Replace merge utility with spread syntax.

src/createConfig.js

@@ -8,7 +8,6 @@ import get from 'lodash/get';
 import omit from 'lodash/omit';
 
 import mapParentConfig from './mapParentConfig';
-import { merge } from './utils';
 
 const webpackMerge = strategy({
   entry: 'append',
@@ -28,7 +27,7 @@ const prepare = config => {
   // plugins are ommited by default too.
   // It's not ideal, but it's better to let the user make a conscious choice about it.
   const props = ['context', 'plugins', 'entry', 'output'];
-  return merge(omit(config, props), { plugins });
+  return { ...omit(config, props), plugins };
 };
 
 export const _createConfig = cacheDir => (settings, rawParentConfig) => {

src/createSettings.js

@@ -1,6 +1,5 @@
 import get from 'lodash/get';
 import isNil from 'lodash/isNil';
-import { merge } from './utils';
 import createHash from './createHash';
 import normalizeEntry from './normalizeEntry';
 import getEnv from './getEnv';
@@ -31,16 +30,19 @@ export const _createSettings = getEnv => ({ originalSettings, index, parentConfi
     config: {},
   };
 
-  const settings = merge(defaults, otherSettings, {
+  const settings = {
+    ...defaults,
+    ...otherSettings,
     entry: normalizeEntry(entry),
     id: getInstanceId(index),
     env: getEnv(env),
     inherit: isNil(inherit) ? false : inherit,
-  });
+  };
 
-  return merge(settings, {
+  return {
+    ...settings,
     hash: createHash(settings),
-  });
+  };
 };
 
 export default _createSettings(getEnv);

src/plugin.js

@@ -6,7 +6,7 @@ import { RawSource } from 'webpack-sources';
 import path from 'path';
 
 import { cacheDir, getManifestPath, getInjectPath } from './paths';
-import { concat, merge, keys } from './utils/index.js';
+import { concat, keys } from './utils/index.js';
 import createCompileIfNeeded from './createCompileIfNeeded';
 import createConfig from './createConfig';
 import createMemory from './createMemory';
@@ -103,7 +103,7 @@ class AutoDLLPlugin {
         };
       }, {});
 
-      compilation.assets = merge(compilation.assets, dllAssets);
+      compilation.assets = { ...compilation.assets, ...dllAssets };
 
       callback();
     });

src/utils/index.js

@@ -1,4 +1,3 @@
 export { default as safeClone } from './safeClone';
 export const concat = Array.prototype.concat.bind([]);
-export const merge = (...args) => Object.assign({}, ...args);
 export const keys = Object.keys;