specify sourcemap per file instead

Author: Peerapong Maitriwong

rollup.config.ts

@@ -12,10 +12,9 @@ const libraryName = '--libraryname--'
 export default {
   input: `src/${libraryName}.ts`,
   output: [
-    { file: pkg.main, name: camelCase(libraryName), format: 'umd' },
-    { file: pkg.module, format: 'es' },
+    { file: pkg.main, name: camelCase(libraryName), format: 'umd', sourcemap: true },
+    { file: pkg.module, format: 'es', sourcemap: true },
   ],
-  sourcemap: true,
   // Indicate here external modules you don't wanna include in your bundle (i.e.: 'lodash')
   external: [],
   watch: {