refactor(server): clean up code review issues in plugin child TS conversion

- Remove `return false` from uncaughtException/unhandledRejection handlers (Node.js ignores it)
- Remove dead `RunPlugins.wrapChildPromise` method and its `UNDEFINED_SERIALIZED` constant (all call sites use the imported util function)
- Make `validateEvent` params `event` and `handler` required; remove unnecessary `!` assertion
- Fix `(val as Function).name` to use a typed object cast
- Collapse verbose 3-line comment in ProjectConfigIpc.ts to one line
- Remove trailing whitespace from tsconfig.json

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/data-context/src/data/ProjectConfigIpc.ts

@@ -20,10 +20,7 @@ const pkg = require('@packages/root')
 const debug = debugLib(`cypress:lifecycle:ProjectConfigIpc`)
 const debugVerbose = debugLib(`cypress-verbose:lifecycle:ProjectConfigIpc`)
 
-// If in development, use the TypeScript require_async_child file
-// Otherwise, the binary will be using the transpiled version of the Typescript file
-// into whatever @packages/server JavaScript target is defined in the tsconfig.json
-
+// In dev the .ts source exists; in production only the compiled .js is present.
 const resolveRequireAsyncChildPath = (): string => {
   const serverRoot = path.dirname(require.resolve('@packages/server/package.json'))
   const tsPath = path.join(serverRoot, 'lib/plugins/child/require_async_child.ts')

packages/server/lib/plugins/child/require_async_child.ts

@@ -33,7 +33,6 @@ const span = telemetry.startSpan({ name: 'child:process', active: true })
 debug('child:process span initialized')
 suppressWarnings()
 
-// note: what is this doing?
 gracefulify(fs)
 const ipc = util.wrapIpc(process as unknown as util.WrappedIpcProcess)
 

packages/server/lib/plugins/child/run_plugins.ts

@@ -24,8 +24,6 @@ import type {
 
 const debug = debugLib(`cypress:lifecycle:child:RunPlugins:${process.pid}`)
 
-const UNDEFINED_SERIALIZED = '__cypress_undefined__'
-
 export class RunPlugins {
   private ipc: PluginChildIpc
   private projectRoot: string
@@ -186,27 +184,6 @@ export class RunPlugins {
     return (event.handler as (...handlerArgs: any[]) => any)(...args)
   }
 
-  wrapChildPromise (
-    invoke: (eventId: number, args?: any[]) => any,
-    ids: PluginInvokeIds,
-    args: any[] = [],
-  ) {
-    return Promise.try(() => {
-      return invoke(ids.eventId, args)
-    })
-    .then((value) => {
-      // undefined is coerced into null when sent over ipc, but we need
-      // to differentiate between them for 'task' event
-      if (value === undefined) {
-        value = UNDEFINED_SERIALIZED
-      }
-
-      return this.ipc.send(`promise:fulfilled:${ids.invocationId}`, null, value)
-    }).catch((err) => {
-      return this.ipc.send(`promise:fulfilled:${ids.invocationId}`, serializeError(err))
-    })
-  }
-
   taskGetBody (ids: PluginInvokeIds, args: any[]) {
     const [event] = args
     const taskEvent = _.find(this.registeredEventsById, { event: 'task' })

packages/server/lib/plugins/child/run_require_async_child.ts

@@ -29,8 +29,6 @@ export function run (ipc: PluginChildIpc, file: string, projectRoot: string): vo
   process.on('uncaughtException', (err) => {
     debug('uncaught exception:', util.serializeError(err))
     ipc.send('childProcess:unhandledError', util.serializeError(err))
-
-    return false
   })
 
   process.on('unhandledRejection', (event: BluebirdRejectionEvent | unknown) => {
@@ -45,8 +43,6 @@ export function run (ipc: PluginChildIpc, file: string, projectRoot: string): vo
     }
 
     ipc.send('childProcess:unhandledError', util.serializeError(err as Error))
-
-    return false
   })
 
   const isValidSetupNodeEvents = (config: ConfigFileExport, testingType: TestingType): boolean => {
@@ -142,7 +138,7 @@ export function run (ipc: PluginChildIpc, file: string, projectRoot: string): vo
       const result = (configFileExport.default || configFileExport) as ConfigFileExport
 
       const replacer = (_key: string, val: unknown) => {
-        return typeof val === 'function' ? `[Function ${(val as Function).name}]` : val
+        return typeof val === 'function' ? `[Function ${(val as { name: string }).name}]` : val
       }
 
       ipc.send('loadConfig:reply', { initialConfig: JSON.stringify(result, replacer), requires: util.nonNodeRequires() })

packages/server/lib/plugins/child/validate_event.ts

@@ -47,12 +47,12 @@ const eventValidators: Record<string, EventValidator> = {
 }
 
 export const validateEvent = (
-  event?: string,
-  handler?: unknown,
+  event: string,
+  handler: unknown,
   config?: Cypress.PluginConfigOptions,
   errConstructorFn?: () => void,
 ): ValidateEventResult => {
-  const validator = event ? eventValidators[event] : undefined
+  const validator = eventValidators[event]
 
   if (!validator) {
     const userEvents = _.reject(_.keys(eventValidators), (registeredEvent) => {
@@ -74,7 +74,7 @@ export const validateEvent = (
     }
   }
 
-  const result = validator(event!, handler, config)
+  const result = validator(event, handler, config)
 
   if (!result.isValid) {
     result.error.name = 'InvalidEventHandlerError'

packages/server/tsconfig.json

@@ -9,6 +9,6 @@
   ],
   "compilerOptions": {
     "lib": ["esnext"],
-    "target": "ES2022",    
+    "target": "ES2022",
   }
 }