Add optional chaining (#8052)

* Add plugin-proposal-optional-chaining

* Use optional chaining to provide error fallback

app/scripts/metamask-controller.js

@@ -257,7 +257,7 @@ export default class MetamaskController extends EventEmitter {
           const metamaskState = await this.getState()
           backEndMetaMetricsEvent(metamaskState, {
             customVariables: {
-              errorMessage: txMeta.simulationFails.reason,
+              errorMessage: txMeta.simulationFails?.reason,
             },
             eventOpts: {
               category: 'backend',

babel.config.js

@@ -19,6 +19,7 @@ module.exports = function (api) {
       '@babel/plugin-transform-runtime',
       '@babel/plugin-proposal-class-properties',
       '@babel/plugin-proposal-object-rest-spread',
+      '@babel/plugin-proposal-optional-chaining',
     ],
   }
 }

package.json

@@ -172,6 +172,7 @@
     "@babel/core": "^7.5.5",
     "@babel/plugin-proposal-class-properties": "^7.5.5",
     "@babel/plugin-proposal-object-rest-spread": "^7.5.5",
+    "@babel/plugin-proposal-optional-chaining": "^7.8.3",
     "@babel/plugin-transform-runtime": "^7.5.5",
     "@babel/preset-env": "^7.5.5",
     "@babel/preset-react": "^7.0.0",

yarn.lock

@@ -434,6 +434,14 @@
     "@babel/helper-plugin-utils" "^7.0.0"
     "@babel/plugin-syntax-optional-catch-binding" "^7.2.0"
 
+"@babel/plugin-proposal-optional-chaining@^7.8.3":
+  version "7.8.3"
+  resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-optional-chaining/-/plugin-proposal-optional-chaining-7.8.3.tgz#ae10b3214cb25f7adb1f3bc87ba42ca10b7e2543"
+  integrity sha512-QIoIR9abkVn+seDE3OjA08jWcs3eZ9+wJCKSRgo3WdEU2csFYgdScb+8qHB3+WXsGJD55u+5hWCISI7ejXS+kg==
+  dependencies:
+    "@babel/helper-plugin-utils" "^7.8.3"
+    "@babel/plugin-syntax-optional-chaining" "^7.8.0"
+
 "@babel/plugin-proposal-unicode-property-regex@^7.4.4":
   version "7.4.4"
   resolved "https://registry.yarnpkg.com/@babel/plugin-proposal-unicode-property-regex/-/plugin-proposal-unicode-property-regex-7.4.4.tgz#501ffd9826c0b91da22690720722ac7cb1ca9c78"
@@ -499,6 +507,13 @@
   dependencies:
     "@babel/helper-plugin-utils" "^7.0.0"
 
+"@babel/plugin-syntax-optional-chaining@^7.8.0":
+  version "7.8.3"
+  resolved "https://registry.yarnpkg.com/@babel/plugin-syntax-optional-chaining/-/plugin-syntax-optional-chaining-7.8.3.tgz#4f69c2ab95167e0180cd5336613f8c5788f7d48a"
+  integrity sha512-KoK9ErH1MBlCPxV0VANkXW2/dw4vlbGDrFgz8bmUsBGYkFRcbRwMh6cIJubdPrkxRwuGdtCk0v/wPTKbQgBjkg==
+  dependencies:
+    "@babel/helper-plugin-utils" "^7.8.0"
+
 "@babel/plugin-transform-arrow-functions@^7.2.0":
   version "7.2.0"
   resolved "https://registry.yarnpkg.com/@babel/plugin-transform-arrow-functions/-/plugin-transform-arrow-functions-7.2.0.tgz#9aeafbe4d6ffc6563bf8f8372091628f00779550"