feat(css): support resolving stylesheets from exports map

packages/vite/src/node/plugins/css.ts

@@ -731,6 +731,7 @@ function createCSSResolvers(config: ResolvedConfig): CSSAtImportResolvers {
         (cssResolve = config.createResolver({
           extensions: ['.css'],
           mainFields: ['style'],
+          conditions: ['style'],
           tryIndex: false,
           preferRelative: true,
         }))
@@ -743,6 +744,7 @@ function createCSSResolvers(config: ResolvedConfig): CSSAtImportResolvers {
         (sassResolve = config.createResolver({
           extensions: ['.scss', '.sass', '.css'],
           mainFields: ['sass', 'style'],
+          conditions: ['sass', 'style'],
           tryIndex: true,
           tryPrefix: '_',
           preferRelative: true,
@@ -756,6 +758,7 @@ function createCSSResolvers(config: ResolvedConfig): CSSAtImportResolvers {
         (lessResolve = config.createResolver({
           extensions: ['.less', '.css'],
           mainFields: ['less', 'style'],
+          conditions: ['less', 'style'],
           tryIndex: false,
           preferRelative: true,
         }))

playground/css/__tests__/css.spec.ts

@@ -285,6 +285,14 @@ test('@import dependency w/ sass entry', async () => {
   expect(await getColor('.css-dep-sass')).toBe('orange')
 })
 
+test('@import dependency w/ style export mapping', async () => {
+  expect(await getColor('.css-dep-exports')).toBe('purple')
+})
+
+test('@import dependency w/ sass export mapping', async () => {
+  expect(await getColor('.css-dep-exports-sass')).toBe('orange')
+})
+
 test('@import dependency w/out package scss', async () => {
   expect(await getColor('.sass-dep')).toBe('lavender')
 })

playground/css/css-dep-exports/index.js

@@ -0,0 +1 @@
+throw new Error('should not be imported')

playground/css/css-dep-exports/package.json

@@ -0,0 +1,12 @@
+{
+  "name": "@vitejs/test-css-dep-exports",
+  "private": true,
+  "version": "1.0.0",
+  "exports": {
+    ".": {
+      "sass": "./style.scss",
+      "style": "./style.css",
+      "import": "./index.js"
+    }
+  }
+}

playground/css/css-dep-exports/style.css

@@ -0,0 +1,3 @@
+.css-dep-exports {
+  color: purple;
+}

playground/css/css-dep-exports/style.scss

@@ -0,0 +1,3 @@
+.css-dep-exports-sass {
+  color: orange;
+}

playground/css/dep.css

@@ -1 +1,2 @@
 @import '@vitejs/test-css-dep';
+@import '@vitejs/test-css-dep-exports';

playground/css/index.html

@@ -125,6 +125,13 @@ <h1>CSS</h1>
     @import dependency w/ sass entrypoints: this should be orange
   </p>
 
+  <p class="css-dep-exports">
+    @import dependency w/ style export mapping: this should be purple
+  </p>
+  <p class="css-dep-exports-sass">
+    @import dependency w/ sass export mapping: this should be orange
+  </p>
+
   <p class="dir-dep">PostCSS dir-dependency: this should be grey</p>
   <p class="dir-dep-2">
     PostCSS dir-dependency (file 2): this should be grey too

playground/css/package.json

@@ -13,6 +13,7 @@
   },
   "devDependencies": {
     "@vitejs/test-css-dep": "link:./css-dep",
+    "@vitejs/test-css-dep-exports": "link:./css-dep-exports",
     "@vitejs/test-css-js-dep": "file:./css-js-dep",
     "fast-glob": "^3.2.12",
     "less": "^4.1.3",

playground/css/sass.scss

@@ -1,6 +1,7 @@
 @import '=/nested'; // alias + custom index resolving -> /nested/_index.scss
 @import '=/nested/partial'; // sass convention: omitting leading _ for partials
 @import '@vitejs/test-css-dep'; // package w/ sass entry points
+@import '@vitejs/test-css-dep-exports'; // package with a sass export mapping
 @import 'virtual-dep'; // virtual file added through importer
 @import '=/pkg-dep'; // package w/out sass field
 @import '=/weapp.wxss'; // wxss file