Server-Side Code Isolation in Start

[thefrana]

First,
I wanted to express my appreciation for these excellent packages.

I have a question regarding server-side code isolation: Is there a mechanism to ensure certain code runs exclusively on the server? For context:

• Remix uses a .server file naming convention to automatically exclude server code from the client bundle
• While createServerFn works well for simple functions, it's not ideal for more complex server modules (e.g., those requiring database connections)

Is there a recommended approach or best practice for handling this use case?

[ericwilhite]

I am experimenting with Start and had the same concerns about leaking sensitive things like db/api credentials and connections.

Couple of options I've found that are worth a test:

• import 'server-only': I don't particularly like this method because I don't want credentials leaking because of me forgetting to put the import in.

• vite-env-only: I've not tested this but by the looks of it I'm really hoping it works. I think this + an eslint rule to ensure createsServerFn calls only exist in a **/*.server.* pattern is going to be my preferred path forward.

[thefrana]

Thanks for the answer, we use vite-env-only extensively in other projects, but the TypeScript makes it return the actual value or undefined, which breaks normal flow. Also, the syntax is awful when you need to wrap everything in serverOnly$ macro.

We will try import 'server-only'. Thanks for that.

[ericwilhite]

It was my understanding with vite-env-only you could define everything within the vite plugin and not worry about using the server/client macros they expose?

I plan on testing it out next week using the *.server.ts pattern I mentioned.

[thefrana]

Yeah, you are absolutely right. I missed the option in the docs. Thanks for noticing!