Migrate to ESLint v9 with strict rules (#39)

* Update keywords

* Seems like we are getting somewhere

* This is hard

* Update configs

* Replace app lint with default next strict

* Getting there

* Web is linting

* Make it work finally

* Clean up

* Use types over interfaces

apps/web/eslint.config.js

@@ -0,0 +1,34 @@
+// @ts-check
+/* eslint-disable */
+import { FlatCompat } from "@eslint/eslintrc";
+import baseConfig from "@repo/eslint-config/base";
+import tseslint from "typescript-eslint";
+
+const compat = new FlatCompat({
+  baseDirectory: import.meta.dirname,
+});
+
+export default tseslint.config(
+  ...baseConfig,
+  ...compat.config({
+    extends: ["next"],
+    settings: {
+      next: {
+        rootDir: "apps/web/", // required for monorepos
+      },
+    },
+  }),
+  tseslint.configs.strictTypeChecked,
+  tseslint.configs.stylisticTypeChecked,
+  {
+    languageOptions: {
+      parserOptions: {
+        projectService: true,
+        tsconfigRootDir: import.meta.dirname,
+      },
+    },
+    rules: {
+      "@typescript-eslint/use-unknown-in-catch-callback-variable": "off",
+    },
+  }
+);

apps/web/package.json

@@ -18,26 +18,25 @@
     "@typed-firestore/react": "1.0.0-0",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
-    "firebase": "^11.1.0",
-    "lucide-react": "^0.471.0",
-    "next": "15.1.4",
-    "react": "19.0.0",
-    "react-dom": "19.0.0",
+    "firebase": "^11.2.0",
+    "lucide-react": "^0.473.0",
+    "next": "^15.1.5",
+    "react": "^19.0.0",
+    "react-dom": "^19.0.0",
     "tailwind-merge": "^2.6.0",
     "tailwindcss-animate": "^1.0.7",
     "typescript": "^5.7.3"
   },
   "devDependencies": {
     "@codecompose/typescript-config": "^1.2.0",
     "@repo/eslint-config": "workspace:*",
-    "@types/node": "^22.10.5",
-    "@types/react": "^19.0.6",
+    "@types/node": "^22.10.7",
+    "@types/react": "^19.0.7",
     "@types/react-dom": "^19.0.3",
     "autoprefixer": "^10.4.20",
     "del-cli": "^6.0.0",
-    "eslint": "8.57.0",
-    "eslint-config-next": "15.1.4",
-    "postcss": "^8.4.49",
+    "eslint-config-next": "^15.1.5",
+    "postcss": "^8.5.1",
     "tailwindcss": "^3.4.17"
   }
 }

apps/web/src/app/components/counter-view.tsx

@@ -22,6 +22,8 @@ export function CounterView(props: { counterId: string }) {
       />
     );
   } else {
-    return <div>No counter document available. Please press "reset".</div>;
+    return (
+      <div>No counter document available. Please press &quot;reset&quot;.</div>
+    );
   }
 }

apps/web/src/app/components/key-value-list.tsx

@@ -7,7 +7,7 @@ type FsValue = string | number | boolean | null | FsTimestamp;
 
 export default function KeyValueList(props: {
   data: Record<string, FsValue>;
-  labels: Array<[string, string]>;
+  labels: [string, string][];
 }) {
   const rows = props.labels.map(([key, label]) => (
     <TableRow className="bg-white" key={key}>

apps/web/src/lib/api.ts

@@ -1,4 +1,5 @@
-const endpoint = process.env.NEXT_PUBLIC_DEMO_API_ENDPOINT;
+const endpoint =
+  process.env.NEXT_PUBLIC_DEMO_API_ENDPOINT ?? "__missing_demo_api_endpoint";
 
 /**
  * In a real application you would typically not embed an API key like this, as

apps/web/src/lib/utils/fetch.ts

@@ -1,6 +1,6 @@
 export async function fetchJson<T>(
   endpoint: string,
-  queryParams: { [key: string]: string | number | boolean | undefined } = {},
+  queryParams: Record<string, string | number | boolean | undefined> = {},
   options: RequestInit = {}
 ) {
   const queryString = makeQueryString(queryParams);
@@ -17,27 +17,29 @@ export async function fetchJson<T>(
 
   if (!response.ok) {
     throw new Error(
-      `Fetch to ${url} failed with status ${
+      `Fetch to ${url} failed with status ${String(
         response.status
-      }. Response text: ${await response.text()}`
+      )}. Response text: ${await response.text()}`
     );
   }
 
   try {
-    return response.json() as Promise<T>;
-  } catch (err) {
+    return (await response.json()) as T;
+  } catch {
     throw new Error(`Failed to parse JSON from response of ${url}`);
   }
 }
 
 function makeQueryString(
-  params: { [key: string]: string | number | boolean | undefined } = {}
+  params: Record<string, string | number | boolean | undefined> = {}
 ) {
   const queryString = new URLSearchParams();
 
   Object.entries(params)
     .filter(([, value]) => value !== undefined)
-    .forEach(([name, value]) => queryString.append(name, String(value)));
+    .forEach(([name, value]) => {
+      queryString.append(name, String(value));
+    });
 
   return queryString.toString();
 }

apps/web/tsconfig.json

@@ -1,6 +1,19 @@
 {
   "extends": "@codecompose/typescript-config/nextjs.json",
-  "include": ["src", ".next/types/**/*.ts"],
+  "compilerOptions": {
+    "plugins": [
+      {
+        "name": "next" // plugin comes installed with nextjs
+      }
+    ]
+  },
+  "include": [
+    "${configDir}",
+    "${configDir}/**/*.json",
+    "${configDir}/next-env.d.ts",
+    "${configDir}/.next/types/**/*.ts",
+    ".next/types/**/*.ts"
+  ],
   "references": [
     {
       "path": "../../packages/common"

apps/web/vendor.d.ts

@@ -0,0 +1 @@
+declare module "@eslint/eslintrc";

package.json

@@ -6,9 +6,10 @@
     "typescript",
     "monorepo",
     "firebase",
+    "firestore",
     "isolate-package",
+    "typed-firestore",
     "esm",
-    "turbo",
     "turborepo",
     "nextjs"
   ],
@@ -47,7 +48,7 @@
     "prettier-plugin-jsdoc": "^1.3.2",
     "turbo": "^2.3.3",
     "typescript": "^5.7.3",
-    "vercel": "^39.2.6",
-    "vitest": "^2.1.8"
+    "vercel": "^39.3.0",
+    "vitest": "^3.0.2"
   }
 }

packages/common/eslint.config.js

@@ -0,0 +1,15 @@
+// @ts-check
+import base from "@repo/eslint-config/base";
+import tseslint from "typescript-eslint";
+
+export default tseslint.config([
+  ...base,
+  {
+    languageOptions: {
+      parserOptions: {
+        tsconfigRootDir: import.meta.dirname,
+        allowDefaultProject: true,
+      },
+    },
+  },
+]);

packages/common/package.json

@@ -13,24 +13,26 @@
   "scripts": {
     "compile": "tsc --noEmit",
     "test": "vitest",
-    "lint": "eslint . --max-warnings 0",
     "build": "tsup && tsc --emitDeclarationOnly",
     "clean": "del-cli dist tsconfig.tsbuildinfo",
-    "coverage": "vitest run --coverage "
+    "lint": "eslint src --flag unstable_config_lookup_from_file --max-warnings 0",
+    "coverage": "vitest run --coverage"
   },
   "license": "MIT",
   "dependencies": {
-    "firebase": "^11.1.0",
-    "remeda": "^2.19.0"
+    "firebase": "^11.2.0",
+    "remeda": "^2.19.2"
   },
   "devDependencies": {
     "@codecompose/typescript-config": "^1.2.0",
+    "@eslint/js": "^9.18.0",
     "@repo/eslint-config": "workspace:*",
-    "eslint": "^8.57.1",
-    "eslint-plugin-require-extensions": "^0.1.3",
+    "del-cli": "^6.0.0",
+    "eslint": "^9.18.0",
     "prettier": "^3.4.2",
     "tsup": "^8.3.5",
     "typescript": "^5.7.3",
-    "vitest": "^2.1.8"
+    "typescript-eslint": "^8.20.0",
+    "vitest": "^3.0.2"
   }
 }

packages/common/src/utils/is-present.ts

@@ -1,5 +1,4 @@
-/** Copied from ts-is-present */
-export function isPresent<T>(t: T | undefined | null | void): t is T {
+export function isPresent<T>(t: T | undefined | null): t is T {
   return t !== undefined && t !== null;
 }
 

packages/core/eslint.config.js

@@ -0,0 +1,17 @@
+// @ts-check
+import baseConfig from "@repo/eslint-config/base";
+import tseslint from "typescript-eslint";
+
+export default tseslint.config([
+  ...baseConfig,
+  {
+    languageOptions: {
+      parserOptions: {
+        projectService: {
+          allowDefaultProject: ["*.js"],
+        },
+        tsconfigRootDir: import.meta.dirname,
+      },
+    },
+  },
+]);

packages/core/package.json

@@ -14,7 +14,7 @@
   },
   "scripts": {
     "compile": "tsc --noEmit",
-    "lint": "eslint . --max-warnings 0",
+    "lint": "eslint src --flag unstable_config_lookup_from_file --max-warnings 0 ",
     "test": "vitest",
     "build": "tsup && tsc --emitDeclarationOnly && tsc-alias --verbose",
     "clean": "del-cli dist tsconfig.tsbuildinfo",
@@ -25,18 +25,21 @@
     "@repo/common": "workspace:*",
     "@sindresorhus/is": "^7.0.1",
     "firebase-admin": "^13.0.2",
-    "firebase-functions": "^6.2.0"
+    "firebase-functions": "^6.2.0",
+    "get-or-throw": "^1.4.0"
   },
   "devDependencies": {
     "@codecompose/typescript-config": "^1.2.0",
+    "@eslint/js": "^9.18.0",
     "@repo/eslint-config": "workspace:*",
-    "@types/node": "^22.10.5",
+    "@types/node": "^22.10.7",
     "del-cli": "^6.0.0",
-    "eslint": "^8.57.1",
+    "eslint": "^9.18.0",
     "npm-run-all": "^4.1.5",
     "tsc-alias": "^1.8.10",
     "tsup": "^8.3.5",
     "typescript": "^5.7.3",
-    "vitest": "^2.1.8"
+    "typescript-eslint": "^8.20.0",
+    "vitest": "^3.0.2"
   }
 }

packages/core/src/config.ts

@@ -1,5 +1,3 @@
-export const isProduction = false;
-
-export const region = isProduction ? "us-central1" : "europe-west3";
+export const region = "europe-west3";
 
 export const retryEventMaxAgeMs = 30000;