fix: enabling eslint ban-types rule and fixed string typing (#1313)

This PR reenables the ban-type eslint rule. This results in:
- a fix to a pre-existing typing bug where `String` type should be
`string`
- a more defined `Function` typing

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<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Low Risk**
> Mostly TypeScript typing/lint-only changes (replacing
`Function`/`String` with safer types) with minimal runtime impact; risk
is limited to potential downstream type incompatibilities in event
listener signatures.
> 
> **Overview**
> Re-enables stricter TypeScript linting around banned types by removing
the global `@typescript-eslint/ban-types` opt-out and adding targeted
suppressions where `Function` return types are required (e.g.
`listeners()`/`rawListeners()`).
> 
> Tightens public and test-facing callback typings across
clients/emitter APIs by replacing `Function` with `(...args: any[]) =>
void`, and fixes boxed `String` usages to primitive `string` in request
bodies and transactional store `selector` parameters (plus `deepCompact`
now constrains `T` to `object`).
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
09ceb8c. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: joker23

.eslintrc.js

@@ -37,7 +37,6 @@ module.exports = {
     ],
     '@typescript-eslint/no-explicit-any': 'off',
     '@typescript-eslint/ban-ts-comment': 'off',
-    '@typescript-eslint/ban-types': 'off',
     '@typescript-eslint/no-var-requires': 'off',
     '@typescript-eslint/no-unused-vars': [
       'error',

packages/sdk/browser/src/BrowserClient.ts

@@ -279,12 +279,12 @@ class BrowserClientImpl extends LDClientImpl {
     this.dataManager.setAutomaticStreamingState?.(hasListeners);
   }
 
-  override on(eventName: LDEmitterEventName, listener: Function): void {
+  override on(eventName: LDEmitterEventName, listener: (...args: any[]) => void): void {
     super.on(eventName, listener);
     this._updateAutomaticStreamingState();
   }
 
-  override off(eventName: LDEmitterEventName, listener: Function): void {
+  override off(eventName: LDEmitterEventName, listener: (...args: any[]) => void): void {
     super.off(eventName, listener);
     this._updateAutomaticStreamingState();
   }

packages/sdk/electron/__tests__/ElectronClient.ipcMain.test.ts

@@ -16,19 +16,21 @@ import ElectronInfo from '../src/platform/ElectronInfo';
 import { createMockLogger } from './testHelpers';
 
 type MockIpcMain = IpcMain & {
-  getHandler: (eventName: string) => Function | undefined;
+  getHandler: (eventName: string) => ((...args: any[]) => void) | undefined;
   removeAllListeners: (channel: string) => void;
   removeHandler: (channel: string) => void;
 };
-type MockPort = { postMessage: Function; close: Function };
+type MockPort = { postMessage: (...args: any[]) => void; close: (...args: any[]) => void };
 type MockIpcEvent = { returnValue?: any; ports?: MockPort[] };
 
 jest.mock('electron', () => {
-  const handlers = new Map<string, Function>();
+  const handlers = new Map<string, (...args: any[]) => void>();
   return {
     ipcMain: {
-      on: (eventName: string, handler: Function) => handlers.set(eventName, handler),
-      handle: (eventName: string, handler: Function) => handlers.set(eventName, handler),
+      on: (eventName: string, handler: (...args: any[]) => void) =>
+        handlers.set(eventName, handler),
+      handle: (eventName: string, handler: (...args: any[]) => void) =>
+        handlers.set(eventName, handler),
       getHandler: (eventName: string) => handlers.get(eventName),
       removeAllListeners: (channel: string) => handlers.delete(channel),
       removeHandler: (channel: string) => handlers.delete(channel),

packages/sdk/electron/__tests__/ElectronClient.mainProcess.test.ts

@@ -56,18 +56,19 @@ function createMockEventSourceThatDeliversPut(putData: object) {
   });
 }
 
-const handlers = new Map<string, Function>();
-const mockOn = jest.fn((eventName: string, handler: Function) => {
+const handlers = new Map<string, (...args: any[]) => void>();
+const mockOn = jest.fn((eventName: string, handler: (...args: any[]) => void) => {
   handlers.set(eventName, handler);
 });
-const mockHandle = jest.fn((eventName: string, handler: Function) => {
+const mockHandle = jest.fn((eventName: string, handler: (...args: any[]) => void) => {
   handlers.set(eventName, handler);
 });
 
 jest.mock('electron', () => ({
   ipcMain: {
-    on: (eventName: string, handler: Function) => mockOn(eventName, handler),
-    handle: (eventName: string, handler: Function) => mockHandle(eventName, handler),
+    on: (eventName: string, handler: (...args: any[]) => void) => mockOn(eventName, handler),
+    handle: (eventName: string, handler: (...args: any[]) => void) =>
+      mockHandle(eventName, handler),
     getHandler: (eventName: string) => handlers.get(eventName),
     removeAllListeners: (channel: string) => handlers.delete(channel),
     removeHandler: (channel: string) => handlers.delete(channel),

packages/sdk/electron/__tests__/renderer/ElectronRendererClient.test.ts

@@ -217,7 +217,7 @@ describe('given an instance of ElectronRendererClient', () => {
     const clientForSyncClose = new ElectronRendererClient(clientSideId);
     const syncCloseId = 'sync-close-id';
     (ldClientBridge.addEventHandler as jest.Mock).mockImplementation(
-      (_eventName: string, _cb: Function, onClose?: () => void) => {
+      (_eventName: string, _cb: (...args: any[]) => void, onClose?: () => void) => {
         onClose?.();
         return syncCloseId;
       },

packages/sdk/electron/src/platform/ElectronRequests.ts

@@ -122,7 +122,7 @@ export default class ElectronRequests implements platform.Requests {
     const impl = isSecure ? https : http;
 
     const headers = { ...options.headers };
-    let bodyData: String | Buffer | undefined = options.body;
+    let bodyData: string | Buffer | undefined = options.body;
 
     // For get requests we are going to automatically support compressed responses.
     // Note this does not affect SSE as the event source is not using this fetch implementation.

packages/sdk/server-node/src/Emits.ts

@@ -1,5 +1,6 @@
 import { EventEmitter } from 'events';
 
+// eslint-disable-next-line @typescript-eslint/ban-types
 export type EventableConstructor<T = {}> = new (...args: any[]) => T;
 export type Eventable = EventableConstructor<{ emitter: EventEmitter }>;
 
@@ -50,10 +51,12 @@ export function Emits<TBase extends Eventable>(Base: TBase) {
       return this.emitter.getMaxListeners();
     }
 
+    // eslint-disable-next-line @typescript-eslint/ban-types
     listeners(eventName: string | symbol): Function[] {
       return this.emitter.listeners(eventName);
     }
 
+    // eslint-disable-next-line @typescript-eslint/ban-types
     rawListeners(eventName: string | symbol): Function[] {
       return this.emitter.rawListeners(eventName);
     }

packages/sdk/server-node/src/LDClientNode.ts

@@ -133,10 +133,12 @@ class LDClientNode extends LDClientImpl implements LDClient {
     return this.emitter.getMaxListeners();
   }
 
+  // eslint-disable-next-line @typescript-eslint/ban-types
   listeners(eventName: string | symbol): Function[] {
     return this.emitter.listeners(eventName);
   }
 
+  // eslint-disable-next-line @typescript-eslint/ban-types
   rawListeners(eventName: string | symbol): Function[] {
     return this.emitter.rawListeners(eventName);
   }

packages/sdk/server-node/src/platform/NodeRequests.ts

@@ -126,7 +126,7 @@ export default class NodeRequests implements platform.Requests {
     const impl = isSecure ? https : http;
 
     const headers = { ...options.headers };
-    let bodyData: String | Buffer | undefined = options.body;
+    let bodyData: string | Buffer | undefined = options.body;
 
     // For get requests we are going to automatically support compressed responses.
     // Note this does not affect SSE as the event source is not using this fetch implementation.

packages/sdk/shopify-oxygen/contract-tests/src/index.ts

@@ -19,7 +19,7 @@ const port = 8000;
 const clientPool = new ClientPool();
 
 if (debugging) {
-  app.use((req: Request, res: Response, next: Function) => {
+  app.use((req: Request, res: Response, next: (...args: any[]) => void) => {
     console.debug('request', req.method, req.url);
     if (req.body) {
       console.debug('request', JSON.stringify(req.body, null, 2));