fix: only generate CSS source map when needed

close #1070

Author: yyx990803

lib/loader.js

@@ -85,7 +85,11 @@ module.exports = function (content) {
   const moduleId = 'data-v-' + hash(isProduction ? content : shortFilePath)
 
   let cssLoaderOptions = ''
-  if (!isProduction && this.sourceMap && options.cssSourceMap !== false) {
+  const cssSourceMap =
+    !isProduction &&
+    this.sourceMap &&
+    options.cssSourceMap !== false
+  if (cssSourceMap) {
     cssLoaderOptions += '?sourceMap'
   }
   if (isProduction) {
@@ -97,7 +101,16 @@ module.exports = function (content) {
 
   let output = ''
   const bustCache = !isProduction && options.cacheBusting !== false
-  const parts = parse(content, fileName, this.sourceMap, sourceRoot, bustCache)
+
+  const parts = parse(
+    content,
+    fileName,
+    this.sourceMap,
+    sourceRoot,
+    bustCache,
+    cssSourceMap
+  )
+
   const hasScoped = parts.styles.some(({ scoped }) => scoped)
   const templateAttrs =
     parts.template && parts.template.attrs && parts.template.attrs

lib/parser.js

@@ -6,7 +6,7 @@ const SourceMapGenerator = require('source-map').SourceMapGenerator
 const splitRE = /\r?\n/g
 const emptyRE = /^(?:\/\/)?\s*$/
 
-module.exports = (content, filename, needMap, sourceRoot, bustCache) => {
+module.exports = (content, filename, needMap, sourceRoot, bustCache, needCSSMap) => {
   const cacheKey = hash(filename + content)
   // source-map cache busting for hot-reloadded modules
   const filenameWithHash = bustCache
@@ -24,7 +24,7 @@ module.exports = (content, filename, needMap, sourceRoot, bustCache) => {
         sourceRoot
       )
     }
-    if (output.styles) {
+    if (needCSSMap && output.styles) {
       output.styles.forEach(style => {
         if (!style.src) {
           style.map = generateSourceMap(