eslint.config.js

// Flat ESLint config for the jsonforms-lit workspace.
import js from '@eslint/js';
import tsparser from '@typescript-eslint/parser';
import tsplugin from '@typescript-eslint/eslint-plugin';
import prettier from 'eslint-config-prettier';

export default [
  // Global ignores — must be in its own config entry with no other keys.
  {
    ignores: [
      '**/dist/**',
      '**/node_modules/**',
      '**/*.tsbuildinfo',
      '**/coverage/**',
      'apps/demo/dist/**',
      'pnpm-lock.yaml',
    ],
  },
  js.configs.recommended,
  {
    files: ['**/*.ts'],
    languageOptions: {
      parser: tsparser,
      parserOptions: {
        ecmaVersion: 2022,
        sourceType: 'module',
        // Type-aware linting. A dedicated `tsconfig.eslint.json` covers
        // every source + test file across the workspace without fighting
        // the per-package `rootDir` settings used by `tsc --build`.
        project: ['./tsconfig.eslint.json'],
        tsconfigRootDir: import.meta.dirname,
      },
      globals: {
        window: 'readonly',
        document: 'readonly',
        navigator: 'readonly',
        customElements: 'readonly',
        HTMLElement: 'readonly',
        HTMLInputElement: 'readonly',
        HTMLSelectElement: 'readonly',
        HTMLTextAreaElement: 'readonly',
        HTMLButtonElement: 'readonly',
        HTMLDivElement: 'readonly',
        HTMLLegendElement: 'readonly',
        HTMLLabelElement: 'readonly',
        HTMLOptionElement: 'readonly',
        ShadowRoot: 'readonly',
        DocumentFragment: 'readonly',
        ParentNode: 'readonly',
        Node: 'readonly',
        Element: 'readonly',
        Event: 'readonly',
        CustomEvent: 'readonly',
        KeyboardEvent: 'readonly',
        MouseEvent: 'readonly',
        InputEvent: 'readonly',
        PropertyKey: 'readonly',
        NodeFilter: 'readonly',
        MutationObserver: 'readonly',
        CSSStyleSheet: 'readonly',
        CustomElementConstructor: 'readonly',
        getComputedStyle: 'readonly',
        requestAnimationFrame: 'readonly',
        cancelAnimationFrame: 'readonly',
        console: 'readonly',
        setTimeout: 'readonly',
        clearTimeout: 'readonly',
        queueMicrotask: 'readonly',
        Symbol: 'readonly',
        Promise: 'readonly',
        process: 'readonly',
      },
    },
    plugins: {
      '@typescript-eslint': tsplugin,
    },
    rules: {
      // TS handles undefined symbols and unused imports; eslint's
      // no-undef / no-unused-vars don't understand type imports.
      'no-undef': 'off',
      'no-unused-vars': 'off',
      '@typescript-eslint/no-unused-vars': [
        'warn',
        {
          argsIgnorePattern: '^_',
          varsIgnorePattern: '^_',
          caughtErrorsIgnorePattern: '^_',
        },
      ],
      'no-empty': ['error', { allowEmptyCatch: true }],
      // Type-aware safety rules — catch forgotten awaits and promise
      // misuse in the Lit async update machinery.
      '@typescript-eslint/no-floating-promises': 'error',
      '@typescript-eslint/no-misused-promises': [
        'error',
        {
          checksVoidReturn: {
            // Event handlers legitimately return promises (async
            // `@click` handlers etc.) and that's fine in lit-html.
            attributes: false,
            arguments: false,
          },
        },
      ],
      // Prefer the `import type` form for type-only imports so output
      // code stays clean and `verbatimModuleSyntax` can be enabled later
      // without churn.
      '@typescript-eslint/consistent-type-imports': [
        'warn',
        {
          prefer: 'type-imports',
          disallowTypeAnnotations: false,
          fixStyle: 'separate-type-imports',
        },
      ],
    },
  },
  {
    // `describe` / `it` / `before` from `node:test` return promises that
    // the runner tracks internally; user code doesn't (and shouldn't) await
    // them. Same story for the `fixture.updateComplete` no-op awaits scattered
    // through integration tests. Turn off no-floating-promises inside tests
    // so the type-aware rule doesn't drown the genuine signal from src.
    files: ['**/test/**/*.ts'],
    rules: {
      '@typescript-eslint/no-floating-promises': 'off',
      '@typescript-eslint/no-misused-promises': 'off',
    },
  },
  {
    files: ['**/*.js', '**/*.mjs', '**/*.cjs'],
    languageOptions: {
      ecmaVersion: 2022,
      sourceType: 'module',
      globals: {
        console: 'readonly',
        process: 'readonly',
      },
    },
    rules: {
      'no-empty': ['error', { allowEmptyCatch: true }],
    },
  },
  prettier,
];