familysync/eslint.config.js

// eslint.config.js — root flat ESLint config (ESM)
// Covers: apps/api (Node/TS) + apps/pwa (React 19 + TypeScript)
// typescript-eslint v8, projectService: true (auto-discovers all tsconfigs)
// ESLint pinned to 9.39.4 — do NOT upgrade to ESLint 10 until eslint-plugin-react
// resolves the "getFilename is not a function" incompatibility (jsx-eslint#3977).

import js from '@eslint/js'
import tseslint from 'typescript-eslint'
import reactPlugin from 'eslint-plugin-react'
import reactHooks from 'eslint-plugin-react-hooks'
import prettierConfig from 'eslint-config-prettier/flat'

export default tseslint.config(
  // ── 1. Global ignores (replaces .eslintignore) ────────────────────────────
  {
    ignores: [
      '**/dist/**',           // build output: apps/api/dist, apps/pwa/dist, generated sw.js
      '**/node_modules/**',
      'apps/api/src/db/migrations/**', // generated Drizzle SQL files
      'pnpm-lock.yaml',
    ],
  },

  // ── 2. Base: all TS/TSX files in both apps ────────────────────────────────
  // Uses recommendedTypeChecked (type-aware) per D-13-01.
  // NOT strict/strictTypeChecked — D-13-03 explicitly rejects the extra churn.
  {
    files: ['apps/**/*.{ts,tsx}'],
    extends: [
      js.configs.recommended,
      tseslint.configs.recommendedTypeChecked,
    ],
    languageOptions: {
      parserOptions: {
        projectService: true,
        tsconfigRootDir: import.meta.dirname,
      },
    },
    rules: {
      // Allow _-prefixed names as intentionally unused (params + vars)
      '@typescript-eslint/no-unused-vars': [
        'error',
        { argsIgnorePattern: '^_', varsIgnorePattern: '^_' },
      ],
    },
  },

  // ── 3. React + Hooks: PWA only (D-13-02) ────────────────────────────────
  // Apps/api is Node/TS only — React config does NOT apply there.
  {
    files: ['apps/pwa/**/*.{ts,tsx}'],
    extends: [
      reactPlugin.configs.flat.recommended,
      reactHooks.configs.flat.recommended,
    ],
    settings: {
      react: { version: 'detect' },
    },
    rules: {
      // TypeScript props typing supersedes prop-types in React 19 (RESEARCH Open Question 2)
      'react/prop-types': 'off',
      // React 19 uses the automatic JSX transform (jsx: "react-jsx") — React does not
      // need to be in scope. The flat.recommended config enables this rule; we disable it.
      'react/react-in-jsx-scope': 'off',
      // react-hooks v7.1.1 flat.recommended enables React Compiler rules (immutability,
      // set-state-in-effect, purity, refs, etc.). These rules are designed for use with
      // the React Compiler and flag valid pre-Compiler React patterns as violations.
      // This codebase does NOT use the React Compiler — disable the Compiler-only rules.
      'react-hooks/set-state-in-effect': 'off',
      'react-hooks/immutability': 'off',
      'react-hooks/purity': 'off',
      'react-hooks/refs': 'off',
      'react-hooks/static-components': 'off',
      'react-hooks/use-memo': 'off',
      'react-hooks/preserve-manual-memoization': 'off',
      'react-hooks/incompatible-library': 'off',
      'react-hooks/globals': 'off',
      'react-hooks/error-boundaries': 'off',
      'react-hooks/set-state-in-render': 'off',
      'react-hooks/unsupported-syntax': 'off',
      'react-hooks/config': 'off',
      'react-hooks/gating': 'off',
      // exhaustive-deps fires as a warn in v7 flat recommended; with --max-warnings 0
      // that counts as a failure. Promote to error so violations are surfaced explicitly.
      'react-hooks/exhaustive-deps': 'error',
    },
  },

  // ── 4. disableTypeChecked override (D-13-10) ─────────────────────────────
  // These files are outside all tsconfig projects (tool configs + API test dir).
  // projectService: true cannot type-check them → disable type-aware rules only.
  // Non-type-aware rules (syntax, no-unused-vars) still apply.
  // Source: typescript-eslint.io/troubleshooting/typed-linting/#i-get-errors-telling-me-the-file-must-be-included
  {
    files: [
      'apps/api/drizzle.config.ts',
      'apps/api/vitest.config.ts',
      'apps/pwa/vite.config.ts',
      'apps/pwa/vitest.config.ts',
      'apps/pwa/playwright.config.ts',
      'apps/api/tests/**/*.ts', // excluded from apps/api/tsconfig.json (Pitfall 2)
      // e2e specs live in tsconfig.e2e.json which extends tsconfig.json; projectService
      // discovers tsconfigs by walking up from each file's directory, but the e2e dir
      // has no tsconfig of its own — projectService maps it to tsconfig.e2e.json only
      // when that tsconfig explicitly names the files. In practice projectService cannot
      // find these files via automatic discovery, so type-aware rules are disabled here.
      'apps/pwa/e2e/**/*.ts',
      'eslint.config.js',       // this file itself (not a ts project member)
    ],
    extends: [tseslint.configs.disableTypeChecked],
  },

  // ── 5. eslint-config-prettier: MUST BE LAST ──────────────────────────────
  // Disables all ESLint formatting rules that conflict with Prettier (D-13-07).
  // Use the /flat import path for ESM flat config (Pitfall 7).
  // Source: github.com/prettier/eslint-config-prettier
  prettierConfig,
)