fix: remove Object.assign, fixes #1226

src/adapters/preact.js

@@ -1,4 +1,4 @@
-import configuration from '../configuration'
+import { setConfiguration } from '../configuration'
 
 const tune = {
   allowSFC: false,
@@ -7,7 +7,7 @@ const tune = {
 export const preactAdapter = (instance, resolveType) => {
   const oldHandler = instance.options.vnode
 
-  Object.assign(configuration, tune)
+  setConfiguration(tune)
 
   instance.options.vnode = vnode => {
     vnode.nodeName = resolveType(vnode.nodeName)

src/configuration.js

@@ -44,4 +44,13 @@ export const internalConfiguration = {
   disableProxyCreation: false,
 }
 
+export const setConfiguration = config => {
+  // not using Object.assing for IE11 compliance
+  for (const i in config) {
+    if (config.hasOwnProperty(i)) {
+      configuration[i] = config[i]
+    }
+  }
+}
+
 export default configuration

src/internal/getReactStack.js

@@ -36,10 +36,10 @@ const markUpdate = ({ fiber }) => {
   }
 
   if (fiber.memoizedProps && typeof fiber.memoizedProps === 'object') {
-    fiber.memoizedProps = Object.assign(
-      { cacheBusterProp: true },
-      fiber.memoizedProps,
-    )
+    fiber.memoizedProps = {
+      cacheBusterProp: true,
+      ...fiber.memoizedProps,
+    }
   }
 }
 

src/utils.dev.js

@@ -3,7 +3,7 @@ import {
   getProxyByType,
   setComponentOptions,
 } from './reconciler/proxies'
-import configuration from './configuration'
+import { setConfiguration } from './configuration'
 import { hotComponentCompare } from './reconciler/componentComparator'
 
 const getProxyOrType = type => {
@@ -25,4 +25,4 @@ export const cold = type => {
 export const configureComponent = (component, options) =>
   setComponentOptions(component, options)
 
-export const setConfig = config => Object.assign(configuration, config)
+export const setConfig = config => setConfiguration(config)