feat: introduce RunnableDevEnvironment

[sheremet-va]

Description

This PR introduces a new concept to the Environment API - the RunnableDevEnvironment. This is the environment that has a module runner in the same process. You can access it directly as environment.runner. The runner itself is evaluated eagerly when it's accessed for the first time.

By default, Vite SSR dev environment is a runnable environment. Due to environments being available during the build, there are some constraints in typing. You can either cast it to RunnableDevEnvironment or type guard it with isRunnableDevEnvironment.

import { createServer, isRunnableDevEnvironment } from 'vite'
import type { RunnableDevEnvironment } from 'vite'

const server = createServer()
const ssrEnvironment = server.environments.ssr as RunnableDevEnvironment

if (isRunnableDevEnvironment(ssrEnvironment)) {
  await ssrEnvironment.runner.import('/entry-point.js')
}

You can create your own runnable environments using the createRunnableDevEnvironment function:

import { createRunnableDevEnvironment } from 'vite'

const environment = createRunnableDevEnvironment(name, config)
await environment.runner.import('/entry-point.js')

You can configure the runner with the runner option (the previous runner option was renamed to remoteRunner):

import { createRunnableDevEnvironment, createServerModuleRunner } from 'vite'

const environment = createRunnableDevEnvironment(name, config, {
  runner: (env) => createServerModuleRunner(env, { hmr: false })
})
await environment.runner.import('/entry-point.js')

[stackblitz]

Run & review this pull request in StackBlitz Codeflow.