update ssr style injection strategy

Author: yyx990803

lib/component-normalizer.js

@@ -33,6 +33,9 @@ module.exports = function normalizeComponent (
     options.beforeCreate = existing
       ? [].concat(existing, injectStyles)
       : [injectStyles]
+    // used by ssr in case component is cached and beforeCreate
+    // never gets called
+    options._injectStyles = injectStyles
   }
 
   // scopedId

lib/loader.js

@@ -283,34 +283,43 @@ module.exports = function (content) {
 
   // add requires for styles
   if (parts.styles.length) {
-    var styleInjectionCode = 'function __injectVueStyle__ () {\n'
+    var styleInjectionCode =
+      'function __injectVueStyle__ () {\n'
     var cssModules = {}
     parts.styles.forEach(function (style, i) {
       // require style
       var requireString = style.src
         ? getRequireForImport('styles', style, style.scoped)
         : getRequire('styles', style, i, style.scoped)
 
+      var hasStyleLoader = requireString.indexOf('style-loader') > -1
+      var hasVueStyleLoader = requireString.indexOf('vue-style-loader') > -1
+      // vue-style-loader exposes inject functions during SSR so they are
+      // always called
+      var invokeStyle = isServer && hasVueStyleLoader
+        ? code => `;(${code}).__inject__()`
+        : code => code
+
       var moduleName = (style.module === true) ? '$style' : style.module
       // setCssModule
       if (moduleName) {
         if (moduleName in cssModules) {
           loaderContext.emitError('CSS module name "' + moduleName + '" is not unique!')
-          styleInjectionCode += requireString
+          styleInjectionCode += invokeStyle(requireString) + '\n'
         } else {
           cssModules[moduleName] = true
 
           // `(vue-)style-loader` exposes the name-to-hash map directly
           // `css-loader` exposes it in `.locals`
           // add `.locals` if the user configured to not use style-loader.
-          if (requireString.indexOf('style-loader') < 0) {
+          if (!hasStyleLoader) {
             requireString += '.locals'
           }
 
-          styleInjectionCode += 'this["' + moduleName + '"] = ' + requireString + '\n'
+          styleInjectionCode += invokeStyle('this["' + moduleName + '"] = ' + requireString) + '\n'
         }
       } else {
-        styleInjectionCode += requireString + '\n'
+        styleInjectionCode += invokeStyle(requireString) + '\n'
       }
     })
     styleInjectionCode += '}\n'

package.json

@@ -39,7 +39,7 @@
     "postcss-selector-parser": "^2.0.0",
     "source-map": "^0.5.6",
     "vue-hot-reload-api": "^2.0.11",
-    "vue-style-loader": "^2.0.0",
+    "vue-style-loader": "^3.0.0",
     "vue-template-es2015-compiler": "^1.2.2"
   },
   "peerDependencies": {