Fix optional chaining and nullish coalescing support (#8526)

Author: ianschmitz

packages/babel-preset-react-app/create.js

@@ -185,6 +185,12 @@ module.exports = function(api, opts, env) {
           removeImport: true,
         },
       ],
+      // Optional chaining and nullish coalescing are supported in @babel/preset-env,
+      // but not yet supported in webpack due to support missing from acorn.
+      // These can be removed once webpack has support.
+      // See https://github.com/facebook/create-react-app/issues/8445#issuecomment-588512250
+      require('@babel/plugin-proposal-optional-chaining').default,
+      require('@babel/plugin-proposal-nullish-coalescing-operator').default,
     ].filter(Boolean),
     overrides: [
       isFlowEnabled && {

packages/babel-preset-react-app/package.json

@@ -24,7 +24,9 @@
     "@babel/core": "7.8.4",
     "@babel/plugin-proposal-class-properties": "7.8.3",
     "@babel/plugin-proposal-decorators": "7.8.3",
+    "@babel/plugin-proposal-nullish-coalescing-operator": "7.8.3",
     "@babel/plugin-proposal-numeric-separator": "7.8.3",
+    "@babel/plugin-proposal-optional-chaining": "7.8.3",
     "@babel/plugin-transform-flow-strip-types": "7.8.3",
     "@babel/plugin-transform-react-display-name": "7.8.3",
     "@babel/plugin-transform-runtime": "7.8.3",