Use Object Spread Syntax (#7777)

* Use Object Spread Syntax

* Nits

packages/babel-core/src/transformation/normalize-opts.js

@@ -22,36 +22,38 @@ export default function normalizeOptions(config: ResolvedConfig): {} {
 
   const opts = config.options;
 
-  const options = Object.assign({}, opts, {
-    parserOpts: Object.assign(
-      {
-        sourceType:
-          path.extname(filenameRelative) === ".mjs" ? "module" : sourceType,
-        sourceFileName: filename,
-        plugins: [],
-      },
-      opts.parserOpts,
-    ),
-    generatorOpts: Object.assign(
-      {
-        // General generator flags.
-        filename,
-        auxiliaryCommentBefore: opts.auxiliaryCommentBefore,
-        auxiliaryCommentAfter: opts.auxiliaryCommentAfter,
-        retainLines: opts.retainLines,
-        comments,
-        shouldPrintComment: opts.shouldPrintComment,
-        compact,
-        minified: opts.minified,
+  const options = {
+    ...opts,
 
-        // Source-map generation flags.
-        sourceMaps,
-        sourceRoot,
-        sourceFileName,
-      },
-      opts.generatorOpts,
-    ),
-  });
+    parserOpts: {
+      sourceType:
+        path.extname(filenameRelative) === ".mjs" ? "module" : sourceType,
+
+      sourceFileName: filename,
+      plugins: [],
+      ...opts.parserOpts,
+    },
+
+    generatorOpts: {
+      // General generator flags.
+      filename,
+
+      auxiliaryCommentBefore: opts.auxiliaryCommentBefore,
+      auxiliaryCommentAfter: opts.auxiliaryCommentAfter,
+      retainLines: opts.retainLines,
+      comments,
+      shouldPrintComment: opts.shouldPrintComment,
+      compact,
+      minified: opts.minified,
+
+      // Source-map generation flags.
+      sourceMaps,
+
+      sourceRoot,
+      sourceFileName,
+      ...opts.generatorOpts,
+    },
+  };
 
   for (const plugins of config.passes) {
     for (const plugin of plugins) {