# HowTo: Patch Vite to expose Rollup cache

Goal is to access and use the Rollup cache between builds using Vite `builder.build()`.

## 1. Find and patch the `buildEnvironment` function
(May be in `node_modules/vite/dist/node/chunks/dep-M1IYMR16.js`, or do a search in `node_modules/vite/dist` for `async function buildEnvironment`)

Make the following changes:

async function buildEnvironment(environment, rollupCache /* add this */) {

    if (rollupCache) { rollupOptions.cache = rollupCache; } // add this
    bundle = await rollup(rollupOptions);

And replace

    return Array.isArray(outputs) ? res : res[0];

with

    const returnValue = Array.isArray(outputs) ? res : res[0]
    returnValue.cache = bundle.cache
    return returnValue

## 2. Find and patch `ViteBuilder.build`
(May be in `node_modules/vite/dist/node/chunks/dep-M1IYMR16.js`, or do a search in `node_modules/vite/dist` for `return buildEnvironment(environment)`)

Change it to:

    async build(environment, rollupCache) {
      return buildEnvironment(environment, rollupCache);
    }

## References
* https://github.com/onejs/one/blob/8b86518b5009d821b95a90276de67f963735b88d/packages/vxrn/src/utils/fork/vite/build.ts

## Notes

  const rollupOptions = {
    preserveEntrySignatures: ssr ? "allow-extension" : libOptions ? "strict" : false,
    cache: rollupCache /* add this */ || options.watch ? undefined : false,
    ...options.rollupOptions,

The above isn’t working, `rollupOptions.cache` still seems to be false at the end. Probably `options.rollupOptions` is overriding it.