Support for vite ModuleRunner or other configLoader alternative

[Carnageous]

Clear and concise description of the problem

Vite introduced ModuleRunner recently, which is specifically useful for using vite with the option --configLoader runner so it can load .ts config files. I am, for example, using this approach to define a shared vite config from a package in a monorepo.

Now, with vitest's monorepo / project setup, it would be very helpful to load .ts config files from a sub-package using this approach, mainly because by default projects within a vitest workspace do not inherit all configurations but must be extended by a shared config (as per your documentation).

I like this design decision a lot, but having a shared config file in a monorepo is best done by defining it in a package that can be consumed by other packages.

Suggested solution

Allow vitest to load .ts files the same way vite can with the --configLoader runner flag. Or allow importing .ts files into vitest config files another way. An ideal config would look something like this:

import { defineProject, mergeConfig } from 'vitest/config';

import vitestConfigReact from '@my-monorepo/vitest-config/react-base';

// Note: This uses vitest's `defineProject`, not `defineConfig`, as workspace projects don't have all config options
export default mergeConfig(vitestConfigReact, defineProject({
  // ... my per-project-config
}));

Alternative

I am not at all fixed on supporting this ModuleRunner thing as I have no clue what the implications to Vitest would be. So any way to support .ts file imports would be great.

Additional context

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[Carnageous]

I figured you might want to know which errors one would currently get.

When running vitest with a vitest.config.ts file at the monorepo root and a sub-package for the vitest config, an error would look like this:

> vitest

failed to load config from /monorepo/packages/package-a/vitest.config.ts
failed to load config from /monorepo/packages/package-b/vite.config.ts

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ Startup Error ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯
AggregateError: Failed to initialize projects. There were errors during workspace setup. See below for more details.


errors]: [
    TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for /monorepo/packages/vite-config/react.ts

The folder structure looks like this:

repo/
├─ package-b/
│  ├─ vitest.config.ts // imports shared config
├─ package-a/
│  ├─ vitest.config.ts // imports shared config
├─ vitest-config/
│  ├─ react.ts // shared config
├─ vitest.config.ts // workspace

[hi-ogawa]

I think this is a matter of passing around configLoader flag to vite server config in two places, so probably we can allow this as Vitest cli flag

vitest/packages/vitest/src/node/create.ts

Lines 34 to 35 in 25e6fe8

	const config: ViteInlineConfig = {
	configFile: configPath,

vitest/packages/vitest/src/node/project.ts

Lines 731 to 733 in 25e6fe8

	const config: ViteInlineConfig = {
	...restOptions,
	configFile,

[MQYForverT]

I also want to talk about this issue and look forward to updates