Description
When using this CLI plugin, there are duplicated CSS rules when using CSS modules and the "composes" feature. This seems to be caused by the critical CSS that's inlined into the <head> and is both happening in development and production (main issue).
I've created the following test repo (https://github.com/mrksbnch/vue-ssr-css-issue) that I created using vue create (Vue router as the only feature) and vue add @akryum/vue-cli-plugin-ssr. Afterwards, I added a test.css file in the folder assets and composed (<style module>) two style declarations from that file in Home.vue and HelloWorld.vue.
You can see the duplicated rules after running npm run ssr:serve or npm run ssr:build and npm run ssr:start in the dev tools:
Both CSS rules are inlined on the server side (<style data-vue-ssr-id>):
This is just a simple test repo with only one CSS rule. In a proper app this will cause a lot (!) of duplicated CSS rules and increase the file size by quite a bit. I've tested it with a simple app and I noticed some rules being duplicated 5 or 6 times.