[Bug?]: `set-cookie`s from server action's response `return` being overwritten with `flash` cookie

[samualtnorman]

Duplicates

• [X] I have searched the existing issues

Latest version

• [X] I have tested the latest version

Current behavior 😯

Solid Start overwrites set-cookie's from my server action's returned response with flash cookie in no JS mode.

Expected behavior 🤔

For the client to receive my set-cookie headers.

Steps to reproduce 🕹

return redirect("/foo", { headers: { "set-cookie": "foo=bar" } })

in server action

Context 🔦

I'm trying to set a cookie from a server action.

Your environment 🌎

System:
    OS: NixOS 24.05.5518.ecbc1ca8ffd6 (Uakari) x86_64
    CPU: 12th Gen Intel(R) Core(TM) i5-12500 (12) @ 4.60 GHz
Binaries:
    Node: 22.6.0
    PNPM: 9.12.0
npmPackages:
    @solidjs/meta 0.29.4
    @solidjs/router 0.14.7
    @solidjs/start 1.0.8
    solid-js 1.9.1

[samualtnorman]

For other people running into this issue, I am currently using this patch as a workaround:

diff --git a/dist/runtime/server-handler.js b/dist/runtime/server-handler.js
index 9f86080139b32ce71dcc27103ecd26549191cdbc..9aab397f46d729b2a6bc236c6b542018b407e364 100644
--- a/dist/runtime/server-handler.js
+++ b/dist/runtime/server-handler.js
@@ -207,28 +207,28 @@ async function handleServerFunction(h3Event) {
 function handleNoJS(result, request, parsed, thrown) {
     const url = new URL(request.url);
     const isError = result instanceof Error;
-    let redirectUrl = new URL(request.headers.get("referer")).toString();
     let statusCode = 302;
-    if (result instanceof Response && result.headers.has("Location")) {
-        redirectUrl = new URL(result.headers.get("Location"), url.origin + import.meta.env.SERVER_BASE_URL).toString();
-        statusCode = getExpectedRedirectStatus(result);
+    let headers;
+    if (result instanceof Response) {
+        headers = new Headers(result.headers)
+        if (result.headers.has("Location")) {
+            headers.set(`Location`, new URL(result.headers.get("Location"), url.origin + import.meta.env.SERVER_BASE_URL).toString())
+            statusCode = getExpectedRedirectStatus(result);
+        }
+    } else
+        headers = new Headers({ Location: new URL(request.headers.get("referer")).toString() })
+    if (result) {
+        headers.append("Set-Cookie", `flash=${JSON.stringify({
+            url: url.pathname + encodeURIComponent(url.search),
+            result: isError ? result.message : result,
+            thrown: thrown,
+            error: isError,
+            input: [...parsed.slice(0, -1), [...parsed[parsed.length - 1].entries()]]
+        })}; Secure; HttpOnly;`)
     }
     return new Response(null, {
         status: statusCode,
-        headers: {
-            Location: redirectUrl,
-            ...(result
-                ? {
-                    "Set-Cookie": `flash=${JSON.stringify({
-                        url: url.pathname + encodeURIComponent(url.search),
-                        result: isError ? result.message : result,
-                        thrown: thrown,
-                        error: isError,
-                        input: [...parsed.slice(0, -1), [...parsed[parsed.length - 1].entries()]]
-                    })}; Secure; HttpOnly;`
-                }
-                : {})
-        }
+        headers
     });
 }
 let App;

[ryansolid]

This looks pretty good. I will add it in, but PR is more than welcome next time.