feat: adds eslint 9 config

apps/playground/package.json

@@ -7,7 +7,8 @@
     "build": "next build",
     "start": "next start",
     "lint": "next lint --max-warnings 0",
-    "check-types": "tsc --noEmit"
+    "check-types": "tsc --noEmit",
+    "clean": "rimraf .turbo node_modules dist coverage"
   },
   "dependencies": {
     "lucide-react": "0.544.0",

package.json

@@ -8,15 +8,17 @@
     "format": "prettier --write \"**/*.{ts,tsx,md}\"",
     "check-types": "turbo run check-types",
     "test": "turbo run test --no-cache",
-    "test:coverage": "turbo run test:coverage --no-cache"
+    "test:coverage": "turbo run test:coverage --no-cache",
+    "clean": "turbo run clean && rimraf node_modules .turbo coverage out"
   },
   "devDependencies": {
     "prettier": "^3.6.2",
     "turbo": "^2.5.8",
-    "typescript": "5.9.3"
+    "typescript": "5.9.3",
+    "rimraf": "6.0.1"
   },
   "packageManager": "pnpm@10.18.0",
   "engines": {
-    "node": ">=18"
+    "node": ">=18.18.0"
   }
 }

packages/js/eslint.config.mjs

@@ -0,0 +1,96 @@
+import js from "@eslint/js";
+import tseslint from "typescript-eslint";
+import vitest from "@vitest/eslint-plugin";
+import eslintConfigPrettier from "eslint-config-prettier";
+import importPlugin from "eslint-plugin-import";
+import checkFilePlugin from "eslint-plugin-check-file";
+import prettierPlugin from "eslint-plugin-prettier";
+import { fileURLToPath } from "url";
+import { dirname } from "path";
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+
+/**
+ * A shared ESLint configuration for the repository.
+ *
+ * @type {import("eslint").Linter.Config[]}
+ * */
+export default [
+  // Ignore patterns
+  {
+    ignores: [
+      "node_modules/",
+      "dist/",
+      "coverage/",
+      "*.config.js",
+      "*.config.ts",
+      "*.config.mjs",
+      "*.d.ts",
+    ],
+  },
+
+  // Base ESLint recommended rules
+  js.configs.recommended,
+
+  // Prettier rules
+  eslintConfigPrettier,
+
+  // TypeScript ESLint recommended rules
+  ...tseslint.configs.recommendedTypeChecked,
+  ...tseslint.configs.stylisticTypeChecked,
+
+  // Main configuration
+  {
+    plugins: {
+      import: importPlugin,
+      "check-file": checkFilePlugin,
+      prettier: prettierPlugin,
+    },
+    languageOptions: {
+      parserOptions: {
+        projectService: true,
+        tsconfigRootDir: __dirname,
+      },
+    },
+    rules: {
+      // no unused vars errors out but not when we use _
+      "@typescript-eslint/no-unused-vars": [
+        "error",
+        {
+          argsIgnorePattern: "^_",
+          varsIgnorePattern: "^_",
+        },
+      ],
+
+      // Import hygiene
+      "import/no-duplicates": "error",
+      "import/newline-after-import": "warn",
+
+      "check-file/filename-naming-convention": [
+        "error",
+        { "**/*.{ts,tsx}": "KEBAB_CASE" },
+        { ignoreMiddleExtensions: true },
+      ],
+      "prettier/prettier": "error",
+    },
+  },
+
+  // Vitest test files configuration
+  {
+    files: ["**/*.{test,spec}.ts", "**/*.{test,spec}.tsx"],
+    plugins: {
+      vitest,
+    },
+    rules: {
+      "vitest/consistent-test-it": [
+        "error",
+        { fn: "test", withinDescribe: "test" },
+      ],
+    },
+    settings: {
+      vitest: {
+        typecheck: true,
+      },
+    },
+  },
+];

packages/js/package.json

@@ -35,16 +35,24 @@
     "build": "tsc && vite build",
     "build:dev": "tsc && vite build --mode dev",
     "go": "vite build --watch --mode dev",
-    "lint": "eslint . --ext .ts,.js,.tsx,.jsx",
-    "clean": "rimraf .turbo node_modules dist coverage",
+    "lint": "eslint .",
     "test": "vitest run",
-    "test:coverage": "vitest run --coverage"
+    "test:coverage": "vitest run --coverage",
+    "clean": "rimraf .turbo node_modules dist coverage"
   },
   "author": "Formbricks <hola@formbricks.com>",
   "devDependencies": {
-    "@vercel/style-guide": "6.0.0",
+    "@eslint/js": "9.37.0",
     "@vitest/coverage-v8": "3.2.4",
+    "@vitest/eslint-plugin": "1.3.16",
+    "eslint": "9.37.0",
+    "eslint-config-prettier": "10.1.8",
+    "eslint-plugin-check-file": "3.3.0",
+    "eslint-plugin-import": "2.32.0",
+    "eslint-plugin-prettier": "5.5.4",
+    "happy-dom": "19.0.2",
     "terser": "5.44.0",
+    "typescript-eslint": "8.46.0",
     "vite": "7.1.9",
     "vite-plugin-dts": "4.5.4",
     "vitest": "3.2.4"

packages/js/src/index.test.ts

@@ -7,10 +7,11 @@ vi.mock("./lib/load-formbricks", () => ({
 
 import formbricks from "./index";
 import * as loadFormbricksModule from "./lib/load-formbricks";
+import { TFormbricks } from "./types/formbricks";
 
 // Get the mocked function
 const mockLoadFormbricksToProxy = vi.mocked(
-  loadFormbricksModule.loadFormbricksToProxy
+  loadFormbricksModule.loadFormbricksToProxy,
 );
 
 describe("formbricks proxy", () => {
@@ -60,7 +61,7 @@ describe("formbricks proxy", () => {
     expect(mockLoadFormbricksToProxy).toHaveBeenCalledWith(
       "setAttribute",
       key,
-      value
+      value,
     );
   });
 
@@ -74,7 +75,7 @@ describe("formbricks proxy", () => {
 
     expect(mockLoadFormbricksToProxy).toHaveBeenCalledWith(
       "setAttributes",
-      attributes
+      attributes,
     );
   });
 
@@ -85,7 +86,7 @@ describe("formbricks proxy", () => {
 
     expect(mockLoadFormbricksToProxy).toHaveBeenCalledWith(
       "setLanguage",
-      language
+      language,
     );
   });
 
@@ -107,7 +108,7 @@ describe("formbricks proxy", () => {
     await formbricks.registerRouteChange();
 
     expect(mockLoadFormbricksToProxy).toHaveBeenCalledWith(
-      "registerRouteChange"
+      "registerRouteChange",
     );
   });
 
@@ -121,7 +122,7 @@ describe("formbricks proxy", () => {
       },
     };
 
-    await (formbricks as any).init(initConfig);
+    await formbricks.init(initConfig);
 
     expect(mockLoadFormbricksToProxy).toHaveBeenCalledWith("init", initConfig);
   });
@@ -136,32 +137,30 @@ describe("formbricks proxy", () => {
       },
     };
 
-    // Cast to any to access the extended track method with properties
-    await (formbricks as any).track(trackCode, properties);
+    await formbricks.track(trackCode, properties);
 
     expect(mockLoadFormbricksToProxy).toHaveBeenCalledWith(
       "track",
       trackCode,
-      properties
+      properties,
     );
   });
 
   test("should handle any method call through the proxy", async () => {
-    const customMethod = "customMethod";
-    const args = ["arg1", "arg2", { key: "value" }];
+    const customMethod: keyof TFormbricks = "track";
+    const args = ["arg1"];
 
-    // Cast to any to call a method that doesn't exist in the type definition
-    await (formbricks as any)[customMethod](...args);
+    await formbricks[customMethod](args[0]);
 
     expect(mockLoadFormbricksToProxy).toHaveBeenCalledWith(
       customMethod,
-      ...args
+      args[0],
     );
   });
 
   test("should return the result of loadFormbricksToProxy calls", async () => {
     const mockResult = "test-result";
-    mockLoadFormbricksToProxy.mockResolvedValue(mockResult as any);
+    mockLoadFormbricksToProxy.mockResolvedValue(mockResult as unknown as void);
 
     const result = await formbricks.setEmail("test@example.com");
 
@@ -173,7 +172,7 @@ describe("formbricks proxy", () => {
     mockLoadFormbricksToProxy.mockRejectedValue(error);
 
     await expect(formbricks.setEmail("test@example.com")).rejects.toThrow(
-      "Test error"
+      "Test error",
     );
   });
 
@@ -190,12 +189,12 @@ describe("formbricks proxy", () => {
     expect(mockLoadFormbricksToProxy).toHaveBeenCalledTimes(4);
     expect(mockLoadFormbricksToProxy).toHaveBeenCalledWith(
       "setEmail",
-      "test@example.com"
+      "test@example.com",
     );
     expect(mockLoadFormbricksToProxy).toHaveBeenCalledWith(
       "setAttribute",
       "userId",
-      "user123"
+      "user123",
     );
     expect(mockLoadFormbricksToProxy).toHaveBeenCalledWith("track", "event1");
     expect(mockLoadFormbricksToProxy).toHaveBeenCalledWith("setLanguage", "en");
@@ -226,7 +225,7 @@ describe("proxy behavior", () => {
 
     expect(mockLoadFormbricksToProxy).toHaveBeenCalledWith(
       "setUserId",
-      "user123"
+      "user123",
     );
   });
 
@@ -236,7 +235,7 @@ describe("proxy behavior", () => {
     expect(mockLoadFormbricksToProxy).toHaveBeenCalledWith(
       "setAttribute",
       "key",
-      "value"
+      "value",
     );
   });
 
@@ -250,7 +249,7 @@ describe("proxy behavior", () => {
 
     expect(mockLoadFormbricksToProxy).toHaveBeenCalledWith(
       "setup",
-      setupConfig
+      setupConfig,
     );
   });
 });
@@ -264,15 +263,15 @@ describe("type safety", () => {
   test("should maintain type safety for known methods", () => {
     // These should compile without errors due to proper typing
     const testTypeSafety = () => {
-      formbricks.setup({ environmentId: "env", appUrl: "url" });
-      formbricks.track("event");
-      formbricks.setEmail("email");
-      formbricks.setAttribute("key", "value");
-      formbricks.setAttributes({ key: "value" });
-      formbricks.setLanguage("en");
-      formbricks.setUserId("user");
-      formbricks.logout();
-      formbricks.registerRouteChange();
+      void formbricks.setup({ environmentId: "env", appUrl: "url" });
+      void formbricks.track("event");
+      void formbricks.setEmail("email");
+      void formbricks.setAttribute("key", "value");
+      void formbricks.setAttributes({ key: "value" });
+      void formbricks.setLanguage("en");
+      void formbricks.setUserId("user");
+      void formbricks.logout();
+      void formbricks.registerRouteChange();
     };
 
     expect(testTypeSafety).not.toThrow();

packages/js/src/index.ts

@@ -14,14 +14,13 @@ declare global {
 const formbricksProxyHandler: ProxyHandler<TFormbricks> = {
   get(_target, prop, _receiver) {
     return (...args: unknown[]) =>
-      loadFormbricksToProxy(prop as string, ...args);
+      loadFormbricksToProxy(prop as keyof TFormbricks, ...args);
   },
 };
 
 const formbricks: TFormbricksCore = new Proxy(
   {} as TFormbricks,
-  formbricksProxyHandler
+  formbricksProxyHandler,
 );
 
-// eslint-disable-next-line import/no-default-export -- Required for UMD
 export default formbricks;