eslint 9 update

.editorconfig

@@ -6,3 +6,10 @@ indent_size = 4
 end_of_line = lf
 charset = utf-8
 insert_final_newline = true
+trim_trailing_whitespace = true
+
+[*.yml]
+indent_size = 2
+
+[*.json]
+indent_size = 2

.nvmrc

@@ -1 +1 @@
-18
+20

.vscode/settings.json

@@ -1,24 +1,26 @@
 {
-    "typescript.tsdk": "./node_modules/typescript/lib",
-    "typescript.enablePromptUseWorkspaceTsdk": true,
-    "langium.build.ignorePatterns": "node_modules,out,/packages/generator-langium/**",
-    "editor.guides.bracketPairs": true,
-    "eslint.codeAction.showDocumentation": {
-        "enable": true
-    },
-    "eslint.format.enable": true,
-    "eslint.validate": [
-        "javascript",
-        "typescript"
-    ],
-    "vitest.configSearchPatternExclude": "{**/node_modules/**,**/dist/**,**/generated/**,**/templates/**,**/examples/hello*/**,**/.*/**,**/*.d.ts}",
-    "vitest.debugExclude": [
-        "<node_internals>/**", "**/node_modules/**", "!**/node_modules/vscode-uri/**"
-    ],
-    "[json]": {
-        "editor.defaultFormatter": "vscode.json-language-features"
-    },
-    "[jsonc]": {
-        "editor.defaultFormatter": "vscode.json-language-features"
-    }
+  "typescript.tsdk": "./node_modules/typescript/lib",
+  "typescript.enablePromptUseWorkspaceTsdk": true,
+  "langium.build.ignorePatterns": "node_modules,out,/packages/generator-langium/**",
+  "editor.guides.bracketPairs": true,
+  "eslint.codeAction.showDocumentation": {
+    "enable": true
+  },
+  "eslint.format.enable": true,
+  "eslint.validate": [
+    "javascript",
+    "typescript"
+  ],
+  "vitest.configSearchPatternExclude": "{**/node_modules/**,**/dist/**,**/generated/**,**/templates/**,**/examples/hello*/**,**/.*/**,**/*.d.ts}",
+  "vitest.debugExclude": [
+    "<node_internals>/**",
+    "**/node_modules/**",
+    "!**/node_modules/vscode-uri/**"
+  ],
+  "[json]": {
+    "editor.defaultFormatter": "vscode.json-language-features"
+  },
+  "[jsonc]": {
+    "editor.defaultFormatter": "vscode.json-language-features"
+  }
 }

eslint.config.mjs

@@ -0,0 +1,204 @@
+import js from '@eslint/js';
+import globals from 'globals';
+import { FlatCompat } from '@eslint/eslintrc';
+import tsParser from '@typescript-eslint/parser';
+
+import pluginTypescriptEslint from '@typescript-eslint/eslint-plugin';
+import pluginImport from 'eslint-plugin-import';
+import pluginUnusedImports from 'eslint-plugin-unused-imports';
+import pluginHeader from 'eslint-plugin-header';
+import pluginStylistic from '@stylistic/eslint-plugin';
+
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+
+const compat = new FlatCompat({
+    baseDirectory: __dirname,
+    recommendedConfig: js.configs.recommended,
+    allConfig: js.configs.all
+});
+
+// Workaround, see https://github.com/Stuk/eslint-plugin-header/issues/57#issuecomment-2378485611
+pluginHeader.rules.header.meta.schema = false;
+
+export default [{
+    ignores: [
+        '**/node_modules/**/*',
+        '**/bin/**/*',
+        '**/bundle/**/*',
+        '**/dist/**/*',
+        '**/lib/**/*',
+        '**/out/**/*',
+        '**/resources/**/*',
+        '**/production/**/*',
+        '**/scripts/**/*',
+        '**/packages/generator-langium/app/**/*',
+        '**/packages/generator-langium/**/templates/**/*',
+        '**/*env.d.ts',
+        '**/esbuild.mjs',
+        // WA: 'no-useless-escape': 'off' has no effect
+        '**/examples/**/*.monarch.ts'
+    ],
+}, ...compat.extends('eslint:recommended', 'plugin:@typescript-eslint/recommended'), {
+    files: [
+        '**/src/**/*.ts',
+        '**/src/**/*.tsx',
+        '**/test/**/*.ts',
+        '**/test/**/*.tsx'
+    ],
+    plugins: {
+        '@typescript-eslint': pluginTypescriptEslint,
+        import: pluginImport,
+        'unused-imports': pluginUnusedImports,
+        pluginHeader,
+        '@stylistic': pluginStylistic
+    },
+    languageOptions: {
+        globals: {
+            ...globals.node,
+            ...globals.browser
+        },
+        parser: tsParser,
+        ecmaVersion: 2020,
+        sourceType: 'module',
+        parserOptions: {
+            project: ['./tsconfig.json']
+        }
+    },
+    // List of [ESLint rules](https://eslint.org/docs/rules/)
+    rules: {
+        // do not force arrow function parentheses
+        'arrow-parens': ['off', 'as-needed'],
+        // checks the correct use of super() in sub-classes
+        'constructor-super': 'error',
+        // obj.a instead of obj['a'] when possible
+        'dot-notation': 'error',
+        // ban '==', don't use 'smart' option!
+        eqeqeq: 'error',
+        // needs obj.hasOwnProperty(key) checks
+        'guard-for-in': 'error',
+        // new Error() instead of new Error
+        'new-parens': 'error',
+        // bitwise operators &, | can be confused with &&, ||
+        'no-bitwise': 'error',
+        // ECMAScript deprecated arguments.caller and arguments.callee
+        'no-caller': 'error',
+        // assignments if (a = '1') are error-prone
+        'no-cond-assign': 'error',
+        // disallow debugger; statements
+        'no-debugger': 'error',
+        // eval is considered unsafe
+        'no-eval': 'error',
+        // we need to have 'namespace' functions when using TS 'export ='
+        'no-inner-declarations': 'off',
+        // GOTO is only used in BASIC ;)
+        'no-labels': 'error',
+        // two or more empty lines need to be fused to one
+        'no-multiple-empty-lines': ['error', {
+            max: 1
+        }],
+        // there is no reason to wrap primitve values
+        'no-new-wrappers': 'error',
+        // only throw Error but no objects {}
+        'no-throw-literal': 'error',
+        // trim end of lines
+        'no-trailing-spaces': 'error',
+        // safe try/catch/finally behavior
+        'no-unsafe-finally': 'error',
+        // use const and let instead of var
+        'no-var': 'error',
+        // space in function decl: f() vs async () => {}
+        'space-before-function-paren': ['error', {
+            anonymous: 'never',
+            asyncArrow: 'always',
+            named: 'never'
+        }],
+        // Always use semicolons at end of statement
+        semi: [2, 'always'],
+        // Prefer single quotes
+        quotes: [2, 'single', {
+            avoidEscape: true
+        }],
+        // isNaN(i) Number.isNaN(i) instead of i === NaN
+        'use-isnan': 'error',
+        // Use MIT file header
+        'pluginHeader/header': [2, 'block', [
+            { pattern: 'MIT License|DO NOT EDIT MANUALLY!' }
+        ]],
+        'no-restricted-imports': ['error', {
+            paths: [{
+                name: 'vscode-jsonrpc',
+                importNames: [ 'CancellationToken' ],
+                message: 'Import "CancellationToken" via "Cancellation.CancellationToken" from "langium", or directly from "./utils/cancellation.ts" within Langium.'
+            }, {
+                name: 'vscode-jsonrpc/',
+                importNames: [ 'CancellationToken'],
+                message: 'Import "CancellationToken" via "Cancellation.CancellationToken" from "langium", or directly from "./utils/cancellation.ts" within Langium.'
+            }],
+            patterns: [ {
+                group: [ 'vscode-jsonrpc' ],
+                importNamePattern: '^(?!CancellationToken)',
+                message: 'Don\'t import types or symbols from "vscode-jsonrpc" (package index), as that brings a large overhead in bundle size. Import from "vscode-jsonrpc/lib/common/...js" and add a // eslint-disable..., if really necessary.'
+            }]
+        }],
+        // use @typescript-eslint/no-unused-vars instead
+        'no-unused-vars': 'off',
+        // Disallow unnecessary escape characters
+        'no-useless-escape': 'off',
+
+        // List of [@typescript-eslint rules](https://typescript-eslint.io/rules/)
+        // Require that function overload signatures be consecutive
+        '@typescript-eslint/adjacent-overload-signatures': 'error',
+        // Require consistently using either T[] or Array<T> for arrays
+        '@typescript-eslint/array-type': ['error', {
+            default: 'array-simple'
+        }],
+        // Disallow accidentally using the 'empty object' type
+        '@typescript-eslint/no-empty-object-type': 'error',
+        // Disallow explicit type declarations for variables or parameters initialized to a number, string, or boolean
+        '@typescript-eslint/no-inferrable-types': 'off',
+        // Disallow using the unsafe built-in Function type
+        '@typescript-eslint/no-unsafe-function-type': 'error',
+        // Disallow using confusing built-in primitive class wrappers
+        '@typescript-eslint/no-wrapper-object-types': 'error',
+        // Disallow the `any` type
+        '@typescript-eslint/no-explicit-any': 'error',
+        // Enforce valid definition of `new` and `constructor`
+        '@typescript-eslint/no-misused-new': 'error',
+        // Disallow TypeScript namespaces
+        '@typescript-eslint/no-namespace': 'off',
+        // Disallow non-null assertions using the ! postfix operator
+        '@typescript-eslint/no-non-null-assertion': 'off',
+        // Require or disallow parameter properties in class constructors
+        '@typescript-eslint/parameter-properties': 'off',
+        // Disallow unused variables
+        '@typescript-eslint/no-unused-vars': ['error', {
+            caughtErrorsIgnorePattern: '^_',
+            argsIgnorePattern: '^_',
+            varsIgnorePattern: '^_'
+        }],
+        // isallow require statements except in import statements
+        '@typescript-eslint/no-var-requires': 'error',
+        // Enforce the use of `for-of` loop over the standard `for` loop where possible
+        '@typescript-eslint/prefer-for-of': 'error',
+        // Require using `namespace` keyword over `module` keyword to declare custom TypeScript modules
+        '@typescript-eslint/prefer-namespace-keyword': 'error',
+        // Disallow certain triple slash directives in favor of ES6-style import declarations
+        '@typescript-eslint/triple-slash-reference': 'error',
+        // Disallow conditionals where the type is always truthy or always falsy
+        '@typescript-eslint/no-unnecessary-condition': 'off',
+        // Disallow unused expressions
+        '@typescript-eslint/no-unused-expressions': 'off',
+        // Enforce consistent usage of type imports
+        '@typescript-eslint/consistent-type-imports': 'error',
+
+        // List of [@stylistic rules](https://eslint.style/rules)
+        // Enforce consistent indentation
+        '@stylistic/indent': 'error',
+        // Require consistent spacing around type annotations
+        '@stylistic/type-annotation-spacing': 'error'
+    }
+}];