[PET-40] Replace eslint and prettier with biome (Migrate to Biome and standardize TypeScript imports)

.zed/settings.json

@@ -0,0 +1,40 @@
+{
+  "language_servers": ["!eslint", "..."],
+  "code_actions_on_format": {
+    "source.action.useSortedAttributes.biome": true,
+    "source.action.useSortedKeys.biome": true,
+    "source.fixAll.biome": true,
+  },
+  "languages": {
+    "JavaScript": {
+      "formatter": {
+        "language_server": { "name": "biome" },
+      },
+    },
+    "TypeScript": {
+      "formatter": {
+        "language_server": { "name": "biome" },
+      },
+    },
+    "TSX": {
+      "formatter": {
+        "language_server": { "name": "biome" },
+      },
+    },
+    "JSON": {
+      "formatter": {
+        "language_server": { "name": "biome" },
+      },
+    },
+    "CSS": {
+      "formatter": {
+        "language_server": { "name": "biome" },
+      },
+    },
+    "YAML": {
+      "formatter": {
+        "language_server": { "name": "biome" },
+      },
+    },
+  },
+}

CLAUDE.md

@@ -11,9 +11,9 @@ Petka is a Slovenian-language Wordle clone built with React Native / Expo. The b
 ```bash
 pnpm install            # Install dependencies
 pnpm start              # Start Expo dev server
-pnpm run lint           # ESLint via expo lint
+pnpm run lint           # Biome check
 pnpm run typecheck      # tsc --noEmit
-pnpm run format         # Prettier --write .
+pnpm run format         # Biome format --write .
 pnpm test               # Jest
 pnpm test:coverage      # Jest with coverage
 pnpm test path/to/test.ts   # Single test file
@@ -58,17 +58,17 @@ Each resource (users, puzzles, leaderboards, etc.) has its own folder with:
 
 `convex/schema.ts` assembles all table definitions and their indexes. `convex/convex.config.ts` registers Convex components (crons, migrations, expo-push-notifications, presence). Never edit `convex/_generated/`.
 
-Validators use `zod` via `convex-helpers` (`zodToConvex`, `zid` for typed document IDs).
+Validators use `zod` (v4) via `convex-helpers/server/zod4` (`zodToConvex`, `zid` for typed document IDs).
 
 ## Code conventions
 
-**Imports:** ordered `object → builtin → external → internal → parent → sibling → index`, with a blank line between groups. Internal paths use the `@/` alias (maps to `src/`). Type-only imports must use `import { type X }` syntax.
+**Imports:** ordered `object → builtin → external → internal → parent → sibling → index`, with a blank line between groups. Internal paths use the `@/` alias (maps to `src/`). Type-only imports must use `import type { X }` syntax (also enforced by biome). For mixed imports use `import { Component, type ComponentProps }` syntax.
 
-**JSX props:** `key` and `ref` come first (enforced by ESLint), remaining props alphabetically.
+**JSX props:** all props sorted alphabetically (enforced by Biome `useSortedAttributes`).
 
 **Unused vars:** prefix with `_` to suppress the lint rule (`_unusedVar`). Avoid doing that unless absolutely necessary.
 
-**Prettier:** 120-char line width, single quotes, 2-space indent, trailing commas (ES5).
+**Biome:** 120-char line width, single quotes, 2-space indent, trailing commas (ES5). Config in `biome.json`.
 
 **Convex mutations:** always use `generateUseMutationHook` — it provides consistent loading state and PostHog error capture. Do not call `useMutation` directly in components.
 

babel.config.cjs

@@ -1,4 +1,4 @@
-module.exports = function (api) {
+module.exports = (api) => {
   api.cache(true);
 
   return {

biome.json

@@ -0,0 +1,31 @@
+{
+  "$schema": "https://biomejs.dev/schemas/2.4.8/schema.json",
+  "vcs": { "enabled": true, "clientKind": "git", "useIgnoreFile": true },
+  "files": { "includes": ["**", "!!**/dist", "!!convex/_generated", "!!.zed"] },
+  "formatter": {
+    "enabled": true,
+    "indentStyle": "space",
+    "indentWidth": 2,
+    "lineEnding": "lf",
+    "lineWidth": 120
+  },
+  "linter": {
+    "enabled": true,
+    "rules": {
+      "recommended": true,
+      "style": { "noNonNullAssertion": "off" },
+      "suspicious": { "noNonNullAssertedOptionalChain": "off" }
+    }
+  },
+  "javascript": {
+    "formatter": {
+      "quoteStyle": "single",
+      "trailingCommas": "es5",
+      "semicolons": "always"
+    }
+  },
+  "assist": {
+    "enabled": true,
+    "actions": { "source": { "organizeImports": "on", "useSortedAttributes": "on" } }
+  }
+}

convex/leaderboards/queries.ts

@@ -1,20 +1,20 @@
-import { type NamedTableInfo, type Query } from 'convex/server';
+import type { NamedTableInfo, Query } from 'convex/server';
 import { ConvexError } from 'convex/values';
 import { zid } from 'convex-helpers/server/zod4';
 import { z } from 'zod';
 
 import { internal } from '../_generated/api';
-import { type DataModel, type Id } from '../_generated/dataModel';
+import type { DataModel, Id } from '../_generated/dataModel';
 import { generateRandomString, weekBounds, windowAround } from '../shared/helpers';
 import { internalMutation, mutation, query } from '../shared/queries';
-import { type User } from '../users/models';
+import type { User } from '../users/models';
 
 import {
   createLeaderboardModel,
+  type LeaderboardWithScores,
   leaderboardRange,
   leaderboardType,
   updateLeaderboardModel,
-  type LeaderboardWithScores,
 } from './models';
 
 export const list = query({

convex/migrations.ts

@@ -1,7 +1,7 @@
 import { Migrations } from '@convex-dev/migrations';
 
 import { components, internal } from './_generated/api.js';
-import { type DataModel } from './_generated/dataModel.js';
+import type { DataModel } from './_generated/dataModel.js';
 
 export const migrations = new Migrations<DataModel>(components.migrations);
 export const run = migrations.runner();

convex/shared/queries.ts

@@ -1,11 +1,11 @@
 import { NoOp } from 'convex-helpers/server/customFunctions';
-import { zCustomQuery, zCustomAction, zCustomMutation } from 'convex-helpers/server/zod4';
+import { zCustomAction, zCustomMutation, zCustomQuery } from 'convex-helpers/server/zod4';
 
 import {
-  query as baseQuery,
   action as baseAction,
-  mutation as baseMutation,
   internalMutation as baseInternalMutation,
+  mutation as baseMutation,
+  query as baseQuery,
 } from '../_generated/server';
 
 export const query = zCustomQuery(baseQuery, NoOp);

db/seeders/dictionaryEntries/getDictionaryWords.js

@@ -1,9 +1,8 @@
-import fs, { readFile } from 'fs/promises';
-import { createWriteStream } from 'fs';
-import path from 'path';
+import { createWriteStream } from 'node:fs';
+import fs, { readFile } from 'node:fs/promises';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
 import * as cheerio from 'cheerio';
-
-import { fileURLToPath } from 'url';
 import { XMLParser } from 'fast-xml-parser';
 
 import { fetchDictionaryTermHtml } from './utils.js';
@@ -87,7 +86,7 @@ async function readAndParseXmlFiles(directoryPath) {
       const isValid = await isValidDictionaryTerm(item.word);
       if (isValid) {
         console.log(`Writing word: ${item.word} with frequency: ${item.frequency}`);
-        writeStream.write(JSON.stringify(item) + '\n');
+        writeStream.write(`${JSON.stringify(item)}\n`);
       } else {
         console.warn('Found illegal word: ', item.word);
       }

db/seeders/dictionaryEntries/getDictionaryWordsExplanations.js

@@ -1,7 +1,7 @@
-import fs from 'fs';
-import readline from 'readline';
-import path from 'path';
-import { fileURLToPath } from 'url';
+import fs from 'node:fs';
+import path from 'node:path';
+import readline from 'node:readline';
+import { fileURLToPath } from 'node:url';
 import * as cheerio from 'cheerio';
 
 import { fetchDictionaryTermHtml } from './utils.js';

jest.setup.tsx

@@ -1,6 +1,5 @@
-/* eslint-disable @typescript-eslint/no-require-imports */
-import { type Octicons } from '@expo/vector-icons';
-import { type ComponentProps } from 'react';
+import type { Octicons } from '@expo/vector-icons';
+import type { ComponentProps } from 'react';
 import { Text as MockText } from 'react-native';
 
 jest.mock('@react-native-async-storage/async-storage', () =>
@@ -19,6 +18,7 @@ jest.mock('expo', () => ({
 
 jest.mock('@expo/vector-icons', () => ({
   ...jest.requireActual('@expo/vector-icons'),
+  // biome-ignore lint/suspicious/noExplicitAny: Test mock, fine with any
   Octicons: (props: ComponentProps<typeof Octicons> & { uniProps?: (theme: unknown) => any }) => {
     const { defaultTheme } = jest.requireActual('./src/styles/themes');
     const transformedProps = props.uniProps ? props.uniProps(defaultTheme) : {};

package.json

@@ -8,16 +8,15 @@
     "android": "expo run:android",
     "ios": "expo run:ios",
     "web": "expo start --web",
-    "lint": "expo lint",
+    "lint": "biome check .",
     "typecheck": "tsc --noEmit",
-    "format": "prettier --write .",
+    "format": "biome format --write .",
     "prepare": "husky",
     "test": "jest",
     "test:coverage": "jest --coverage --silent"
   },
   "lint-staged": {
-    "*.{js,ts,tsx,jsx,json,css,md}": "prettier --write",
-    "*.{js,ts,tsx,jsx}": "eslint --fix"
+    "*.{js,ts,tsx,jsx,json}": "biome check --write --no-errors-on-unmatched"
   },
   "dependencies": {
     "@convex-dev/crons": "^0.2.0",
@@ -86,29 +85,18 @@
   },
   "devDependencies": {
     "@babel/core": "^7.28.3",
+    "@biomejs/biome": "2.4.8",
     "@sentry/cli": "^2.53.0",
     "@testing-library/react-native": "^13.3.3",
     "@types/jest": "^29.5.14",
     "@types/react": "~19.2.14",
-    "@typescript-eslint/eslint-plugin": "^8.57.1",
-    "@typescript-eslint/parser": "^8.57.1",
-    "@typescript-eslint/typescript-estree": "^8.57.1",
-    "@typescript-eslint/utils": "^8.57.1",
     "cheerio": "^1.2.0",
-    "eslint": "^9.39.4",
-    "eslint-config-expo": "~55.0.0",
-    "eslint-config-prettier": "^10.1.8",
-    "eslint-plugin-import-x": "^4.16.2",
-    "eslint-plugin-prettier": "^5.5.5",
-    "eslint-plugin-unused-imports": "^4.4.1",
     "fast-xml-parser": "^5.5.6",
     "husky": "^9.1.7",
     "jest": "~29.7.0",
     "jest-expo": "~55.0.10",
     "lint-staged": "^16.4.0",
     "metro-core": "^0.83.1",
-    "prettier": "^3.8.1",
-    "prettier-eslint": "^16.4.2",
     "react-native-svg-transformer": "^1.5.1",
     "ts-jest": "^29.4.6",
     "typescript": "~5.9.3"