server function transformation plugin should exclude `node_modules`

[jasongitmail]

Which project does this relate to?

Start

Describe the bug

When using @cloudflare/vite-plugin instead of target: "cloudflare-module", the SSR build fails with:

[tanstack-start-core::server-fn:ssr] 'return' outside of function at position XXXXXX

The [tanstack-start-core::server-fn:ssr] transformation is parsing third-party library code in node_modules that it doesn't parse when using target: "cloudflare-module". The parser encounters JavaScript patterns it can't handle.

Suggested fix: The server function transformation plugin should exclude node_modules from processing, since server functions are defined in user code, not libraries. But to still allow any tanstack packages from node_modules to be transformed:

See PR #6285

Your Example Website or App

https://github.com/jasongitmail/tanstack-xlsx-repro

Steps to Reproduce the Bug or Issue

git clone https://github.com/jasongitmail/tanstack-xlsx-repro.git
cd tanstack-xlsx-repro
bun install

See steps in README.

Expected behavior

SSR build should succeed with @cloudflare/vite-plugin, matching the behavior of target: "cloudflare-module".

Screenshots or Videos

No response

Platform

    "@tanstack/react-query": "5.83.0",
    "@tanstack/react-router": "1.144.0",
    "@tanstack/react-router-devtools": "^1.144.0",
    "@tanstack/react-router-with-query": "1.130.17",
    "@tanstack/react-start": "1.145.3",
    "@tanstack/router-core": "1.144.0",
    "@tanstack/router-devtools-core": "^1.144.0",
    "@tanstack/router-generator": "1.145.2",
    "@tanstack/router-plugin": "1.145.2",

    "@vitejs/plugin-react": "^4.6.0",
    "@vitejs/plugin-react-oxc": "^0.2.3",
    "vite": "^7.0.4",
    "vite-env-only": "^3.0.3",
    "vite-tsconfig-paths": "^5.1.4",

Mac 26.1

Additional context

No response

[schiller-manuel]

what's the library code like that it can't handle?

[jasongitmail]

Generation of Excel files using xlsx-js-style. I'm not sure what characteristics of it are causing an issue, but that same dependency built fine in Tanstack Start when using target: "cloudflare-module".

[jasongitmail]

Closing. I'm not sure what coincidence of variables of dependency versions caused the earlier observed issue, but it's working today.