process.env is not provided in worker in dev mode

[buffaybu]

Describe the bug

In dev mode, process.env is provided in main thread but not worker.

In production mode, process.env is replaced by define plugin.

Actually there is no description about process.env in the docs. Some libraries use process.env and the behavior mismatches with each case.

Reproduction

https://github.com/buffaybu/vite-env-example

During yarn dev, process in worker is undefined and accessing process.env will throw an error.

After yarn build, process.env is replaced with static value and no error will be thrown.

System Info

• vite version: 2.0.0-beta.50
• Operating System: macOS 11.1
• Node version: 14.15.0
• Package manager (npm/yarn/pnpm) and version: yarn