feat(compiler-sfc): additionalData support for css preprocessors (#2126)

close https://github.com/vitejs/vite/issues/520

packages/compiler-sfc/src/stylePreprocessors.ts

@@ -1,12 +1,14 @@
 import merge from 'merge-source-map'
 import { RawSourceMap } from 'source-map'
 import { SFCStyleCompileOptions } from './compileStyle'
+import { isFunction } from '@vue/shared'
 
 export type StylePreprocessor = (
   source: string,
   map: RawSourceMap | undefined,
   options: {
     [key: string]: any
+    additionalData?: string | ((source: string, filename: string) => string)
     filename: string
   },
   customRequire: SFCStyleCompileOptions['preprocessCustomRequire']
@@ -24,7 +26,7 @@ const scss: StylePreprocessor = (source, map, options, load = require) => {
   const nodeSass = load('sass')
   const finalOptions = {
     ...options,
-    data: (options.additionalData || '') + source,
+    data: getSource(source, options.filename, options.additionalData),
     file: options.filename,
     outFile: options.filename,
     sourceMap: !!map
@@ -66,7 +68,7 @@ const less: StylePreprocessor = (source, map, options, load = require) => {
   let result: any
   let error: Error | null = null
   nodeLess.render(
-    source,
+    getSource(source, options.filename, options.additionalData),
     { ...options, syncImport: true },
     (err: Error | null, output: any) => {
       error = err
@@ -117,6 +119,18 @@ const styl: StylePreprocessor = (source, map, options, load = require) => {
   }
 }
 
+function getSource(
+  source: string,
+  filename: string,
+  additionalData?: string | ((source: string, filename: string) => string)
+) {
+  if (!additionalData) return source
+  if (isFunction(additionalData)) {
+    return additionalData(source, filename)
+  }
+  return additionalData + source
+}
+
 export type PreprocessLang = 'less' | 'sass' | 'scss' | 'styl' | 'stylus'
 
 export const processors: Record<PreprocessLang, StylePreprocessor> = {