Add a legacy version of the configs for users who are not yet ready t…

…o move to eslint v9

.changeset/odd-seahorses-wait.md

@@ -0,0 +1,5 @@
+---
+'@putstack/eslint-config-typescript': minor
+---
+
+Add a legacy version of the configs for users who are not yet ready to move to eslint v9

packages/eslint-config-typescript/package.json

@@ -46,7 +46,7 @@
     "@types/eslint__js": "8.42.3"
   },
   "peerDependencies": {
-    "eslint": "^9.7.0",
+    "eslint": "^8.57.0 || ^9.7.0",
     "typescript": "^5"
   },
   "scripts": {

packages/eslint-config-typescript/src/index.ts

@@ -1,13 +1,22 @@
 import type { TSESLint } from '@typescript-eslint/utils';
 import { base } from './base';
+import { baseLegacyConfig } from './legacy-base';
 import { recommended } from './recommended';
 
 type ConfigTypes = 'base' | 'recommended';
+type LegacyConfigTypes = 'legacy/base' | 'legacy/recommended';
 
-const configs: Record<ConfigTypes, TSESLint.FlatConfig.ConfigArray> = {
+const flatConfigs: Record<ConfigTypes, TSESLint.FlatConfig.ConfigArray> = {
   base,
   recommended,
 };
 
+const legacyConfigs: Record<LegacyConfigTypes, TSESLint.ClassicConfig.Config> = {
+  'legacy/base': baseLegacyConfig,
+  'legacy/recommended': baseLegacyConfig,
+};
+
+const configs = { ...flatConfigs, ...legacyConfigs };
+
 export { configs };
 export default { configs };

packages/eslint-config-typescript/src/legacy-base.ts

@@ -0,0 +1,88 @@
+import type { TSESLint } from '@typescript-eslint/utils';
+
+export const baseLegacyConfig: TSESLint.ClassicConfig.Config = {
+  extends: [
+    //General eslint recommended rules
+    'eslint:recommended',
+    //General typescript-eslint rules that have type knowledge
+    'plugin:@typescript-eslint/recommended-type-checked',
+    'plugin:@typescript-eslint/stylistic-type-checked',
+    //General code quality rules
+    'plugin:sonarjs/recommended',
+    //General sorting rules (imports)
+    'plugin:perfectionist/recommended-alphabetical-legacy',
+    //General dependency rules to avoid tree bloat and redundant polyfills
+    'plugin:depend/recommended',
+  ],
+  parser: '@typescript-eslint/parser',
+  plugins: ['@typescript-eslint', 'perfectionist', 'sonarjs', 'depend'],
+  rules: {
+    /** ESLint plugin configuration */
+    /** Stylistic rules */
+    //Prefer using Array<T> over T[]
+    '@typescript-eslint/array-type': ['warn', { default: 'generic', readonly: 'generic' }],
+    //We want to encourage marking type imports explicitly which is also enforced by TypeScripts --verbatimModuleSyntax
+    '@typescript-eslint/consistent-type-imports': 'warn',
+    //We want to encourage marking type exports explicitly
+    '@typescript-eslint/consistent-type-exports': 'warn',
+    //Enforce the use of top-level import type qualifer when an import only has specifiers with inline type qualifiers
+    '@typescript-eslint/no-import-type-side-effects': 'warn',
+
+    /** Code quality rules */
+    //Enforce default clauses in switch statements to be last
+    'default-case-last': 'warn',
+    //Disallow nested ternary expressions
+    'no-nested-ternary': 'warn',
+    //Prefer the arrow callback of ES6 where possible
+    'prefer-arrow-callback': 'warn',
+
+    /** Rules that need to be turned off in default eslint to be turned on in Typescript ESLint */
+    //Enforce default parameters to be last
+    '@typescript-eslint/default-param-last': 'warn',
+    'default-param-last': 'off',
+    //Disallow variable declarations from shadowing variables declared in the outer scope
+    '@typescript-eslint/no-shadow': 'warn',
+    'no-shadow': 'off',
+    //Disallow variable redeclaration
+    '@typescript-eslint/no-redeclare': 'warn',
+    'no-redeclare': 'off',
+
+    //Emulate the TypeScript style of exempting names starting with _
+    '@typescript-eslint/no-unused-vars': [
+      'error',
+      {
+        args: 'all',
+        argsIgnorePattern: '^_',
+        caughtErrors: 'all',
+        caughtErrorsIgnorePattern: '^_',
+        destructuredArrayIgnorePattern: '^_',
+        ignoreRestSiblings: true,
+        varsIgnorePattern: '^_',
+      },
+    ],
+
+    //Set up a specific import order that we generally want to adhere to.
+    //This makes it easier to recognize where an import is coming from.
+    'perfectionist/sort-imports': [
+      'warn',
+      {
+        groups: ['builtin', 'external', 'internal', 'parent', 'sibling', 'index', 'object', 'unknown'],
+        ignoreCase: true,
+        newlinesBetween: 'never',
+        order: 'asc',
+        type: 'alphabetical',
+      },
+    ],
+    //If we have a list of objects, we want to sort them alphabetically, but we want to partition them by comments
+    'perfectionist/sort-objects': [
+      'error',
+      {
+        partitionByComment: true,
+      },
+    ],
+    //Turning this rule off as recommended in the perfectionist documention as it is handled by perfectionist in the following rules:
+    //sort-interfaces: https://eslint-plugin-perfectionist.azat.io/rules/sort-interfaces
+    //sort-objects: https://eslint-plugin-perfectionist.azat.io/rules/sort-object-types
+    '@typescript-eslint/adjacent-overload-signatures': 'off',
+  },
+};

packages/eslint-config-typescript/src/legacy-recommended.ts

@@ -0,0 +1,7 @@
+import type { TSESLint } from '@typescript-eslint/utils';
+import { baseLegacyConfig } from './legacy-base';
+
+export const recommendedLegacyConfig: TSESLint.ClassicConfig.Config = {
+  ...baseLegacyConfig,
+  extends: [...(baseLegacyConfig.extends as Array<string>), 'plugin:unicorn/recommended'],
+};