      'import/extensions': ['error', 'always'],
+      'import/first': 'error',
+      'import/named': 'error',
+      'import/namespace': 'off',
+      'import/newline-after-import': 'error',
+      'import/no-absolute-path': 'error',
+      'import/no-cycle': 'off',
+      'import/no-deprecated': 'off',
+      'import/no-duplicates': 'error',
+      'import/no-dynamic-require': 'error',
+      'import/no-mutable-exports': 'error',
+      'import/no-named-as-default': 'off',
+      'import/no-named-as-default-member': 'off',
+      'import/no-named-default': 'error',
+      'import/no-self-import': 'error',
+      'import/no-unassigned-import': 'error',
+      'import/no-unresolved': 'off',
+      'import/no-unused-modules': 'error',
+      'import/no-useless-path-segments': 'error',
+      'import/no-webpack-loader-syntax': 'error',
+    },
+
+    // typescript-eslint parser options:
+    languageOptions: {
+      parserOptions: {
+        projectService: true,
+        tsconfigRootDir: import.meta.dirname,
+      },
+    },
+
+    linterOptions: {
+      reportUnusedDisableDirectives: 'error',
+    },
+  },
+
+  // Disabling type-checking for JS files:
+  {
+    files: ['**/*.js', '**/*.cjs'],
+    extends: [tseslint.configs.disableTypeChecked],
+  },
+
+  // Ignore files:
+  {
+    ignores: [
+      // compiled output
+      'dist/**',
+
+      // test
+      'coverage/**',
+      'test/fixtures/**',
+    ],
+  }
+);

jest.config.cjs → jest.config.ts

@@ -1,11 +1,11 @@
+import type { Config } from 'jest';
 // https://kulshekhar.github.io/ts-jest/docs/guides/esm-support/
-const { createDefaultEsmPreset } = require('ts-jest')
+import { createDefaultEsmPreset } from 'ts-jest';
 
-const defaultEsmPreset = createDefaultEsmPreset()
+const defaultEsmPreset = createDefaultEsmPreset();
 
-/** @type {import('ts-jest').JestConfigWithTsJest} */
-
-const jestConfig = {
+// https://kulshekhar.github.io/ts-jest/docs/guides/esm-support/
+const config: Config = {
   testEnvironment: 'node',
   testMatch: ['<rootDir>/test/**/*-test.ts'],
   setupFiles: ['<rootDir>/test/jest.setup.cjs'],
@@ -32,4 +32,4 @@ const jestConfig = {
   },
 };
 
-module.exports = jestConfig;
+export default config;

lib/config-format.ts

@@ -4,7 +4,7 @@ export const CONFIG_FORMATS = [
   'prefix-name',
 ] as const;
 
-export type ConfigFormat = typeof CONFIG_FORMATS[number];
+export type ConfigFormat = (typeof CONFIG_FORMATS)[number];
 
 export function configNameToDisplay(
   configName: string,

lib/config-list.ts

@@ -63,7 +63,7 @@ function generateConfigListMarkdown(
               pluginPrefix
             )}\``,
             hasDescription ? description || '' : undefined,
-          ].filter((col) => col !== undefined) as string[];
+          ].filter((col) => col !== undefined);
         }),
     ]),
     { align: 'l' } // Left-align headers.

lib/generator.ts

@@ -50,15 +50,15 @@ function stringOrArrayToArrayWithFallback(
     stringOrArray instanceof Array // eslint-disable-line unicorn/no-instanceof-array -- using Array.isArray() loses type information about the array.
       ? stringOrArray
       : stringOrArray
-      ? [stringOrArray]
-      : [];
+        ? [stringOrArray]
+        : [];
   const csvStringItem = asArray.find((item) => item.includes(','));
   if (csvStringItem) {
     throw new Error(
       `Provide property as array, not a CSV string: ${csvStringItem}`
     );
   }
-  return asArray && asArray.length > 0 ? asArray : fallback;
+  return asArray.length > 0 ? asArray : fallback;
 }
 
 // eslint-disable-next-line complexity
@@ -144,7 +144,7 @@ export async function generate(path: string, options?: GenerateOptions) {
     })
     .filter(
       // Filter out deprecated rules from being checked, displayed, or updated if the option is set.
-      ([, rule]) => !ignoreDeprecatedRules || !rule.meta.deprecated
+      ([, rule]) => !ignoreDeprecatedRules || !rule.meta?.deprecated
     )
     .sort(([a], [b]) => a.toLowerCase().localeCompare(b.toLowerCase()));
 

lib/option-parsers.ts

@@ -24,7 +24,9 @@ export function parseConfigEmojiOptions(
   const configsWithDefaultEmojiRemoved: string[] = [];
   const configEmojis =
     configEmoji?.flatMap((configEmojiItem) => {
-      const [config, emoji, ...extra] = configEmojiItem;
+      const [config, emoji, ...extra] = configEmojiItem as
+        | typeof configEmojiItem
+        | [configName: string, emoji: string, extra: string[]];
 
       // Check for duplicate configs.
       if (configsSeen.has(config)) {

lib/package-json.ts

@@ -116,7 +116,7 @@ export async function getPathWithExactFileNameCasing(path: string) {
       return resolve(dir, dirent.name);
     }
   }
-  return undefined; // eslint-disable-line unicorn/no-useless-undefined
+  return undefined;
 }
 
 export async function getCurrentPackageVersion(): Promise<string> {

lib/plugin-configs.ts

@@ -32,7 +32,7 @@ export function getConfigsThatSetARule(
         )
       )
       // Filter out ignored configs.
-      .filter(([configName]) => !ignoreConfig?.includes(configName))
+      .filter(([configName]) => !ignoreConfig.includes(configName))
       .map(([configName]) => configName)
       .sort((a, b) => a.toLowerCase().localeCompare(b.toLowerCase()))
   );
@@ -97,7 +97,7 @@ export function findConfigEmoji(
       emoji = `![badge-${configName}][]`;
     } else {
       // No fallback.
-      return undefined; // eslint-disable-line unicorn/no-useless-undefined
+      return undefined;
     }
   }