feat(config): add envDir option (#3407)

Co-authored-by: Alec Larson <1925840+aleclarson@users.noreply.github.com>

docs/config/index.md

@@ -322,6 +322,15 @@ export default async ({ command, mode }) => {
 
   Set to `false` to prevent Vite from clearing the terminal screen when logging certain messages. Via command line, use `--clearScreen false`.
 
+### envDir
+
+- **Type:** `string`
+- **Default:** `root`
+
+  The directory from which `.env` files are loaded. Can be an absolute path, or a path relative to the project root.
+
+  See [here](/guide/env-and-mode#env-files) for more about environment files.
+
 ## Server Options
 
 ### server.host

docs/guide/env-and-mode.md

@@ -24,7 +24,7 @@ It will also replace these strings appearing in JavaScript strings and Vue templ
 
 ## `.env` Files
 
-Vite uses [dotenv](https://github.com/motdotla/dotenv) to load additional environment variables from the following files in your project root:
+Vite uses [dotenv](https://github.com/motdotla/dotenv) to load additional environment variables from the following files in your [environment directory](/config/#envDir):
 
 ```
 .env                # loaded in all cases

packages/vite/src/node/config.ts

@@ -155,6 +155,12 @@ export interface UserConfig {
    * Default: true
    */
   clearScreen?: boolean
+  /**
+   * Environment files directory. Can be an absolute path, or a path relative from
+   * the location of the config file itself.
+   * @default root
+   */
+  envDir?: string
   /**
    * Import aliases
    * @deprecated use `resolve.alias` instead
@@ -304,7 +310,10 @@ export async function resolveConfig(
   }
 
   // load .env files
-  const userEnv = inlineConfig.envFile !== false && loadEnv(mode, resolvedRoot)
+  const envDir = config.envDir
+    ? normalizePath(path.resolve(resolvedRoot, config.envDir))
+    : resolvedRoot
+  const userEnv = inlineConfig.envFile !== false && loadEnv(mode, envDir)
 
   // Note it is possible for user to have a custom mode, e.g. `staging` where
   // production-like behavior is expected. This is indicated by NODE_ENV=production
@@ -893,7 +902,7 @@ async function loadConfigFromBundledFile(
 
 export function loadEnv(
   mode: string,
-  root: string,
+  envDir: string,
   prefix = 'VITE_'
 ): Record<string, string> {
   if (mode === 'local') {
@@ -920,7 +929,7 @@ export function loadEnv(
   }
 
   for (const file of envFiles) {
-    const path = lookupFile(root, [file], true)
+    const path = lookupFile(envDir, [file], true)
     if (path) {
       const parsed = dotenv.parse(fs.readFileSync(path), {
         debug: !!process.env.DEBUG || undefined