How to properly use extendZodWithOpenApi(z)

[ajiohjesse]

I'm trying to build an express starter template with this library but I have a few issues.

The docs say to call the extendZodWithOpenApi(z) function in a common entry point which I did, inside my server.ts file but it doesn't work. I ended up having to call the function in two more random files (i.e docs.ts and another post.schema.ts file) to get it to work but I'm sure this is not a recommended pattern as stated in the docs to only call the function once.

My setup is this: my docs.ts file does the actual generation of the openapi document while I have several *.registry.ts files that register the components and component paths, and also *.schema.ts files where I define reusable zod schemas for both for validation and for usage with the openapi registries.

I tried creating a zod-extend.ts file and using this solution:

//zod-extend.ts

import { extendZodWithOpenApi } from '@asteasolutions/zod-to-openapi';
import { z } from 'zod';

extendZodWithOpenApi(z);

// package.json

  "scripts": {
    "start": "tsx --import ./zod-extend.ts ./index.ts",

It works in dev because I'm using tsx but the production build still throws the error .openApi is not a function.

I just want to understand how to set this up properly.