Use Object Spread Syntax (#7777)

* Use Object Spread Syntax

* Nits

packages/babel-core/src/config/config-chain.js

@@ -480,7 +480,9 @@ function emptyChain(): ConfigChain {
 }
 
 function normalizeOptions(opts: ValidatedOptions): ValidatedOptions {
-  const options = Object.assign({}, opts);
+  const options = {
+    ...opts,
+  };
   delete options.extends;
   delete options.env;
   delete options.plugins;

packages/babel-core/src/config/full.js

@@ -174,7 +174,10 @@ const loadDescriptor = makeWeakCache(
 
     let item = value;
     if (typeof value === "function") {
-      const api = Object.assign({}, context, makeAPI(cache));
+      const api = {
+        ...context,
+        ...makeAPI(cache),
+      };
       try {
         item = value(api, options, dirname);
       } catch (e) {
@@ -229,9 +232,13 @@ const instantiatePlugin = makeWeakCache(
   ): Plugin => {
     const pluginObj = validatePluginObject(value);
 
-    const plugin = Object.assign({}, pluginObj);
+    const plugin = {
+      ...pluginObj,
+    };
     if (plugin.visitor) {
-      plugin.visitor = traverse.explode(Object.assign({}, plugin.visitor));
+      plugin.visitor = traverse.explode({
+        ...plugin.visitor,
+      });
     }
 
     if (plugin.inherits) {

packages/babel-core/src/transform-file-sync.js

@@ -12,7 +12,10 @@ export default function transformFileSync(
   if (opts == null) {
     options = { filename };
   } else if (opts && typeof opts === "object") {
-    options = Object.assign({}, opts, { filename });
+    options = {
+      ...opts,
+      filename,
+    };
   }
 
   const config = loadConfig(options);

packages/babel-core/src/transform-file.js

@@ -19,7 +19,10 @@ export default ((function transformFile(filename, opts, callback) {
   if (opts == null) {
     options = { filename };
   } else if (opts && typeof opts === "object") {
-    options = Object.assign({}, opts, { filename });
+    options = {
+      ...opts,
+      filename,
+    };
   }
 
   process.nextTick(() => {

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) {