Clear and concise description of the problem

I'm writing a plugin that collects a list of all the imported sass files and writes them to a single file instead. I can't write them one by one because sass throws "variable not defined", so the transform request for the combined file has to be stalled until no other modules are waiting to be resolved.

Suggested solution

Currently I'm using server._pendingRequests which is exactly what I was looking for, but it is a private property so really needs to be documented and exposed in a way that would be compatible with rollup. I proposed using this.pendingRequests in rollup/rollup#4294.

Alternative

No response

Additional context

https://github.com/vuetifyjs/vuetify-loader/blob/274ce9ced8da65107b7544f9cdb2d82d463be313/packages/vite-plugin/src/stylesPlugin.ts

vuetifyjs/vuetify-loader#225
rollup/rollup#4294

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