fix(response): correctly deep-merge options

 don't allow `undefined` to overwrite a non-nullish value

Author: Lordfirespeed

packages/cookie/src/index.ts

@@ -55,16 +55,16 @@ export function parse(
   return obj
 }
 
-export type SerializeOptions = Partial<{
-  encode: (str: string) => string
-  maxAge: number
-  domain: string
-  path: string
-  httpOnly: boolean
-  secure: boolean
-  sameSite: boolean | "Strict" | "strict" | "Lax" | "lax" | "None" | "none" | string
-  expires: Date
-}>
+export type SerializeOptions = {
+  encode?: ((str: string) => string) | null | undefined
+  maxAge?: number | null | undefined
+  domain?: string | null | undefined
+  path?: string | null | undefined
+  httpOnly?: boolean | null | undefined
+  secure?: boolean | null | undefined
+  sameSite?: boolean | "Strict" | "strict" | "Lax" | "lax" | "None" | "none" | string | null | undefined
+  expires?: Date | null | undefined
+}
 
 export function serialize(name: string, val: string, options: SerializeOptions = {}): string {
   options.encode ??= encodeURIComponent

packages/response/src/cookie.ts

@@ -4,8 +4,9 @@ import type { HasIncomingHeaders, HasOutgoingHeaders, HasReq } from "./types"
 
 type SetCookieResponse = HasOutgoingHeaders & HasReq<HasIncomingHeaders>
 export type SetCookieOptions = cookie.SerializeOptions & {
-  sign?: ((cookieValue: string) => string) | undefined
+  sign?: ((cookieValue: string) => string) | undefined | null
 }
+
 export function setCookie(res: SetCookieResponse, name, value: string, options: SetCookieOptions = {}): void {
   if (options.maxAge != null) {
     options.expires = new Date(Date.now() + options.maxAge)

packages/response/src/prototype.ts

@@ -119,7 +119,19 @@ export class Response<Req extends Request<unknown> = Request<unknown>> extends S
 
   cookie(name: string, value: string, options?: SetCookieOptions): this {
     if (options == null) options = this.appSettings?.setCookieOptions
-    else options = Object.assign({}, this.appSettings?.setCookieOptions, options)
+    else {
+      options = [this.appSettings?.setCookieOptions, options].reduce<SetCookieOptions>(
+        (optionsAccumulator, optionsSource) => {
+          if (optionsSource == null) return optionsAccumulator
+          for (const [key, value] of Object.entries(optionsSource)) {
+            if (value === undefined) continue
+            optionsAccumulator[key] = value
+          }
+          return optionsAccumulator
+        },
+        {},
+      )
+    }
     setCookie(this, name, value, options)
     return this
   }