fix: syncMode - default: use append strategy when using dev server, overwrite strategy when using build.

Author: xiaweiss

src/core/context.ts

@@ -80,7 +80,6 @@ export class Context {
       return
 
     this._server = server
-    this._removeUnused = this.options.syncMode !== 'append'
     this.setupWatcher(server.watcher)
   }
 

src/core/options.ts

@@ -73,6 +73,11 @@ export function resolveOptions(options: Options, root: string): ResolvedOptions
       throw new Error('[unplugin-vue-components] `extensions` option is required to search for components')
   }
 
+  // syncMode - `default`: use `append` strategy when using dev server, `overwrite` strategy when using build.
+  if (resolved.syncMode === 'default') {
+    resolved.syncMode = process.env.NODE_ENV === 'development' ? 'append' : 'overwrite'
+  }
+
   resolved.globsExclude = toArray(resolved.globsExclude || [])
     .map(i => resolveGlobsExclude(root, i))