feat(dev): expose setReactRouterDevLoadContext

[albertusdev]

Purpose

This PR exposes the setReactRouterDevLoadContext function from the vite plugin, allowing developers to easily set a custom load context for the dev server without requiring a custom server entrypoint.

Problem

Currently, to provide a custom "load context" for server-side loaders and actions during development, developers must either:

1. Set up a custom server entrypoint with more complex configuration, as shown in Vercel's documentation:

// vite.config.ts
export default defineConfig(({ isSsrBuild }) => ({
  build: {
    rollupOptions: isSsrBuild
      ? {
          input: './server/app.ts',
        }
      : undefined,
  },
  plugins: [reactRouter(), /* other plugins */],
}));

// server/app.ts
export default app.fetch;

2. Or even goes to the length of implementing a custom server & dev server as seen in https://github.com/remix-run/react-router-templates/tree/main/node-custom-server

Both approaches require additional configuration and setup just to supply environment variables or other data to loaders and actions during development.

Solution

By exposing the existing setReactRouterDevLoadContext function, developers can achieve the same result with a much simpler approach:

// vite.config.ts
import { reactRouter, setReactRouterDevLoadContext } from '@react-router/dev/vite';

// Set a custom load context for the dev server
setReactRouterDevLoadContext((request) => {
  return {
    env: {
      API_KEY: process.env.API_KEY,
      // Other environment variables
    },
    // Other context data
  };
});

export default {
  plugins: [
    reactRouter(),
    // Other plugins
  ],
};

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[remix-cla-bot]

Hi @albertusdev,

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[remix-cla-bot]

Thank you for signing the Contributor License Agreement. Let's get this merged! 🥳

[albertusdev]

hi @brophdawg11! sorry for the tag here, not sure which contributors should I ping to get this small PR reviewed. appreciate your help here!

[Copilot]

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

[markdalgleish]

Thanks for the PR!

One concern I have with the approach in this PR is it assumes the server is running in the same environment as Vite, but with our newly added support for the Vite Environment API, this is no longer guaranteed. For example, when using vite-plugin-cloudflare, your app code is running in workerd and doesn't use the context passed to setReactRouterDevLoadContext. For these consumers, this feature would appear to be broken.

Any API for make setting a load context easier would probably work better a file to be configured in your React Router config, e.g. export default { loadContextFile: "load-context.ts" }, and maybe even provide a default value for this if a new future flag is enabled, this way we can ensure it's executed within the same environment as your app code.

We'd still need to discuss whether this is something we want to support, so could you help us by providing a bit more detail about your use case?