Persist lost identities to storage for later analysis

app/scripts/controllers/preferences.js

@@ -28,6 +28,7 @@ class PreferencesController {
       featureFlags: {},
       currentLocale: opts.initLangCode,
       identities: {},
+      lostIdentities: {},
     }, opts.initState)
     this.store = new ObservableStore(initState)
   }
@@ -106,18 +107,19 @@ class PreferencesController {
    * @returns {Promise<string>} selectedAddress the selected address.
    */
   syncAddresses (addresses) {
-    const identities = this.store.getState().identities
+    let { identities, lostIdentities } = this.store.getState()
 
     Object.keys(identities).forEach((identity) => {
       if (!addresses.includes(identity)) {
         delete identities[identity]
+        lostIdentities[identity] = identities[identity]
 
         // TODO: Report the bug to Sentry including the now-lost identity.
         alert('Error 4486: MetaMask has encountered a very strange error. Please open a support issue immediately at support@metamask.io.')
       }
     })
 
-    this.store.updateState({ identities })
+    this.store.updateState({ identities, lostIdentities })
     this.addAddresses(addresses)
 
     let selected = this.getSelectedAddress()

app/scripts/lib/4486-notifier.js

@@ -0,0 +1,29 @@
+class BugNotifier {
+  notify (message) {
+
+    postData('http://example.com/answer', {answer: 42})
+      .then(data => console.log(data)) // JSON from `response.json()` call
+      .catch(error => console.error(error))
+  }
+}
+
+function postData(url, data) {
+  // Default options are marked with *
+  return fetch(url, {
+    body: JSON.stringify(data), // must match 'Content-Type' header
+    cache: 'no-cache', // *default, no-cache, reload, force-cache, only-if-cached
+    credentials: 'same-origin', // include, same-origin, *omit
+    headers: {
+      'user-agent': 'Mozilla/4.0 MDN Example',
+      'content-type': 'application/json'
+    },
+    method: 'POST', // *GET, POST, PUT, DELETE, etc.
+    mode: 'cors', // no-cors, cors, *same-origin
+    redirect: 'follow', // manual, *follow, error
+    referrer: 'no-referrer', // *client, no-referrer
+  })
+  .then(response => response.json()) // parses response to JSON
+}
+
+module.exports = BugNotifier
+