Merge branch 'dev' of https://github.com/dcloudio/uni-app into alpha

packages/vue-cli-plugin-uni/packages/@vue/component-compiler-utils/dist/stylePlugins/scoped.js

@@ -58,8 +58,14 @@ exports.default = postcss.plugin('add-id', (options) => (root) => {
                     // So all leading spaces must be eliminated to avoid problems.
                     selector.first.spaces.before = '';
                 }
-                // fixed by xxxxxx (h5 平台继续使用 attribute,其他平台使用 className)
-                if(process.env.UNI_PLATFORM === 'h5'){
+                // fixed by xxxxxx (h5,app-plus v3 平台继续使用 attribute,其他平台使用 className)
+                if(
+                  process.env.UNI_PLATFORM === 'h5' ||
+                  (
+                    process.env.UNI_PLATFORM === 'app-plus' &&
+                    process.env.UNI_USING_V3
+                  )
+                ){
                   selector.insertAfter(node, selectorParser.attribute({
                       attribute: id
                   }));