Tim Neutkens bf6784f78b Turbopack: Add postcss.config.ts support (#89049) ...

### What?

Adds support for TypeScript PostCSS configuration files in Turbopack.

### Why?

Users can write their PostCSS configuration in TypeScript for better
type safety and IDE support. This was already supported in webpack but
was missing in Turbopack.

### How?

Added the following TypeScript config file names to Turbopack's PostCSS
config detection:
- `postcss.config.ts`, `postcss.config.mts`, `postcss.config.cts`
- `.postcssrc.ts`, `.postcssrc.mts`, `.postcssrc.cts`
- `.config/postcssrc.ts`, `.config/postcssrc.mts`,
`.config/postcssrc.cts`

Also updated the Turbopack documentation to reflect the supported config
file extensions (`.js`, `.mjs`, `.cjs`, `.ts`, `.mts`, `.cts`).

### Testing

Added e2e tests that verify the TypeScript PostCSS config is actually
loaded and applied by using a custom plugin that transforms colors.
Tests cover:
- `postcss.config.ts`
- `postcss.config.mts`
- `postcss.config.cts`
- `.postcssrc.ts`

2026-01-27 11:59:35 +01:00

..

postcss-config

…

postcss-config-cts

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postcss-config-mts

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postcssrc

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index.test.ts

…