fix(#518): guard cookie writes when response headers already sent

src/runtime/plugins/supabase.server.ts

@@ -1,7 +1,8 @@
 import { createServerClient, parseCookieHeader } from '@supabase/ssr'
-import { getHeader, setCookie } from 'h3'
+import { getHeader } from 'h3'
 import type { SupabaseClient } from '@supabase/supabase-js'
 import { fetchWithRetry } from '../utils/fetch-retry'
+import { setCookies } from '../utils/cookies'
 import { serverSupabaseUser, serverSupabaseSession } from '../server/services'
 import { useSupabaseSession } from '../composables/useSupabaseSession'
 import { useSupabaseUser } from '../composables/useSupabaseUser'
@@ -21,13 +22,7 @@ export default defineNuxtPlugin({
       ...clientOptions,
       cookies: {
         getAll: () => parseCookieHeader(getHeader(event, 'Cookie') ?? ''),
-        setAll: (
-          cookies: {
-            name: string
-            value: string
-            options: CookieOptions
-          }[],
-        ) => cookies.forEach(({ name, value, options }) => setCookie(event, name, value, options)),
+        setAll: (cookies: { name: string, value: string, options: CookieOptions }[]) => setCookies(event, cookies),
       },
       cookieOptions: {
         ...cookieOptions,

src/runtime/server/services/serverSupabaseClient.ts

@@ -1,7 +1,9 @@
 import type { SupabaseClient } from '@supabase/supabase-js'
-import { createServerClient, parseCookieHeader, type CookieOptions } from '@supabase/ssr'
-import { getHeader, setCookie, type H3Event } from 'h3'
+import { createServerClient, parseCookieHeader } from '@supabase/ssr'
+import { getHeader, type H3Event } from 'h3'
 import { fetchWithRetry } from '../../utils/fetch-retry'
+import { setCookies } from '../../utils/cookies'
+import type { CookieOptions } from '#app'
 import { useRuntimeConfig } from '#imports'
 // @ts-expect-error - `#supabase/database` is a runtime alias
 import type { Database } from '#supabase/database'
@@ -17,13 +19,7 @@ export const serverSupabaseClient: <T = Database>(event: H3Event) => Promise<Sup
       auth,
       cookies: {
         getAll: () => parseCookieHeader(getHeader(event, 'Cookie') ?? ''),
-        setAll: (
-          cookies: {
-            name: string
-            value: string
-            options: CookieOptions
-          }[],
-        ) => cookies.forEach(({ name, value, options }) => setCookie(event, name, value, options)),
+        setAll: (cookies: { name: string, value: string, options: CookieOptions }[]) => setCookies(event, cookies),
       },
       cookieOptions: {
         ...cookieOptions,

src/runtime/utils/cookies.ts

@@ -0,0 +1,25 @@
+import { setCookie, type H3Event } from 'h3'
+import type { CookieOptions } from '#app'
+
+export function setCookies(
+  event: H3Event,
+  cookies: {
+    name: string
+    value: string
+    options: CookieOptions
+  }[],
+) {
+  const response = event.node.res
+  const headersWritable = () => !response.headersSent && !response.writableEnded
+
+  if (!headersWritable()) {
+    return
+  }
+
+  for (const { name, value, options } of cookies) {
+    if (!headersWritable()) {
+      break
+    }
+    setCookie(event, name, value, options)
+  }
+}